Refactor tracing context (#139)

* Delete `ISkyWalkingClient` interface

* Use segment protocol V2

* Forget the old api. All context apis will be overwritten.

* Add segments define

* Add some apis

* Add carrierParser

* Add SegmentContextAccessor API

* Add SampledDelegate interface

* Add thread-safe  SamplerChainBuilder

* Add SegmentContextFactory

* Add ITracingContext Interface

* Refactoring the core API for tracing context

* remove utils package

* Resolve issue #57 : Provide percentage-based sampling

* Refactor HttpClient Tracing

* Fix header carrier

* Add async exitSpan sample

* Add Task.WhenAll sample

* Refactor EntityFrameworkCore tracing

* Refactor SqlClient & CAP Tracing

* Refactor Asp.Net tracing

* Remove outdated APIs

sample/SkyWalking.Sample.AspNet/skywalking.json

 {
   "SkyWalking": {
-    "ApplicationCode": "SkyWalking.Sample.AspNet",
-    "SpanLimitPerSegment": 300,
-    "Sampling": {
-      "SamplePer3Secs": -1
-    },
+    "ServiceName": "aspnet-sample",
     "Logging": {
-      "Level": "Information",
-      "FilePath": "logs\\SkyWalking-{Date}.log"
+      "Level": "Debug",
+      "FilePath": "/tmp/logs/SkyWalking-{Date}.log"
     },
     "Transport": {
       "Interval": 3000,
-      "PendingSegmentLimit": 30000,
-      "PendingSegmentTimeout": 1000,
       "gRPC": {
         "Servers": "localhost:11800",
-        "Timeout": 2000,
+        "Timeout": 10000,
         "ConnectTimeout": 10000
       }
     }

sample/SkyWalking.Sample.Backend/Controllers/DelayController.cs

+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc;
+
+namespace SkyWalking.Sample.Backend.Controllers
+{
+    [Route("api/[controller]")]
+    public class DelayController : Controller
+    {
+        // GET
+        [HttpGet("{delay}")]
+        public async Task<string> Get(int delay)
+        {
+            await Task.Delay(delay);
+            return $"delay {delay}ms";
+        }
+    }
+}
\ No newline at end of file

sample/SkyWalking.Sample.Backend/Sampling/CustomSamplingInterceptor.cs

+using SkyWalking.Tracing;
+
+namespace SkyWalking.Sample.Backend.Sampling
+{
+    public class CustomSamplingInterceptor : ISamplingInterceptor
+    {
+        public int Priority { get; } = 0;
+        
+        public bool Invoke(SamplingContext samplingContext, Sampler next)
+        {
+            return next(samplingContext);
+        }
+    }
+}
\ No newline at end of file

sample/SkyWalking.Sample.Backend/Startup.cs

@@ -5,6 +5,8 @@ using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using SkyWalking.Sample.Backend.Models;
+using SkyWalking.Sample.Backend.Sampling;
+using SkyWalking.Tracing;
 
 namespace SkyWalking.Sample.Backend
 {
@@ -26,6 +28,8 @@ namespace SkyWalking.Sample.Backend
             sqliteConnection.Open();
             
             services.AddEntityFrameworkSqlite().AddDbContext<SampleDbContext>(c => c.UseSqlite(sqliteConnection));
+
+            services.AddSingleton<ISamplingInterceptor, CustomSamplingInterceptor>();
         }
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.

sample/SkyWalking.Sample.Frontend/Controllers/ValuesController.cs

@@ -9,11 +9,21 @@ namespace SkyWalking.Sample.Frontend.Controllers
     public class ValuesController : Controller
     {
         // GET api/values
-        [HttpGet("/values")]
+        [HttpGet]
         public async Task<IEnumerable<string>> Get()
         {
             await new HttpClient().GetAsync("http://localhost:5002/api/values");
-            return new string[] { "value1", "value2" };
+            return new string[] {"value1", "value2"};
+        }
+
+        [HttpGet("{id}")]
+        public async Task<string> Get(int id)
+        {
+            var client = new HttpClient();
+            Task.WhenAll(client.GetAsync("http://localhost:5002/api/delay/2000"),
+                client.GetAsync("http://localhost:5002/api/values"),
+                client.GetAsync("http://localhost:5002/api/delay/200"));
+            return await client.GetStringAsync("http://localhost:5002/api/delay/100");
         }
     }
 }
\ No newline at end of file

sample/SkyWalking.Sample.Frontend/appsettings.json

@@ -13,7 +13,7 @@
     }
   },
   "SkyWalking": {
-    "ApplicationCode": "asp-net-core-frontend"
+    "ServiceName": "asp-net-core-frontend"
   }
 }
 

src/SkyWalking.Abstractions/Context/IContextCarrier.cs → src/SkyWalking.Abstractions/Common/Components.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,44 +16,26 @@
  *
  */
 
-using System.Collections.Generic;
-using SkyWalking.Context.Ids;
-
-namespace SkyWalking.Context
+namespace SkyWalking.Common
 {
-    public interface IContextCarrier
+    public static class Components
     {
+        public static readonly StringOrIntValue ASPNETCORE= new StringOrIntValue("AspNetCore");
 
-        DistributedTraceId DistributedTraceId { get; }
-
-        int EntryApplicationInstanceId { get; set; }
-
-        string EntryOperationName { get; set; }
-        
-        int EntryOperationId { get; set; }
-
-        int ParentApplicationInstanceId { get; set; }
-
-        string ParentOperationName { get; set; }
-        
-        int ParentOperationId { get; set; }
-
-        string PeerHost { get; set; }
-        
-        int PeerId { get; set; }
+        public static readonly StringOrIntValue HTTPCLIENT = new StringOrIntValue("HttpClient");
         
-        int SpanId { get; set; }
+        public static readonly StringOrIntValue ENTITYFRAMEWORKCORE = new StringOrIntValue("EntityFrameworkCore");
         
-        ID TraceSegmentId { get; set; }
+        public static readonly StringOrIntValue SQLCLIENT = new StringOrIntValue("SqlClient");
         
-        bool IsValid { get; }
+        public static readonly StringOrIntValue CAP = new StringOrIntValue("CAP");
         
-        IContextCarrier Deserialize(string text);
+        public static readonly StringOrIntValue ENTITYFRAMEWORKCORE_SQLITE = new StringOrIntValue("EntityFrameworkCore.Sqlite");
         
-        string Serialize();
+        public static readonly StringOrIntValue POMELO_ENTITYFRAMEWORKCORE_MYSQL = new StringOrIntValue("Pomelo.EntityFrameworkCore.MySql");
         
-        CarrierItem Items { get; }
+        public static readonly StringOrIntValue NPGSQL_ENTITYFRAMEWORKCORE_POSTGRESQL = new StringOrIntValue("Npgsql.EntityFrameworkCore.PostgreSQL");
         
-        void SetDistributedTraceIds(IEnumerable<DistributedTraceId> distributedTraceIds);
+        public static readonly StringOrIntValue ASPNET = new StringOrIntValue("AspNet");
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/NullableValue.cs → src/SkyWalking.Abstractions/Common/NullableValue.cs

@@ -16,7 +16,7 @@
  *
  */
 
-namespace SkyWalking
+namespace SkyWalking.Common
 {
     public struct NullableValue
     {

src/SkyWalking.Abstractions/StringOrIntValue.cs → src/SkyWalking.Abstractions/Common/StringOrIntValue.cs

@@ -16,7 +16,7 @@
  *
  */
 
-namespace SkyWalking
+namespace SkyWalking.Common
 {
     public struct StringOrIntValue
     {
@@ -29,6 +29,8 @@ namespace SkyWalking
             _stringValue = null;
         }
 
+        public bool HasValue => HasIntValue || HasStringValue;
+
         public bool HasIntValue => _intValue != 0;
         
         public bool HasStringValue => _stringValue != null;
@@ -53,5 +55,11 @@ namespace SkyWalking
         {
             return (_stringValue, _intValue);
         }
+
+        public override string ToString()
+        {
+            if (HasIntValue) return _intValue.ToString();
+            return _stringValue;
+        }
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Context/IContextSnapshot.cs → src/SkyWalking.Abstractions/Common/Tags.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,30 +16,27 @@
  *
  */
 
-using SkyWalking.Context.Ids;
-
-namespace SkyWalking.Context
+namespace SkyWalking.Common
 {
-    public interface IContextSnapshot
+    public static class Tags
     {
-        string EntryOperationName { get; set; }
+        public static readonly string URL = "url";
         
-        string ParentOperationName { get; set; }
+        public static readonly string PATH = "path";
 
-        DistributedTraceId DistributedTraceId { get; }
 
-        int EntryApplicationInstanceId { get; set; }
+        public static readonly string HTTP_METHOD = "http.method";
 
-        int SpanId { get; }
+        public static readonly string STATUS_CODE = "status_code";
 
-        bool IsFromCurrent { get; }
+        public static readonly string DB_TYPE = "db.type";
 
-        bool IsValid { get; }
+        public static readonly string DB_INSTANCE = "db.instance";
         
-        ID TraceSegmentId { get; }
+        public static readonly string DB_STATEMENT = "db.statement";
         
-        int EntryOperationId { set; }
+        public static readonly string DB_BIND_VARIABLES = "db.bind_vars";
 
-        int ParentOperationId { set; }
+        public static readonly string MQ_TOPIC = "mq.topic";
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Components/ComponentsDefine.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Collections.Generic;
-
-namespace SkyWalking.Components
-{
-    public class ComponentsDefine
-    {
-        public static readonly IComponent HttpClient = new OfficialComponent(2, "HttpClient");
-        
-        public static readonly IComponent AspNetCore = new OfficialComponent(3001, "AspNetCore");
-
-        public static readonly IComponent EntityFrameworkCore = new OfficialComponent(3002, "EntityFrameworkCore");
-
-        public static readonly IComponent SqlClient = new OfficialComponent(3003, "SqlClient");
-        
-        public static readonly IComponent CAP = new OfficialComponent(3004, "CAP");
-        
-        public static readonly IComponent StackExchange_Redis = new OfficialComponent(3005, "StackExchange.Redis");
-        
-        public static readonly IComponent SqlServer = new OfficialComponent(3006, "SqlServer");
-        
-        public static readonly IComponent Npgsql = new OfficialComponent(3007, "Npgsql");
-        
-        public static readonly IComponent MySqlConnector = new OfficialComponent(3008, "MySqlConnector");
-        
-        public static readonly IComponent EntityFrameworkCore_InMemory = new OfficialComponent(3009, "EntityFrameworkCore.InMemory");
-        
-        public static readonly IComponent EntityFrameworkCore_SqlServer = new OfficialComponent(3010, "EntityFrameworkCore.SqlServer");
-        
-        public static readonly IComponent EntityFrameworkCore_Sqlite = new OfficialComponent(3011, "EntityFrameworkCore.Sqlite");
-        
-        public static readonly IComponent Pomelo_EntityFrameworkCore_MySql = new OfficialComponent(3012, "Pomelo.EntityFrameworkCore.MySql");
-        
-        public static readonly IComponent Npgsql_EntityFrameworkCore_PostgreSQL = new OfficialComponent(3013, "Npgsql.EntityFrameworkCore.PostgreSQL");
-        
-        public static readonly IComponent InMemoryDatabase = new OfficialComponent(3014, "InMemoryDatabase");
-        
-        public static readonly IComponent AspNet = new OfficialComponent(3015, "AspNet");
-
-        public static readonly IComponent MySqlData = new OfficialComponent(3016, "MySql.Data");
-    }
-}

src/SkyWalking.Abstractions/Config/InstrumentationConfig.cs → src/SkyWalking.Abstractions/Config/InstrumentConfig.cs

@@ -21,7 +21,7 @@ using System;
 namespace SkyWalking.Config
 {
     [Config("SkyWalking")]
-    public class InstrumentationConfig
+    public class InstrumentConfig
     {
         public string Namespace { get; set; }
 
@@ -30,6 +30,13 @@ namespace SkyWalking.Config
         
         public string ServiceName { get; set; }
         
-        public int SpanLimitPerSegment { get; set; } = 300;
+        public string[] HeaderVersions { get; set; }
+    }
+
+    public static class HeaderVersions
+    {
+        public static string SW3 { get; } = "sw3";
+        
+        public static string SW6 { get; } = "sw6";
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Config/SamplingConfig.cs

@@ -22,5 +22,7 @@ namespace SkyWalking.Config
     public class SamplingConfig
     {
         public int SamplePer3Secs { get; set; } = -1;
+
+        public double Percentage { get; set; } = -1d;
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Config/TransportConfig.cs

@@ -21,7 +21,7 @@ namespace SkyWalking.Config
     [Config("SkyWalking", "Transport")]
     public class TransportConfig
     {
-        public int PendingSegmentLimit { get; set; } = 30000;
+        public int QueueSize { get; set; } = 30000;
 
         /// <summary>
         /// Flush Interval Millisecond
@@ -31,7 +31,7 @@ namespace SkyWalking.Config
         /// <summary>
         /// Data queued beyond this time will be discarded.
         /// </summary>
-        public int PendingSegmentTimeout { get; set; } = 1000;
+        public int BatchSize { get; set; } = 3000;
 
         public string ProtocolVersion { get; set; } = ProtocolVersions.V6;
     }

src/SkyWalking.Abstractions/Context/IInjectable.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System;
-
-namespace SkyWalking.Context
-{
-    public interface IInjectable
-    {
-        IContextCarrier GetCarrier();
-
-        /// <summary>
-        /// @return peer, represent ipv4, ipv6, hostname, or cluster addresses list.
-        /// </summary>
-        /// <returns></returns>
-        String GetPeer();
-    }
-}

src/SkyWalking.Abstractions/Context/Ids/DistributedTraceId.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-
-using System;
-using SkyWalking.Transport;
-
-namespace SkyWalking.Context.Ids
-{
-
-    /// <inheritdoc />
-    /// <summary>
-    /// The <code>DistributedTraceId</code> presents a distributed call chain.
-    /// This call chain has an unique (service) entrance,
-    /// such as: Service : http://www.skywalking.com/cust/query, all the remote, called behind this service, rest remote,
-    /// db executions, are using the same <code>DistributedTraceId</code> even in different CLR process.
-    /// The <code>DistributedTraceId</code> contains only one string, and can NOT be reset, creating a new instance is the only option.
-    /// </summary>
-    public abstract class DistributedTraceId : IEquatable<DistributedTraceId>
-    {
-        private readonly ID _id;
-
-        protected DistributedTraceId(ID id)
-        {
-            _id = id;
-        }
-
-        protected DistributedTraceId(string id)
-        {
-            _id = new ID(id);
-        }
-
-        public string Encode => _id?.Encode;
-
-        public UniqueIdRequest ToUniqueId() => _id?.Transform();
-
-        public bool Equals(DistributedTraceId other)
-        {
-            if (other == null)
-                return false;
-            return _id?.Equals(other._id) ?? other._id == null;
-        }
-
-        public override bool Equals(object obj)
-        {
-            var id = obj as DistributedTraceId;
-            return Equals(id);
-        }
-
-        public override int GetHashCode() => _id != null ? _id.GetHashCode() : 0;
-
-        public override string ToString() => _id?.ToString();
-    }
-}

src/SkyWalking.Abstractions/Context/Ids/ID.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System;
-using SkyWalking.Transport;
-
-namespace SkyWalking.Context.Ids
-{
-    public class ID : IEquatable<ID>
-    {
-        private readonly long _part1;
-        private readonly long _part2;
-        private readonly long _part3;
-        private string _encoding;
-
-        public bool IsValid { get; }
-
-        public string Encode => _encoding ?? (_encoding = ToString());
-
-        public ID(long part1, long part2, long part3)
-        {
-            _part1 = part1;
-            _part2 = part2;
-            _part3 = part3;
-            IsValid = true;
-        }
-
-        public ID(string encodingString)
-        {
-            if (encodingString == null)
-            {
-                throw new ArgumentNullException(nameof(encodingString));
-            }
-            string[] idParts = encodingString.Split("\\.".ToCharArray(), 3);
-            for (int part = 0; part < 3; part++)
-            {
-                if (part == 0)
-                {
-                    IsValid = long.TryParse(idParts[part], out _part1);
-                }
-                else if (part == 1)
-                {
-                    IsValid = long.TryParse(idParts[part], out _part2);
-                }
-                else
-                {
-                    IsValid = long.TryParse(idParts[part], out _part3);
-                }
-                if (!IsValid)
-                {
-                    break;
-                }
-            }
-        }
-
-        public override string ToString()
-        {
-            return $"{_part1}.{_part2}.{_part3}";
-        }
-
-        public override int GetHashCode()
-        {
-            var result = (int)(_part1 ^ (_part1 >> 32));
-            result = 31 * result + (int)(_part2 ^ (_part2 >> 32));
-            result = 31 * result + (int)(_part3 ^ (_part3 >> 32));
-            return result;
-        }
-
-        public override bool Equals(object obj)
-        {
-            var id = obj as ID;
-            return Equals(id);
-        }
-
-        public bool Equals(ID other)
-        {
-            if (other == null)
-                return false;
-            if (this == other)
-                return true;
-            if (_part1 != other._part1)
-                return false;
-            if (_part2 != other._part2)
-                return false;
-            return _part3 == other._part3;
-        }
-
-        public UniqueIdRequest Transform()
-        {
-            var uniqueId = new UniqueIdRequest {Part1 = _part1, Part2 = _part2, Part3 = _part3};
-            return uniqueId;
-        }
-    }
-}

src/SkyWalking.Abstractions/Context/Trace/AbstractTracingSpan.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System;
-using System.Collections.Generic;
-using SkyWalking.Transport;
-using SkyWalking.Components;
-
-namespace SkyWalking.Context.Trace
-{
-    /// <summary>
-    /// The <code>AbstractTracingSpan</code> represents a group of {@link ISpan} implementations, which belongs a real distributed trace.
-    /// </summary>
-    public abstract class AbstractTracingSpan : ISpan
-    {
-        protected readonly int _spanId;
-        protected readonly int _parnetSpanId;
-        protected Dictionary<string, string> _tags;
-        protected string _operationName;
-        protected int _operationId;
-        protected SpanLayer? _layer;
-
-        /// <summary>
-        /// The start time of this Span.
-        /// </summary>
-        protected long _startTime;
-
-        /// <summary>
-        /// The end time of this Span.
-        /// </summary>
-        protected long _endTime;
-
-        protected bool _errorOccurred = false;
-
-        protected int _componentId = 0;
-
-        protected string _componentName;
-
-        /// <summary>
-        /// Log is a concept from OpenTracing spec. <p> {@see https://github.com/opentracing/specification/blob/master/specification.md#log-structured-data}
-        /// </summary>
-        protected ICollection<LogDataEntity> _logs;
-
-        /// <summary>
-        /// The refs of parent trace segments, except the primary one. For most RPC call, {@link #refs} contains only one
-        /// element, but if this segment is a start span of batch process, the segment faces multi parents, at this moment,
-        /// we use this {@link #refs} to link them.
-        /// </summary>
-        protected ICollection<ITraceSegmentRef> _refs;
-
-        protected AbstractTracingSpan(int spanId, int parentSpanId, string operationName)
-        {
-            _operationName = operationName;
-            _spanId = spanId;
-            _parnetSpanId = parentSpanId;
-        }
-
-        protected AbstractTracingSpan(int spanId, int parentSpanId, int operationId)
-        {
-            _operationName = null;
-            _operationId = operationId;
-            _spanId = spanId;
-            _parnetSpanId = parentSpanId;
-        }
-
-        public abstract bool IsEntry { get; }
-
-        public abstract bool IsExit { get; }
-
-        public virtual int SpanId => _spanId;
-
-        public virtual string OperationName
-        {
-            get => _operationName;
-            set
-            {
-                _operationName = value;
-                _operationId = 0;
-            }
-        }
-
-        public virtual int OperationId
-        {
-            get => _operationId;
-            set
-            {
-                _operationId = value;
-                _operationName = null;
-            }
-        }
-
-        public virtual ISpan SetComponent(IComponent component)
-        {
-            _componentId = component.Id;
-            return this;
-        }
-
-        public virtual ISpan SetComponent(string componentName)
-        {
-            _componentName = componentName;
-            return this;
-        }
-
-        public virtual ISpan Tag(string key, string value)
-        {
-            if (_tags == null)
-            {
-                _tags = new Dictionary<string, string>();
-            }
-
-            _tags.Add(key, value);
-            return this;
-        }
-
-        public virtual ISpan SetLayer(SpanLayer layer)
-        {
-            _layer = layer;
-            return this;
-        }
-
-        /// <summary>
-        /// Record an exception event of the current walltime timestamp.
-        /// </summary>
-        public virtual ISpan Log(Exception exception)
-        {
-            EnsureLogs();
-            _logs.Add(new LogDataEntity.Builder()
-                .Add("event", "error")
-                .Add("error.kind", exception.GetType().FullName)
-                .Add("message", exception.Message)
-                .Add("stack", exception.StackTrace)
-                .Build(DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()));
-            return this;
-        }
-
-        public virtual ISpan ErrorOccurred()
-        {
-            _errorOccurred = true;
-            return this;
-        }
-
-        public virtual ISpan Log(long timestamp, IDictionary<string, object> events)
-        {
-            EnsureLogs();
-            var builder = new LogDataEntity.Builder();
-            foreach (var @event in events)
-            {
-                builder.Add(@event.Key, @event.Value.ToString());
-            }
-
-            _logs.Add(builder.Build(timestamp));
-            return this;
-        }
-
-        public virtual ISpan Start()
-        {
-            _startTime = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
-            return this;
-        }
-
-        public virtual ISpan Start(long timestamp)
-        {
-            _startTime = timestamp;
-            return this;
-        }
-
-        public virtual void Ref(ITraceSegmentRef traceSegmentRef)
-        {
-            if (_refs == null)
-            {
-                _refs = new List<ITraceSegmentRef>();
-            }
-
-            if (!_refs.Contains(traceSegmentRef))
-            {
-                _refs.Add(traceSegmentRef);
-            }
-        }
-
-        /// <summary>
-        /// Finish the active Span. When it is finished, it will be archived by the given {@link TraceSegment}, which owners it
-        /// </summary>
-        /// <param name="owner"></param>
-        /// <returns></returns>
-        public virtual bool Finish(ITraceSegment owner)
-        {
-            _endTime = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
-            owner.Archive(this);
-            return true;
-        }
-
-        public virtual SpanRequest Transform()
-        {
-            var spanRequest = new SpanRequest
-            {
-                SpanId = _spanId,
-                ParentSpanId = _parnetSpanId,
-                StartTime = _startTime,
-                EndTime = _endTime,
-                OperationName = new StringOrIntValue(_operationId, _operationName),
-                Component = new StringOrIntValue(_componentId, _componentName),
-                IsError = _errorOccurred
-            };
-
-            if (IsEntry)
-            {
-                spanRequest.SpanType = 0;
-            }
-            else if (IsExit)
-            {
-                spanRequest.SpanType = 1;
-            }
-            else
-            {
-                spanRequest.SpanType = 2;
-            }
-
-            if (_layer.HasValue)
-            {
-                spanRequest.SpanLayer = (int) _layer.Value;
-            }
-
-
-            foreach (var tag in _tags)
-            {
-                spanRequest.Tags.Add(new KeyValuePair<string, string>(tag.Key, tag.Value));
-            }
-
-            if (_logs != null)
-            {
-                foreach (var logDataEntity in _logs)
-                {
-                    spanRequest.Logs.Add(logDataEntity.Transform());
-                }
-            }
-
-            if (_refs == null) return spanRequest;
-            foreach (var traceSegmentRef in _refs)
-            {
-                spanRequest.References.Add(traceSegmentRef.Transform());
-            }
-
-            return spanRequest;
-        }
-
-        private void EnsureLogs()
-        {
-            if (_logs == null)
-            {
-                _logs = new LinkedList<LogDataEntity>();
-            }
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Abstractions/Context/Trace/ISpan.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System;
-using System.Collections.Generic;
-using SkyWalking.Components;
-
-namespace SkyWalking.Context.Trace
-{
-    /// <summary>
-    /// The <code>AbstractSpan</code> represents the span's skeleton, which contains all open methods.
-    /// </summary>
-    public interface ISpan
-    {
-        /// <summary>
-        /// Set the component id, which defines in ComponentsDefine
-        /// </summary>
-        /// <param name="component"></param>
-        /// <returns></returns>
-        ISpan SetComponent(IComponent component);
-
-        /// <summary>
-        /// Only use this method in explicit skyWalking, like opentracing-skywalking-bridge. It it higher recommend
-        /// don't use this for performance consideration.
-        /// </summary>
-        /// <param name="componentName"></param>
-        /// <returns></returns>
-        ISpan SetComponent(string componentName);
-
-        /// <summary>
-        /// Set a key:value tag on the Span.
-        /// </summary>
-        /// <param name="key"></param>
-        /// <param name="value"></param>
-        /// <returns></returns>
-        ISpan Tag(string key, string value);
-
-        ISpan SetLayer(SpanLayer layer);
-
-        /// <summary>
-        /// Record an exception event of the current walltime timestamp.
-        /// </summary>
-        /// <param name="exception"></param>
-        /// <returns></returns>
-        ISpan Log(Exception exception);
-
-        ISpan ErrorOccurred();
-
-        bool IsEntry { get; }
-
-        bool IsExit { get; }
-
-        ISpan Log(long timestamp, IDictionary<string, object> @event);
-
-        ISpan Start();
-        
-        int SpanId { get; }
-        
-        string OperationName { get; set; }
-        
-        int OperationId { get; set; }
-
-        ISpan Start(long timestamp);
-        
-        void Ref(ITraceSegmentRef traceSegmentRef);
-    }
-}

src/SkyWalking.Abstractions/Context/Trace/ITraceSegment.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Collections.Generic;
-using SkyWalking.Transport;
-using SkyWalking.Context.Ids;
-
-namespace SkyWalking.Context.Trace
-{
-    public interface ITraceSegment
-    {
-        void Archive(AbstractTracingSpan finishedSpan);
-
-        ITraceSegment Finish(bool isSizeLimited);
-
-        int ApplicationId { get; }
-
-        int ApplicationInstanceId { get; }
-
-        IEnumerable<ITraceSegmentRef> Refs { get; }
-
-        IEnumerable<DistributedTraceId> RelatedGlobalTraces { get; }
-
-        ID TraceSegmentId { get; }
-
-        bool HasRef { get; }
-
-        bool IsIgnore { get; set; }
-
-        bool IsSingleSpanSegment { get; }
-
-        void Ref(ITraceSegmentRef refSegment);
-
-        void RelatedGlobalTrace(DistributedTraceId distributedTraceId);
-
-        SegmentRequest Transform();
-    }
-}

src/SkyWalking.Abstractions/Context/Trace/LogDataEntity.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using SkyWalking.Transport;
-
-namespace SkyWalking.Context.Trace
-{
-    public class LogDataEntity
-    {
-        private readonly long _timestamp;
-        private readonly Dictionary<string, string> _logs;
-
-        private LogDataEntity(long timestamp, Dictionary<string, string> logs)
-        {
-            _timestamp = timestamp;
-            _logs = logs;
-        }
-
-        public IReadOnlyDictionary<string, string> Logs => new ReadOnlyDictionary<string, string>(_logs);
-
-        public class Builder
-        {
-            private readonly Dictionary<string, string> _logs;
-
-            public Builder()
-            {
-                _logs = new Dictionary<string, string>();
-            }
-
-            public Builder Add(IDictionary<string, string> fields)
-            {
-                foreach (var field in fields)
-                    _logs.Add(field.Key, field.Value);
-                return this;
-            }
-
-            public Builder Add(string key, string value)
-            {
-                _logs.Add(key, value);
-                return this;
-            }
-
-            public LogDataEntity Build(long timestamp)
-            {
-                return new LogDataEntity(timestamp, _logs);
-            }
-        }
-
-        public LogDataRequest Transform()
-        {
-            var logMessage = new LogDataRequest();
-            logMessage.Timestamp = _timestamp;
-            foreach (var log in _logs)
-            {
-                logMessage.Data.Add(new KeyValuePair<string, string>(log.Key, log.Value));
-            }
-
-            return logMessage;
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Abstractions/Context/Trace/SpanLayer.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace SkyWalking.Context.Trace
-{
-    public enum SpanLayer
-    {
-        DB = 1,
-        RPC_FRAMEWORK = 2,
-        HTTP = 3,
-        MQ = 4,
-        CACHE = 5
-    }
-}

src/SkyWalking.Abstractions/Context/Trace/StackBasedTracingSpan.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-namespace SkyWalking.Context.Trace
-{
-    public abstract class StackBasedTracingSpan : AbstractTracingSpan
-    {
-        protected int _stackDepth;
-
-        protected StackBasedTracingSpan(int spanId, int parentSpanId, string operationName)
-            : base(spanId, parentSpanId, operationName)
-        {
-            _stackDepth = 0;
-        }
-
-        protected StackBasedTracingSpan(int spanId, int parentSpanId, int operationId)
-            : base(spanId, parentSpanId, operationId)
-        {
-            _stackDepth = 0;
-        }
-    }
-}

src/SkyWalking.Abstractions/Context/Trace/IWithPeerInfo.cs → src/SkyWalking.Abstractions/IBase64Formatter.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,12 +16,12 @@
  *
  */
 
-namespace SkyWalking.Context.Trace
+namespace SkyWalking
 {
-    public interface IWithPeerInfo
+    public interface IBase64Formatter
     {
-        int PeerId { get; }
+        string Decode(string value);
 
-        string Peer { get; }
+        string Encode(string value);
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/ISkyWalkingAgentStartup.cs → src/SkyWalking.Abstractions/IInstrumentStartup.cs

@@ -21,7 +21,7 @@ using System.Threading.Tasks;
 
 namespace SkyWalking
 {
-    public interface ISkyWalkingAgentStartup
+    public interface IInstrumentStartup
     {
         Task StartAsync(CancellationToken cancellationToken = default(CancellationToken));
 

src/SkyWalking.Abstractions/IRuntimeEnvironment.cs

@@ -17,6 +17,7 @@
  */
 
 using System;
+using SkyWalking.Common;
 
 namespace SkyWalking
 {

src/SkyWalking.Core/Context/Trace/NoopExitSpan.cs → src/SkyWalking.Abstractions/Tracing/Extensions/SegmentSpanExtensions.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -17,28 +17,27 @@
  */
 
 using System;
+using SkyWalking.Tracing.Segments;
 
-namespace SkyWalking.Context.Trace
+namespace SkyWalking.Tracing
 {
-    public class NoopExitSpan : NoopSpan, IWithPeerInfo
+    public static class SegmentSpanExtensions
     {
-        public int PeerId => peerId;
-
-        public string Peer => peer;
-
-        private String peer;
-        private int peerId;
-
-        public NoopExitSpan(int peerId)
+        public static void ErrorOccurred(this SegmentSpan span, Exception exception = null)
         {
-            this.peerId = peerId;
+            if (span == null)
+            {
+                return;
             }
 
-        public NoopExitSpan(String peer)
+            span.IsError = true;
+            if (exception != null)
             {
-            this.peer = peer;
+                span.AddLog(LogEvent.Event("error"), 
+                    LogEvent.ErrorKind(exception.GetType().FullName),
+                    LogEvent.Message(exception.Message), 
+                    LogEvent.ErrorStack(exception.StackTrace));
+            }
         }
-
-        public override bool IsExit { get; } = true;
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Context/Trace/ITraceSegmentRef.cs → src/SkyWalking.Abstractions/Tracing/ICarrier.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,19 +16,30 @@
  *
  */
 
-using System;
-using SkyWalking.Transport;
+using SkyWalking.Common;
 
-namespace SkyWalking.Context.Trace
+namespace SkyWalking.Tracing
 {
-    public interface ITraceSegmentRef : IEquatable<ITraceSegmentRef>
+    public interface ICarrier
     {
-        string EntryOperationName { get; }
+        bool HasValue { get; }
         
-        int EntryOperationId { get; }
+        bool? Sampled { get; }
 
-        int EntryApplicationInstanceId { get; }
+        UniqueId TraceId { get; }
 
-        SegmentReferenceRequest Transform();
+        UniqueId ParentSegmentId { get; }
+
+        int ParentSpanId { get; }
+
+        int ParentServiceInstanceId { get; }
+        
+        int EntryServiceInstanceId { get; }
+        
+        StringOrIntValue NetworkAddress { get; }
+        
+        StringOrIntValue EntryEndpoint { get; }
+        
+        StringOrIntValue ParentEndpoint { get; }
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Tracing/ICarrierFormatter.cs

+/*
+ * Licensed to the OpenSkywalking under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+using SkyWalking.Tracing.Segments;
+
+namespace SkyWalking.Tracing
+{
+    public interface ICarrierFormatter
+    {
+        string Key { get; }
+
+        bool Enable { get; }
+
+        ICarrier Decode(string content);
+
+        string Encode(ICarrier carrier);
+    }
+}
\ No newline at end of file

src/SkyWalking.Abstractions/Tracing/ICarrierHeaderCollection.cs

+using System.Collections.Generic;
+
+namespace SkyWalking.Tracing
+{
+    public interface ICarrierHeaderCollection : IEnumerable<KeyValuePair<string, string>>
+    {
+        void Add(string key, string value);
+    }
+}
\ No newline at end of file

src/SkyWalking.Abstractions/Context/Ids/IDistributedTraceIdCollection.cs → src/SkyWalking.Abstractions/Tracing/ICarrierPropagator.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,14 +16,14 @@
  *
  */
 
-using System.Collections.Generic;
+using SkyWalking.Tracing.Segments;
 
-namespace SkyWalking.Context.Ids
+namespace SkyWalking.Tracing
 {
-    public interface IDistributedTraceIdCollection
+    public interface ICarrierPropagator
     {
-        IReadOnlyList<DistributedTraceId> GetRelatedGlobalTraces();
+        void Inject(SegmentContext segmentContext, ICarrierHeaderCollection carrier);
 
-        void Append(DistributedTraceId distributedTraceId);
+        ICarrier Extract(ICarrierHeaderCollection carrier);
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Tracing/IEntrySegmentContextAccessor.cs

+/*
+ * Licensed to the OpenSkywalking under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+using SkyWalking.Tracing.Segments;
+
+namespace SkyWalking.Tracing
+{
+    public interface IEntrySegmentContextAccessor
+    {
+        SegmentContext Context { get; set; }
+    }
+}
\ No newline at end of file

src/SkyWalking.Abstractions/Context/IIgnoreTracerContextListener.cs → src/SkyWalking.Abstractions/Tracing/IExitSegmentContextAccessor.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,10 +16,12 @@
  *
  */
 
-namespace SkyWalking.Context
+using SkyWalking.Tracing.Segments;
+
+namespace SkyWalking.Tracing
 {
-    public interface IIgnoreTracerContextListener
+    public interface IExitSegmentContextAccessor
     {
-        void AfterFinish(ITracerContext tracerContext);
+        SegmentContext Context { get; set; }
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Tracing/ILocalSegmentContextAccessor.cs

+/*
+ * Licensed to the OpenSkywalking under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+using SkyWalking.Tracing.Segments;
+
+namespace SkyWalking.Tracing
+{
+    public interface ILocalSegmentContextAccessor
+    {
+        SegmentContext Context { get; set; }
+    }
+}
\ No newline at end of file

src/SkyWalking.Abstractions/ISampler.cs → src/SkyWalking.Abstractions/Tracing/ISamplerChainBuilder.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,12 +16,10 @@
  *
  */
 
-namespace SkyWalking
+namespace SkyWalking.Tracing
 {
-    public interface ISampler
+    public interface ISamplerChainBuilder
     {
-        bool Sampled();
-
-        void ForceSampled();
+        Sampler Build();
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Config/RuntimeConfig.cs → src/SkyWalking.Abstractions/Tracing/ISamplingInterceptor.cs

@@ -16,12 +16,14 @@
  *
  */
 
-namespace SkyWalking.Config
+using SkyWalking.Tracing.Segments;
+
+namespace SkyWalking.Tracing
 {
-    public class RuntimeConfig
+    public interface ISamplingInterceptor
     {
-        public NullableValue ApplicationId { get; set; }
+        int Priority { get; }
         
-        public NullableValue ApplicationInstance { get; set; }
+        bool Invoke(SamplingContext samplingContext, Sampler next);
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Components/IComponent.cs → src/SkyWalking.Abstractions/Tracing/ISegmentContextFactory.cs

@@ -16,15 +16,19 @@
  *
  */
 
-namespace SkyWalking.Components
+using SkyWalking.Common;
+using SkyWalking.Tracing.Segments;
+
+namespace SkyWalking.Tracing
 {
-    /// <summary>
-    /// The <code>Component</code> represents component library , which has been supported by skywalking
-    /// </summary>
-    public interface IComponent
+    public interface ISegmentContextFactory
     {
-        int Id { get; }
+        SegmentContext CreateEntrySegment(string operationName, ICarrier carrier);
+
+        SegmentContext CreateLocalSegment(string operationName);
+
+        SegmentContext CreateExitSegment(string operationName, StringOrIntValue networkAddress);
         
-        string Name { get; }
+        void Release(SegmentContext segmentContext);
     }
 }
\ No newline at end of file

src/SkyWalking.Core/Context/ContextCarrierFactory.cs → src/SkyWalking.Abstractions/Tracing/ITracingContext.cs

@@ -16,22 +16,19 @@
  *
  */
 
-using SkyWalking.Config;
+using SkyWalking.Tracing.Segments;
 
-namespace SkyWalking.Context
+namespace SkyWalking.Tracing
 {
-    public class ContextCarrierFactory : IContextCarrierFactory
+    public interface ITracingContext
     {
-        private readonly InstrumentationConfig _config;
+        SegmentContext CreateEntrySegmentContext(string operationName, ICarrierHeaderCollection carrierHeader);
 
-        public ContextCarrierFactory(IConfigAccessor configAccessor)
-        {
-            _config = configAccessor.Get<InstrumentationConfig>();
-        }
+        SegmentContext CreateLocalSegmentContext(string operationName);
 
-        public IContextCarrier Create()
-        {
-            return new ContextCarrier(_config.Namespace);
-        }
+        SegmentContext CreateExitSegmentContext(string operationName, string networkAddress,
+            ICarrierHeaderCollection carrierHeader = default(ICarrierHeaderCollection));
+
+        void Release(SegmentContext segmentContext);
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Context/Trace/SegmentRefType.cs → src/SkyWalking.Abstractions/Tracing/IUniqueIdGenerator.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,11 +16,10 @@
  *
  */
 
-namespace SkyWalking.Context.Trace
+namespace SkyWalking.Tracing
 {
-    public enum SegmentRefType
+    public interface IUniqueIdGenerator
     {
-        CrossProcess = 0,
-        CrossThread = 1
+        UniqueId Generate();
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Context/IContextCarrierFactory.cs → src/SkyWalking.Abstractions/Tracing/IUniqueIdParser.cs

@@ -16,10 +16,10 @@
  *
  */
 
-namespace SkyWalking.Context
+namespace SkyWalking.Tracing
 {
-    public interface IContextCarrierFactory
+    public interface IUniqueIdParser
     {
-        IContextCarrier Create();
+        bool TryParse(string text, out UniqueId uniqueId);
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Tracing/Sampler.cs

+/*
+ * Licensed to the OpenSkywalking under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+using SkyWalking.Common;
+using SkyWalking.Tracing.Segments;
+
+namespace SkyWalking.Tracing
+{
+    public delegate bool Sampler(SamplingContext samplingContext);
+
+    public class SamplingContext
+    {
+        public string OperationName { get; }
+
+        public StringOrIntValue Peer { get; }
+
+        public StringOrIntValue EntryEndpoint { get; }
+
+        public StringOrIntValue ParentEndpoint { get; }
+
+        public SamplingContext(string operationName, StringOrIntValue peer, StringOrIntValue entryEndpoint,
+            StringOrIntValue parentEndpoint)
+        {
+            OperationName = operationName;
+            Peer = peer;
+            EntryEndpoint = entryEndpoint;
+            ParentEndpoint = parentEndpoint;
+        }
+    }
+}
\ No newline at end of file

src/SkyWalking.Abstractions/Tracing/Segments/SegmentContext.cs

+/*
+ * Licensed to the OpenSkywalking under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+namespace SkyWalking.Tracing.Segments
+{
+    public class SegmentContext
+    {
+        public UniqueId SegmentId { get; }
+
+        public UniqueId TraceId { get; }
+
+        public SegmentSpan Span { get; }
+
+        public int ServiceId { get; }
+
+        public int ServiceInstanceId { get; }
+
+        public bool Sampled { get; }
+
+        public bool IsSizeLimited { get; } = false;
+
+        public SegmentReferenceCollection References { get; } = new SegmentReferenceCollection();
+
+        public SegmentContext(UniqueId traceId, UniqueId segmentId, bool sampled, int serviceId, int serviceInstanceId,
+            string operationName, SpanType spanType)
+        {
+            TraceId = traceId;
+            Sampled = sampled;
+            SegmentId = segmentId;
+            ServiceId = serviceId;
+            ServiceInstanceId = serviceInstanceId;
+            Span = new SegmentSpan(operationName, spanType);
+        }
+    }
+}
\ No newline at end of file

src/SkyWalking.Core/Context/Trace/NoopSpan.cs → src/SkyWalking.Abstractions/Tracing/Segments/SegmentReference.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,72 +16,56 @@
  *
  */
 
-using System;
+using System.Collections;
 using System.Collections.Generic;
-using SkyWalking.Components;
+using SkyWalking.Common;
 
-namespace SkyWalking.Context.Trace
+namespace SkyWalking.Tracing.Segments
 {
-    public class NoopSpan : ISpan
+    public class SegmentReference
     {
-        public int SpanId => 0;
+        public Reference Reference { get; set; }
 
-        public string OperationName { get => string.Empty; set { } }
+        public UniqueId ParentSegmentId { get; set; }
 
-        public int OperationId { get => 0; set { } }
+        public int ParentSpanId { get; set; }
 
-        public ISpan ErrorOccurred()
-        {
-            return this;
-        }
+        public int ParentServiceInstanceId { get; set; }
 
-        public ISpan Log(Exception exception)
-        {
-            return this;
-        }
+        public int EntryServiceInstanceId { get; set; }
 
-        public ISpan Log(long timestamp, IDictionary<string, object> @event)
-        {
-            return this;
-        }
+        public StringOrIntValue NetworkAddress { get; set; }
 
-        public void Ref(ITraceSegmentRef traceSegmentRef)
-        {
-        }
+        public StringOrIntValue EntryEndpoint { get; set; }
 
-        public ISpan SetComponent(IComponent component)
-        {
-            return this;
+        public StringOrIntValue ParentEndpoint { get; set; }
     }
 
-        public ISpan SetComponent(string componentName)
+    public enum Reference
     {
-            return this;
+        CrossProcess = 0,
+        CrossThread = 1
     }
 
-        public ISpan SetLayer(SpanLayer layer)
+    public class SegmentReferenceCollection : IEnumerable<SegmentReference>
     {
-            return this;
-        }
+        private readonly HashSet<SegmentReference> _references = new HashSet<SegmentReference>();
 
-        public ISpan Start()
+        public bool Add(SegmentReference reference)
         {
-            return this;
+            return _references.Add(reference);
         }
         
-        public ISpan Start(long timestamp)
+        public IEnumerator<SegmentReference> GetEnumerator()
         {
-            return this;
+            return _references.GetEnumerator();
         }
 
-        public ISpan Tag(string key, string value)
+        IEnumerator IEnumerable.GetEnumerator()
         {
-            return this;
+            return _references.GetEnumerator();
         }
 
-
-        public virtual bool IsEntry => false;
-
-        public virtual bool IsExit => false;
+        public int Count => _references.Count;
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Tracing/Segments/SegmentSpan.cs

+/*
+ * Licensed to the OpenSkywalking under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using SkyWalking.Common;
+
+namespace SkyWalking.Tracing.Segments
+{
+    public class SegmentSpan
+    {
+        public int SpanId { get; } = 0;
+
+        public int ParentSpanId { get; } = -1;
+
+        public long StartTime { get; } = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
+
+        public long EndTime { get; private set; }
+
+        public StringOrIntValue OperationName { get; }
+
+        public StringOrIntValue Peer { get; set; }
+
+        public SpanType SpanType { get; }
+
+        public SpanLayer SpanLayer { get; set; }
+
+        public StringOrIntValue Component { get; set; }
+
+        public bool IsError { get; set; }
+        public TagCollection Tags { get; } = new TagCollection();
+
+        public LogCollection Logs { get; } = new LogCollection();
+
+        public SegmentSpan(string operationName, SpanType spanType)
+        {
+            OperationName = new StringOrIntValue(operationName);
+            SpanType = spanType;
+        }
+
+        public SegmentSpan AddTag(string key, string value)
+        {
+            Tags.AddTag(key, value);
+            return this;
+        }
+
+        public SegmentSpan AddTag(string key, long value)
+        {
+            Tags.AddTag(key, value.ToString());
+            return this;
+        }
+
+        public SegmentSpan AddTag(string key, bool value)
+        {
+            Tags.AddTag(key, value.ToString());
+            return this;
+        }
+
+        public void AddLog(params LogEvent[] events)
+        {
+            var log = new SpanLog(DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(), events);
+            Logs.AddLog(log);
+        }
+
+        public void Finish()
+        {
+            EndTime = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
+        }
+    }
+
+    public class TagCollection : IEnumerable<KeyValuePair<string, string>>
+    {
+        private readonly Dictionary<string, string> tags = new Dictionary<string, string>();
+
+        internal void AddTag(string key, string value)
+        {
+            tags[key] = value;
+        }
+
+        public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
+        {
+            return tags.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return tags.GetEnumerator();
+        }
+    }
+
+    public enum SpanType
+    {
+        Entry = 0,
+        Exit = 1,
+        Local = 2
+    }
+
+    public enum SpanLayer
+    {
+        DB = 1,
+        RPC_FRAMEWORK = 2,
+        HTTP = 3,
+        MQ = 4,
+        CACHE = 5
+    }
+
+    public class LogCollection : IEnumerable<SpanLog>
+    {
+        private readonly List<SpanLog> _logs = new List<SpanLog>();
+
+        internal void AddLog(SpanLog log)
+        {
+            _logs.Add(log);
+        }
+
+        public IEnumerator<SpanLog> GetEnumerator()
+        {
+            return _logs.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return _logs.GetEnumerator();
+        }
+    }
+
+    public class SpanLog
+    {
+        private static readonly Dictionary<string, string> Empty = new Dictionary<string, string>();
+        public long Timestamp { get; }
+
+        public IReadOnlyDictionary<string, string> Data { get; }
+
+        public SpanLog(long timestamp, params LogEvent[] events)
+        {
+            Timestamp = timestamp;
+            Data = events?.ToDictionary(x => x.Key, x => x.Value) ?? Empty;
+        }
+    }
+
+    public class LogEvent
+    {
+        public string Key { get; }
+
+        public string Value { get; }
+
+        public LogEvent(string key, string value)
+        {
+            Key = key;
+            Value = value;
+        }
+
+        public static LogEvent Event(string value)
+        {
+            return new LogEvent("event", value);
+        }
+
+        public static LogEvent Message(string value)
+        {
+            return new LogEvent("message", value);
+        }
+
+        public static LogEvent ErrorKind(string value)
+        {
+            return new LogEvent("error.kind", value);
+        }
+
+        public static LogEvent ErrorStack(string value)
+        {
+            return new LogEvent("stack", value);
+        }
+    }
+}
\ No newline at end of file

src/SkyWalking.Abstractions/Tracing/UniqueId.cs

+/*
+ * Licensed to the OpenSkywalking under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+using System;
+
+namespace SkyWalking.Tracing
+{
+    public class UniqueId : IEquatable<UniqueId>
+    {
+        public long Part1 { get; }
+
+        public long Part2 { get; }
+
+        public long Part3 { get; }
+
+        public UniqueId(long part1, long part2, long part3)
+        {
+            Part1 = part1;
+            Part2 = part2;
+            Part3 = part3;
+        }
+
+        public override string ToString() => $"{Part1}.{Part2}.{Part3}";
+
+        public bool Equals(UniqueId other)
+        {
+            if (ReferenceEquals(null, other)) return false;
+            if (ReferenceEquals(this, other)) return true;
+            if (Part1 != other.Part1) return false;
+            if (Part2 != other.Part2) return false;
+            return Part3 == other.Part3;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            if (ReferenceEquals(this, obj)) return true;
+            if (!(obj is UniqueId id)) return false;
+            return Equals(id);
+        }
+
+        public override int GetHashCode()
+        {
+            throw new NotImplementedException();
+        }
+    }
+}
\ No newline at end of file

src/SkyWalking.Abstractions/Context/ITracingContextListener.cs → src/SkyWalking.Abstractions/Transport/ISegmentContextMapper.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,12 +16,12 @@
  *
  */
 
-using SkyWalking.Context.Trace;
+using SkyWalking.Tracing.Segments;
 
-namespace SkyWalking.Context
+namespace SkyWalking.Transport
 {
-   public interface ITracingContextListener
+    public interface ISegmentContextMapper
     {
-        void AfterFinished(ITraceSegment traceSegment);
+        SegmentRequest Map(SegmentContext segmentContext);
     }
 }
\ No newline at end of file

src/SkyWalking.Abstractions/Transport/ISegmentDispatcher.cs

@@ -18,12 +18,13 @@
 
 using System.Threading;
 using System.Threading.Tasks;
+using SkyWalking.Tracing.Segments;
 
 namespace SkyWalking.Transport
 {
     public interface ISegmentDispatcher
     {
-        bool Dispatch(SegmentRequest segment);
+        bool Dispatch(SegmentContext segmentContext);
 
         Task Flush(CancellationToken token = default(CancellationToken));
 

src/SkyWalking.Abstractions/Transport/IServiceRegister.cs

@@ -19,6 +19,7 @@
 using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
+using SkyWalking.Common;
 using SkyWalking.Transport;
 
 namespace SkyWalking.Transport

src/SkyWalking.Abstractions/Transport/SegmentRequest.cs

@@ -17,6 +17,7 @@
  */
 
 using System.Collections.Generic;
+using SkyWalking.Common;
 
 namespace SkyWalking.Transport
 {

src/SkyWalking.Abstractions/Transport/V5/ISkyWalkingClientV5.cs

@@ -19,6 +19,7 @@
 using System;
 using System.Threading;
 using System.Threading.Tasks;
+using SkyWalking.Common;
 
 namespace SkyWalking.Transport
 {

src/SkyWalking.Agent.AspNetCore/Extensions/ServiceCollectionExtensions.cs

@@ -21,7 +21,6 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using SkyWalking.AspNetCore.Diagnostics;
 using SkyWalking.Config;
-using SkyWalking.Context;
 using SkyWalking.Diagnostics;
 using SkyWalking.Diagnostics.EntityFrameworkCore;
 using SkyWalking.Diagnostics.HttpClient;
@@ -30,7 +29,9 @@ using SkyWalking.Utilities.Configuration;
 using SkyWalking.Utilities.DependencyInjection;
 using SkyWalking.Utilities.Logging;
 using SkyWalking.Logging;
+using SkyWalking.Sampling;
 using SkyWalking.Service;
+using SkyWalking.Tracing;
 using SkyWalking.Transport;
 using SkyWalking.Transport.Grpc;
 using SkyWalking.Transport.Grpc.V5;
@@ -47,26 +48,50 @@ namespace SkyWalking.Agent.AspNetCore
                 throw new ArgumentNullException(nameof(services));
             }
             
-            services.AddSingleton<IContextCarrierFactory, ContextCarrierFactory>();
             services.AddSingleton<ISegmentDispatcher, AsyncQueueSegmentDispatcher>();
-            services.AddSingleton<IExecutionService, SegmentReportService>();
             services.AddSingleton<IExecutionService, RegisterService>();
             services.AddSingleton<IExecutionService, PingService>();
-            services.AddSingleton<IExecutionService, SamplingRefreshService>();
             services.AddSingleton<IExecutionService, ServiceDiscoveryV5Service>();
-            services.AddSingleton<ISkyWalkingAgentStartup, SkyWalkingAgentStartup>();
-            services.AddSingleton<ISampler>(DefaultSampler.Instance);
+            services.AddSingleton<IExecutionService, SegmentReportService>();
+            services.AddSingleton<IInstrumentStartup, InstrumentStartup>();
             services.AddSingleton<IRuntimeEnvironment>(RuntimeEnvironment.Instance);
             services.AddSingleton<TracingDiagnosticProcessorObserver>();
             services.AddSingleton<IConfigAccessor, ConfigAccessor>();
             services.AddSingleton<IHostedService, InstrumentationHostedService>();
             services.AddSingleton<IEnvironmentProvider, HostingEnvironmentProvider>();
-            services.AddGrpcTransport().AddLogging();
+            services.AddTracing().AddSampling().AddGrpcTransport().AddLogging();
             services.AddSkyWalkingExtensions().AddAspNetCoreHosting().AddHttpClient().AddSqlClient()
                 .AddEntityFrameworkCore(c => c.AddPomeloMysql().AddNpgsql().AddSqlite());
             return services;
         }
 
+        private static IServiceCollection AddTracing(this IServiceCollection services)
+        {
+            services.AddSingleton<ITracingContext, Tracing.TracingContext>();
+            services.AddSingleton<ICarrierPropagator, CarrierPropagator>();
+            services.AddSingleton<ICarrierFormatter, Sw3CarrierFormatter>();
+            services.AddSingleton<ICarrierFormatter, Sw6CarrierFormatter>();
+            services.AddSingleton<ISegmentContextFactory, SegmentContextFactory>();
+            services.AddSingleton<IEntrySegmentContextAccessor, EntrySegmentContextAccessor>();
+            services.AddSingleton<ILocalSegmentContextAccessor, LocalSegmentContextAccessor>();
+            services.AddSingleton<IExitSegmentContextAccessor, ExitSegmentContextAccessor>();
+            services.AddSingleton<ISamplerChainBuilder, SamplerChainBuilder>();
+            services.AddSingleton<IUniqueIdGenerator, UniqueIdGenerator>();
+            services.AddSingleton<IUniqueIdParser, UniqueIdParser>();
+            services.AddSingleton<ISegmentContextMapper, SegmentContextMapper>();
+            services.AddSingleton<IBase64Formatter, Base64Formatter>();
+            return services;
+        }
+
+        private static IServiceCollection AddSampling(this IServiceCollection services)
+        {
+            services.AddSingleton<SimpleCountSamplingInterceptor>();
+            services.AddSingleton<ISamplingInterceptor>(p => p.GetService<SimpleCountSamplingInterceptor>());
+            services.AddSingleton<IExecutionService>(p => p.GetService<SimpleCountSamplingInterceptor>());
+            services.AddSingleton<ISamplingInterceptor, RandomSamplingInterceptor>();
+            return services;
+        }
+
         private static IServiceCollection AddGrpcTransport(this IServiceCollection services)
         {
             services.AddSingleton<ISkyWalkingClientV5, SkyWalkingClientV5>();

src/SkyWalking.Agent.AspNetCore/InstrumentationHostedService.cs

@@ -24,9 +24,9 @@ namespace SkyWalking.Agent.AspNetCore
 {
     internal class InstrumentationHostedService : IHostedService
     {
-        private readonly ISkyWalkingAgentStartup _startup;
+        private readonly IInstrumentStartup _startup;
 
-        public InstrumentationHostedService(ISkyWalkingAgentStartup startup)
+        public InstrumentationHostedService(IInstrumentStartup startup)
         {
             _startup = startup;
         }

src/SkyWalking.AspNet/Extensions/ServiceCollectionExtensions.cs

@@ -18,10 +18,11 @@
 
 using Microsoft.Extensions.DependencyInjection;
 using SkyWalking.Config;
-using SkyWalking.Context;
 using SkyWalking.Diagnostics;
 using SkyWalking.Logging;
+using SkyWalking.Sampling;
 using SkyWalking.Service;
+using SkyWalking.Tracing;
 using SkyWalking.Transport;
 using SkyWalking.Transport.Grpc;
 using SkyWalking.Transport.Grpc.V5;
@@ -35,26 +36,45 @@ namespace SkyWalking.AspNet.Extensions
     {
         public static IServiceCollection AddSkyWalkingCore(this IServiceCollection services)
         {
-            services.AddSingleton<IContextCarrierFactory, ContextCarrierFactory>();
             services.AddSingleton<ISegmentDispatcher, AsyncQueueSegmentDispatcher>();
-            services.AddSingleton<IExecutionService, SegmentReportService>();
             services.AddSingleton<IExecutionService, RegisterService>();
             services.AddSingleton<IExecutionService, PingService>();
-            services.AddSingleton<IExecutionService, SamplingRefreshService>();
             services.AddSingleton<IExecutionService, ServiceDiscoveryV5Service>();
-            services.AddSingleton<ISkyWalkingAgentStartup, SkyWalkingAgentStartup>();
-            services.AddSingleton<ISampler>(DefaultSampler.Instance);
+            services.AddSingleton<IExecutionService, SegmentReportService>();
+            services.AddSingleton<IInstrumentStartup, InstrumentStartup>();
             services.AddSingleton<IRuntimeEnvironment>(RuntimeEnvironment.Instance);
             services.AddSingleton<TracingDiagnosticProcessorObserver>();
             services.AddSingleton<IConfigAccessor, ConfigAccessor>();
             services.AddSingleton<IEnvironmentProvider, HostingEnvironmentProvider>();
+            services.AddSingleton<InstrumentRequestCallback>();
+            
+            services.AddSingleton<ITracingContext, Tracing.TracingContext>();
+            services.AddSingleton<ICarrierPropagator, CarrierPropagator>();
+            services.AddSingleton<ICarrierFormatter, Sw3CarrierFormatter>();
+            services.AddSingleton<ICarrierFormatter, Sw6CarrierFormatter>();
+            services.AddSingleton<ISegmentContextFactory, SegmentContextFactory>();
+            services.AddSingleton<IEntrySegmentContextAccessor, EntrySegmentContextAccessor>();
+            services.AddSingleton<ILocalSegmentContextAccessor, LocalSegmentContextAccessor>();
+            services.AddSingleton<IExitSegmentContextAccessor, ExitSegmentContextAccessor>();
+            services.AddSingleton<ISamplerChainBuilder, SamplerChainBuilder>();
+            services.AddSingleton<IUniqueIdGenerator, UniqueIdGenerator>();
+            services.AddSingleton<IUniqueIdParser, UniqueIdParser>();
+            services.AddSingleton<ISegmentContextMapper, SegmentContextMapper>();
+            services.AddSingleton<IBase64Formatter, Base64Formatter>();
+            
+            services.AddSingleton<SimpleCountSamplingInterceptor>();
+            services.AddSingleton<ISamplingInterceptor>(p => p.GetService<SimpleCountSamplingInterceptor>());
+            services.AddSingleton<IExecutionService>(p => p.GetService<SimpleCountSamplingInterceptor>());
+            services.AddSingleton<ISamplingInterceptor, RandomSamplingInterceptor>();
+            
+            services.AddSingleton<ISkyWalkingClientV5, SkyWalkingClientV5>();
             services.AddSingleton<ISegmentReporter, SegmentReporter>();
             services.AddSingleton<ConnectionManager>();
             services.AddSingleton<IPingCaller, PingCaller>();
             services.AddSingleton<IServiceRegister, ServiceRegister>();
             services.AddSingleton<IExecutionService, ConnectService>();
+            
             services.AddSingleton<ILoggerFactory, DefaultLoggerFactory>();
-            services.AddSingleton<ISkyWalkingClientV5, SkyWalkingClientV5>();
             return services;
         }
     }

src/SkyWalking.Core/Context/Ids/DistributedTraceIdCollection.cs → src/SkyWalking.AspNet/HttpRequestCarrierHeaderCollection.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,34 +16,39 @@
  *
  */
 
+using System.Collections;
 using System.Collections.Generic;
+using System.Web;
+using SkyWalking.Tracing;
 
-namespace SkyWalking.Context.Ids
+namespace SkyWalking.AspNet
 {
-    public class DistributedTraceIdCollection : IDistributedTraceIdCollection
+    public class HttpRequestCarrierHeaderCollection : ICarrierHeaderCollection
     {
-        private readonly List<DistributedTraceId> _relatedGlobalTraces;
+        private readonly Dictionary<string, string> _headers;
 
-        public DistributedTraceIdCollection()
+        public HttpRequestCarrierHeaderCollection(HttpRequest httpRequest)
         {
-            _relatedGlobalTraces = new List<DistributedTraceId>();
+            _headers = new Dictionary<string, string>();
+            foreach (var key in httpRequest.Headers.AllKeys)
+            {
+                _headers[key] = httpRequest.Headers[key];
+            }
         }
 
-        public IReadOnlyList<DistributedTraceId> GetRelatedGlobalTraces()
+        public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
         {
-            return _relatedGlobalTraces.AsReadOnly();
+            return _headers.GetEnumerator();
         }
 
-        public void Append(DistributedTraceId distributedTraceId)
-        {
-            if (_relatedGlobalTraces.Count > 0 && _relatedGlobalTraces[0] is NewDistributedTraceId)
+        IEnumerator IEnumerable.GetEnumerator()
         {
-                _relatedGlobalTraces.RemoveAt(0);
+            return _headers.GetEnumerator();
         }
-            if (!_relatedGlobalTraces.Contains(distributedTraceId))
+
+        public void Add(string key, string value)
         {
-                _relatedGlobalTraces.Add(distributedTraceId);
-            }
+            throw new System.NotImplementedException();
         }
     }
 }
\ No newline at end of file

src/SkyWalking.AspNet/HttpTracingHandler.cs

@@ -17,74 +17,88 @@
  */
 
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Net.Http;
+using System.Net.Http.Headers;
 using System.Threading;
 using System.Threading.Tasks;
-using SkyWalking.Components;
-using SkyWalking.Context;
-using SkyWalking.Context.Tag;
-using SkyWalking.Context.Trace;
+using CommonServiceLocator;
+using SkyWalking.Tracing;
+using SpanLayer = SkyWalking.Tracing.Segments.SpanLayer;
 
 namespace SkyWalking.AspNet
 {
     public class HttpTracingHandler : DelegatingHandler
     {
-        private readonly IContextCarrierFactory _contextCarrierFactory;
-
         public HttpTracingHandler()
             : this(new HttpClientHandler())
         {
         }
 
         public HttpTracingHandler(HttpMessageHandler innerHandler)
-            : this(innerHandler, CommonServiceLocator.ServiceLocator.Current.GetInstance<IContextCarrierFactory>())
-        {
-        }
-
-        private HttpTracingHandler(HttpMessageHandler innerHandler, IContextCarrierFactory contextCarrierFactory)
         {
             InnerHandler = innerHandler;
-            _contextCarrierFactory = contextCarrierFactory;
         }
 
         protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,
             CancellationToken cancellationToken)
         {
-            var peer = $"{request.RequestUri.Host}:{request.RequestUri.Port}";
-            var contextCarrier = _contextCarrierFactory.Create();
-            var span = ContextManager.CreateExitSpan(request.RequestUri.ToString(), contextCarrier, peer);
+            var tracingContext = ServiceLocator.Current.GetInstance<ITracingContext>();
+            var operationName = request.RequestUri.ToString();
+            var networkAddress = $"{request.RequestUri.Host}:{request.RequestUri.Port}";
+            var context = tracingContext.CreateExitSegmentContext(operationName, networkAddress,
+                new CarrierHeaderCollection(request.Headers));
             try
             {
-                Tags.Url.Set(span, request.RequestUri.ToString());
-                span.AsHttp();
-                span.SetComponent(ComponentsDefine.HttpClient);
-                Tags.HTTP.Method.Set(span, request.Method.ToString());
-                foreach (var item in contextCarrier.Items)
-                    request.Headers.Add(item.HeadKey, item.HeadValue);
-
-                if (request.Method.Method != "GET")
-                {
-                    // record request body data
-                    if (!request.Content.Headers.ContentType?.MediaType.ToLower().Contains("multipart/form-data")??false)
+                context.Span.SpanLayer = SpanLayer.HTTP;
+                context.Span.Component = Common.Components.HTTPCLIENT;
+                context.Span.AddTag(Common.Tags.URL, request.RequestUri.ToString());
+                context.Span.AddTag(Common.Tags.PATH, request.RequestUri.PathAndQuery);
+                context.Span.AddTag(Common.Tags.HTTP_METHOD, request.Method.ToString());
+                var response = await base.SendAsync(request, cancellationToken);
+                var statusCode = (int) response.StatusCode;
+                if (statusCode >= 400)
                 {
-                        string bodyStr = await request.Content.ReadAsStringAsync();
-                        span.Log(DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(), new Dictionary<string, object> { { "Body", bodyStr } });
-                    }
+                    context.Span.ErrorOccurred();
                 }
 
-                var response = await base.SendAsync(request, cancellationToken);
-                Tags.StatusCode.Set(span, response.StatusCode.ToString());
+                context.Span.AddTag(Common.Tags.STATUS_CODE, statusCode);
                 return response;
             }
-            catch (Exception e)
+            catch (Exception exception)
             {
-                span.ErrorOccurred().Log(e);
+                context.Span.ErrorOccurred(exception);
                 throw;
             }
             finally
             {
-                ContextManager.StopSpan(span);
+                tracingContext.Release(context);
+            }
+        }
+
+        private class CarrierHeaderCollection : ICarrierHeaderCollection
+        {
+            private readonly HttpRequestHeaders _headers;
+
+            public CarrierHeaderCollection(HttpRequestHeaders headers)
+            {
+                _headers = headers;
+            }
+
+            public void Add(string key, string value)
+            {
+                _headers.Add(key, value);
+            }
+
+            public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
+            {
+                throw new NotImplementedException();
+            }
+
+            IEnumerator IEnumerable.GetEnumerator()
+            {
+                return GetEnumerator();
             }
         }
     }

src/SkyWalking.AspNet/SkyWalkingModule.cs → src/SkyWalking.AspNet/InstrumentModule.cs

@@ -19,13 +19,14 @@
 using CommonServiceLocator;
 using Microsoft.Extensions.DependencyInjection;
 using System.Web;
+using Nito.AsyncEx;
 using SkyWalking.AspNet.Extensions;
 
 namespace SkyWalking.AspNet
 {
-    public class SkyWalkingModule : IHttpModule
+    public class InstrumentModule : IHttpModule
     {
-        public SkyWalkingModule()
+        public InstrumentModule()
         {
             var serviceProvider = new ServiceCollection().AddSkyWalkingCore().BuildServiceProvider();
             var serviceLocatorProvider = new ServiceProviderLocator(serviceProvider);
@@ -34,15 +35,17 @@ namespace SkyWalking.AspNet
 
         public void Init(HttpApplication application)
         {
-            var startup = ServiceLocator.Current.GetInstance<ISkyWalkingAgentStartup>();
+            var startup = ServiceLocator.Current.GetInstance<IInstrumentStartup>();
             AsyncContext.Run(() => startup.StartAsync());
-            var requestCallback = ServiceLocator.Current.GetInstance<SkyWalkingApplicationRequestCallback>();
+            var requestCallback = ServiceLocator.Current.GetInstance<InstrumentRequestCallback>();
             application.BeginRequest += requestCallback.ApplicationOnBeginRequest;
             application.EndRequest += requestCallback.ApplicationOnEndRequest;
         }
 
         public void Dispose()
         {
+            var startup = ServiceLocator.Current.GetInstance<IInstrumentStartup>();
+            AsyncContext.Run(() => startup.StopAsync());
         }
     }
 }
\ No newline at end of file

src/SkyWalking.AspNet/SkyWalkingModuleRegister.cs → src/SkyWalking.AspNet/InstrumentModuleFactory.cs

@@ -20,15 +20,15 @@ using Microsoft.Web.Infrastructure.DynamicModuleHelper;
 using System.Web;
 using SkyWalking.AspNet;
 
-[assembly:PreApplicationStartMethod(typeof(SkyWalkingModuleRegister), "Register")]
+[assembly:PreApplicationStartMethod(typeof(InstrumentModuleFactory), nameof(InstrumentModuleFactory.Create))]
 
 namespace SkyWalking.AspNet
 {
-    public class SkyWalkingModuleRegister
+    public class InstrumentModuleFactory
     {
-        public static void Register()
+        public static void Create()
         {
-            DynamicModuleUtility.RegisterModule(typeof(SkyWalkingModule));
+            DynamicModuleUtility.RegisterModule(typeof(InstrumentModule));
         }
     }
 }
\ No newline at end of file

src/SkyWalking.AspNet/SkyWalkingApplicationRequestCallback.cs → src/SkyWalking.AspNet/InstrumentRequestCallback.cs

@@ -17,26 +17,27 @@
  */
 
 using System;
-using System.Collections.Generic;
-using System.IO;
 using System.Web;
-using SkyWalking.Components;
+using SkyWalking.Common;
 using SkyWalking.Config;
-using SkyWalking.Context;
-using SkyWalking.Context.Tag;
-using SkyWalking.Context.Trace;
+using SkyWalking.Tracing;
+using SkyWalking.Tracing.Segments;
+using SpanLayer = SkyWalking.Tracing.Segments.SpanLayer;
 
 namespace SkyWalking.AspNet
 {
-    internal class SkyWalkingApplicationRequestCallback
+    internal class InstrumentRequestCallback
     {
-        private readonly IContextCarrierFactory _contextCarrierFactory;
-        private readonly InstrumentationConfig _config;
+        private readonly InstrumentConfig _config;
+        private readonly ITracingContext _tracingContext;
+        private readonly IEntrySegmentContextAccessor _contextAccessor;
 
-        public SkyWalkingApplicationRequestCallback(IConfigAccessor configAccessor, IContextCarrierFactory carrierFactory)
+        public InstrumentRequestCallback(IConfigAccessor configAccessor, ITracingContext tracingContext,
+            IEntrySegmentContextAccessor contextAccessor)
         {
-            _config = configAccessor.Get<InstrumentationConfig>();
-            _contextCarrierFactory = carrierFactory;
+            _config = configAccessor.Get<InstrumentConfig>();
+            _tracingContext = tracingContext;
+            _contextAccessor = contextAccessor;
         }
 
         public void ApplicationOnBeginRequest(object sender, EventArgs e)
@@ -44,113 +45,57 @@ namespace SkyWalking.AspNet
             var httpApplication = sender as HttpApplication;
             var httpContext = httpApplication.Context;
 
-            if(httpContext.Request.HttpMethod == "OPTIONS")
+            if (httpContext.Request.HttpMethod == "OPTIONS")
             {
                 //asp.net Exclude OPTIONS request
                 return;
             }
-
-            var carrier = _contextCarrierFactory.Create();
-            foreach (var item in carrier.Items)
-                item.HeadValue = httpContext.Request.Headers[item.HeadKey];
-            var httpRequestSpan = ContextManager.CreateEntrySpan($"{_config.ApplicationCode} {httpContext.Request.Path}", carrier);
-            httpRequestSpan.AsHttp();
-            httpRequestSpan.SetComponent(ComponentsDefine.AspNet);
-            Tags.Url.Set(httpRequestSpan, httpContext.Request.Path);
-            Tags.HTTP.Method.Set(httpRequestSpan, httpContext.Request.HttpMethod);
-
-            var dictLog = new Dictionary<string, object>
-                {
-                    {"event", "AspNet BeginRequest"},
-                    {"message", $"Request starting {httpContext.Request.Url.Scheme} {httpContext.Request.HttpMethod} {httpContext.Request.Url.OriginalString}"}
-                };
-
-            // record request body data
-            SetBodyData(httpContext.Request, dictLog);
-            httpRequestSpan.Log(DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(), dictLog);
-
-            httpContext.Items.Add("span_Context", ContextManager.ActiveContext);
+            var context = _tracingContext.CreateEntrySegmentContext(httpContext.Request.Path,
+                new HttpRequestCarrierHeaderCollection(httpContext.Request));
+            context.Span.SpanLayer = SpanLayer.HTTP;
+            context.Span.Peer = new StringOrIntValue(httpContext.Request.UserHostAddress);
+            context.Span.Component = Common.Components.ASPNET;
+            context.Span.AddTag(Tags.URL, httpContext.Request.Url.OriginalString);
+            context.Span.AddTag(Tags.PATH, httpContext.Request.Path);
+            context.Span.AddTag(Tags.HTTP_METHOD, httpContext.Request.HttpMethod);
+            context.Span.AddLog(LogEvent.Event("AspNet BeginRequest"),
+                LogEvent.Message(
+                    $"Request starting {httpContext.Request.Url.Scheme} {httpContext.Request.HttpMethod} {httpContext.Request.Url.OriginalString}"));
         }
 
         public void ApplicationOnEndRequest(object sender, EventArgs e)
         {
-            var httpApplication = sender as HttpApplication;
-            var httpContext = httpApplication.Context;
-            ITracerContext context=null;
-
-            if (httpContext.Request.HttpMethod == "OPTIONS")
+            var context = _contextAccessor.Context;
+            if (context == null)
             {
-                //asp.net Exclude OPTIONS request
                 return;
             }
             
-            var httpRequestSpan = ContextManager.ActiveSpan;
-            if (httpRequestSpan == null)
+            var httpApplication = sender as HttpApplication;
+            var httpContext = httpApplication.Context;
+            if (httpContext.Request.HttpMethod == "OPTIONS")
             {
-                // ContextManager.ActiveSpan is null, from httpContext.Items
-                if(!httpContext.Items.Contains("span_Context"))
-                    return;
-
-                context = httpContext.Items["span_Context"] as ITracerContext;
-                if (context == null)
-                    return;
-
-                httpRequestSpan = context.ActiveSpan;
-                if (httpRequestSpan == null)
+                //asp.net Exclude OPTIONS request
                 return;
             }
             
             var statusCode = httpContext.Response.StatusCode;
             if (statusCode >= 400)
             {
-                httpRequestSpan.ErrorOccurred();
+                context.Span.ErrorOccurred();
             }
             
-            Tags.StatusCode.Set(httpRequestSpan, statusCode.ToString());
-
             var exception = httpContext.Error;
             if (exception != null)
             {
-                httpRequestSpan.ErrorOccurred().Log(exception);
-            }
-
-            httpRequestSpan.Log(DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
-                new Dictionary<string, object>
-                {
-                    {"event", "AspNet EndRequest"},
-                    {"message", $"Request finished {httpContext.Response.StatusCode} {httpContext.Response.ContentType}"}
-                });
-            
-            ContextManager.StopSpan(httpRequestSpan, context);
-        }
-
-        /// <summary>
-        /// record request body data
-        /// </summary>
-        /// <param name="request"></param>
-        /// <param name="dict"></param>
-        private void SetBodyData(HttpRequest request, Dictionary<string, object> dict)
-        {
-            if (request.HttpMethod == "GET")
-            {
-                return;
+                context.Span.ErrorOccurred(exception);
             }
 
-            if (dict == null)
-                dict = new Dictionary<string, object>();
+            context.Span.AddLog(LogEvent.Event("AspNet EndRequest"),
+                LogEvent.Message(
+                    $"Request finished {httpContext.Response.StatusCode} {httpContext.Response.ContentType}"));
             
-            if (request.ContentType?.ToLower().Contains("multipart/form-data")??false)
-            {
-                dict.Add("ContentLength", request.ContentLength);
-                return;
-            }
-
-            var stearm = request.GetBufferedInputStream();
-            using (StreamReader sr = new StreamReader(stearm))
-            {
-                var bodyStr = sr.ReadToEnd();
-                dict.Add("Body", bodyStr);
-            }
+            _tracingContext.Release(context);
         }
     }
 }
\ No newline at end of file

src/SkyWalking.AspNet/SkyWalking.AspNet.csproj

@@ -28,5 +28,6 @@
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="2.2.0" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="2.2.0" />
     <PackageReference Include="Microsoft.Web.Infrastructure" Version="1.0.0" />
+    <PackageReference Include="Nito.AsyncEx.Context" Version="1.1.0" />
   </ItemGroup>
 </Project>
\ No newline at end of file

src/SkyWalking.Core/Context/Tag/StringTag.cs → src/SkyWalking.Core/Base64Formatter.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -16,19 +16,21 @@
  *
  */
 
-using SkyWalking.Context.Trace;
+using System;
+using System.Text;
 
-namespace SkyWalking.Context.Tag
+namespace SkyWalking
 {
-    public class StringTag : AbstractTag<string>
+    public class Base64Formatter : IBase64Formatter
     {
-        public StringTag(string tagKey) : base(tagKey)
+        public string Decode(string value)
         {
+            return value == null ? value : Encoding.UTF8.GetString(Convert.FromBase64String(value));
         }
 
-        public override void Set(ISpan span, string tagValue)
+        public string Encode(string value)
         {
-            span.Tag(Key, tagValue);
+            return value == null ? value : Convert.ToBase64String(Encoding.UTF8.GetBytes(value));
         }
     }
 }
\ No newline at end of file

src/SkyWalking.Core/Utils/AtomicInteger.cs → src/SkyWalking.Core/Common/AtomicInteger.cs

@@ -2,7 +2,7 @@
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
@@ -18,7 +18,7 @@
 
 using System.Threading;
 
-namespace SkyWalking.Utils
+namespace SkyWalking.Common
 {
     public class AtomicInteger
     {

src/SkyWalking.Core/Utils/DnsHelpers.cs → src/SkyWalking.Core/Common/DnsHelpers.cs

@@ -2,7 +2,7 @@
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
@@ -20,7 +20,7 @@ using System.Linq;
 using System.Net;
 using System.Net.Sockets;
 
-namespace SkyWalking.Utils
+namespace SkyWalking.Common
 {
     public static class DnsHelpers
     {

src/SkyWalking.Core/Utils/EnumerableExtensions.cs → src/SkyWalking.Core/Common/EnumerableExtensions.cs

@@ -2,7 +2,7 @@
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
@@ -19,7 +19,7 @@
 using System;
 using System.Collections.Generic;
 
-namespace SkyWalking.Utils
+namespace SkyWalking.Common
 {
     internal static class EnumerableExtensions
     {

src/SkyWalking.AspNet/AsyncContext.cs → src/SkyWalking.Core/Common/PlatformInformation.cs

@@ -16,36 +16,32 @@
  *
  */
 
-using System;
-using System.Threading;
-using System.Threading.Tasks;
+using System.Runtime.InteropServices;
 
-namespace SkyWalking.AspNet
+namespace SkyWalking.Common
 {
-    internal static class AsyncContext
+    internal static class PlatformInformation
     {
-        public static void Run(Func<Task> task)
+        private const string OSX = "Mac OS X";
+        private const string LINUX = "Linux";
+        private const string WINDOWS = "Windows";
+
+        public static string GetOSName()
         {
-            using (new ContextScope())
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             {
-                Task.Run(async () => await task()).GetAwaiter().GetResult();
-            }
+                return WINDOWS;
             }
-
-        private class ContextScope : IDisposable
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
             {
-            private readonly SynchronizationContext _current;
-
-            public ContextScope()
-            {
-                _current = SynchronizationContext.Current;
-                SynchronizationContext.SetSynchronizationContext(null);
+                return LINUX;
             }
-
-            public void Dispose()
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
             {
-                SynchronizationContext.SetSynchronizationContext(_current);
+                return OSX;
             }
+
+            return "Unknown";
         }
     }
 }

src/SkyWalking.Core/Utils/StackExtensions.cs → src/SkyWalking.Core/Common/StackExtensions.cs

@@ -2,7 +2,7 @@
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
@@ -18,7 +18,7 @@
 
 using System.Collections.Generic;
 
-namespace SkyWalking.Utils
+namespace SkyWalking.Common
 {
     public static class StackExtensions
     {

src/SkyWalking.Abstractions/Components/OfficialComponent.cs → src/SkyWalking.Core/Common/StringOrIntValueHelpers.cs

@@ -16,18 +16,15 @@
  *
  */
 
-namespace SkyWalking.Components
+using System;
+
+namespace SkyWalking.Common
 {
-    public class OfficialComponent : IComponent
+    public static class StringOrIntValueHelpers
     {
-        public OfficialComponent(int id, string name)
+        public static StringOrIntValue ParseStringOrIntValue(string value)
         {
-            Id = id;
-            Name = name;
+            return value.StartsWith("#") ? new StringOrIntValue(new string(value.AsSpan().Slice(1, value.Length - 1).ToArray())) : new StringOrIntValue(int.Parse(value));
         }
-
-        public int Id { get; }
-
-        public string Name { get; }
     }
 }
\ No newline at end of file

src/SkyWalking.Core/Context/CarrierItemHead.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-
-namespace SkyWalking.Context
-{
-    public class CarrierItemHead : CarrierItem
-    {
-        public CarrierItemHead(CarrierItem next, string @namespace) : base(string.Empty, string.Empty, next, @namespace)
-        {
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/ContextCarrier.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Collections.Generic;
-using System.Linq;
-using SkyWalking.Context.Ids;
-
-namespace SkyWalking.Context
-{
-    public class ContextCarrier : IContextCarrier
-    {
-        private ID _traceSegmentId;
-
-        /// <summary>
-        /// id of parent span
-        /// </summary>
-        private int _spanId = -1;
-
-        /// <summary>
-        /// id of parent application instance
-        /// </summary>
-        private int _parentApplicationInstanceId = 0;
-
-        /// <summary>
-        /// id of first application instance in this distributed trace
-        /// </summary>
-        private int _entryApplicationInstanceId = 0;
-
-        /// <summary>
-        /// peer(ipv4/ipv6/hostname + port) of the server , from client side .
-        /// </summary>
-        private string _peerHost;
-
-        private int _peerId;
-
-        /// <summary>
-        /// Operation/Service name of the first one in this distributed trace .
-        /// </summary>
-        private string _entryOperationName;
-
-        private int _entryOperationId;
-
-        /// <summary>
-        /// Operation/Service name of the parent one in this distributed trace .
-        /// </summary>
-        private string _parentOperationName;
-
-        private int _parentOperationId;
-
-        private DistributedTraceId _primaryDistributedTraceId;
-
-        private readonly string _namespace;
-
-        public ContextCarrier(string @namespace)
-        {
-            _namespace = @namespace;
-        }
-
-        public DistributedTraceId DistributedTraceId => _primaryDistributedTraceId;
-
-        public int EntryApplicationInstanceId
-        {
-            get => _entryApplicationInstanceId;
-            set => _entryApplicationInstanceId = value;
-        }
-
-        public string EntryOperationName
-        {
-            get => _entryOperationName;
-            set => _entryOperationName = "#" + value;
-        }
-
-        public int EntryOperationId
-        {
-            get => _entryOperationId;
-            set => _entryOperationId = value;
-        }
-
-        public int ParentApplicationInstanceId
-        {
-            get => _parentApplicationInstanceId;
-            set => _parentApplicationInstanceId = value;
-        }
-
-        public string ParentOperationName
-        {
-            get => _parentOperationName;
-            set => _parentOperationName = "#" + value;
-        }
-
-        public int ParentOperationId
-        {
-            get => _parentOperationId;
-            set => _parentOperationId = value;
-        }
-
-        public string PeerHost
-        {
-            get => _peerHost;
-            set => _peerHost = "#" + value;
-        }
-
-        public int PeerId
-        {
-            get => _peerId;
-            set => _peerId = value;
-        }
-
-        public int SpanId
-        {
-            get => _spanId;
-            set => _spanId = value;
-        }
-
-        public ID TraceSegmentId
-        {
-            get => _traceSegmentId;
-            set => _traceSegmentId = value;
-        }
-
-        public bool IsValid
-        {
-            get
-            {
-                return _traceSegmentId != null
-                       && _traceSegmentId.IsValid
-                       && _spanId > -1
-                       && _parentApplicationInstanceId != 0
-                       && _entryApplicationInstanceId != 0
-                       && !string.IsNullOrEmpty(_peerHost)
-                       && !string.IsNullOrEmpty(_parentOperationName)
-                       && !string.IsNullOrEmpty(_entryOperationName)
-                       && _primaryDistributedTraceId != null;
-            }
-        }
-
-        public IContextCarrier Deserialize(string text)
-        {
-            string[] parts = text?.Split("|".ToCharArray(), 8);
-            if (parts?.Length == 8)
-            {
-                _traceSegmentId = new ID(parts[0]);
-                _spanId = int.Parse(parts[1]);
-                _parentApplicationInstanceId = int.Parse(parts[2]);
-                _entryApplicationInstanceId = int.Parse(parts[3]);
-                _peerHost = parts[4];
-                _entryOperationName = parts[5];
-                _parentOperationName = parts[6];
-                _primaryDistributedTraceId = new PropagatedTraceId(parts[7]);
-            }
-
-            return this;
-        }
-
-        public string Serialize()
-        {
-            if (!IsValid)
-            {
-                return string.Empty;
-            }
-
-            return string.Join("|",
-                TraceSegmentId.Encode,
-                SpanId.ToString(),
-                ParentApplicationInstanceId.ToString(),
-                EntryApplicationInstanceId.ToString(),
-                PeerHost,
-                EntryOperationName,
-                ParentOperationName,
-                PrimaryDistributedTraceId.Encode);
-        }
-
-        public DistributedTraceId PrimaryDistributedTraceId => _primaryDistributedTraceId;
-
-        public CarrierItem Items
-        {
-            get
-            {
-                var carrierItem = new SW3CarrierItem(this, null, _namespace);
-                var head = new CarrierItemHead(carrierItem, _namespace);
-                return head;
-            }
-        }
-
-        public void SetDistributedTraceIds(IEnumerable<DistributedTraceId> distributedTraceIds)
-        {
-            _primaryDistributedTraceId = distributedTraceIds.FirstOrDefault();
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/ContextManager.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Collections.Generic;
-using System.Threading;
-using SkyWalking.Context.Trace;
-
-namespace SkyWalking.Context
-{
-    /// <summary>
-    /// Context manager controls the whole context of tracing. Since .NET server application runs as same as Java,
-    /// We also provide the CONTEXT propagation based on ThreadLocal mechanism.
-    /// Meaning, each segment also related to singe thread.
-    /// </summary>
-    public class ContextManager : ITracingContextListener, IIgnoreTracerContextListener
-    {
-        static ContextManager()
-        {
-            var manager = new ContextManager();
-            TracingContext.ListenerManager.Add(manager);
-            IgnoredTracerContext.ListenerManager.Add(manager);
-        }
-
-        private static readonly AsyncLocal<ITracerContext> _context = new AsyncLocal<ITracerContext>();
-
-        private static ITracerContext GetOrCreateContext(string operationName, bool forceSampling)
-        {
-            var context = _context.Value;
-            if (context == null)
-            {
-                if (string.IsNullOrEmpty(operationName))
-                {
-                    // logger.debug("No operation name, ignore this trace.");
-                    _context.Value = new IgnoredTracerContext();
-                }
-                else
-                {
-                    if (RuntimeEnvironment.Instance.Initialized)
-                    {
-//                        var suffixIdx = operationName.LastIndexOf('.');
-//                        if (suffixIdx > -1 && AgentConfig.IgnoreSuffix.Contains(operationName.Substring(suffixIdx)))
-//                        {
-//                            _context.Value = new IgnoredTracerContext();
-//                        }
-//                        else
-//                        {
-                            var sampler = DefaultSampler.Instance;
-                            if (forceSampling || sampler.Sampled())
-                            {
-                                _context.Value = new TracingContext();
-                            }
-                            else
-                            {
-                                _context.Value = new IgnoredTracerContext();
-                            }
-//                        }
-                    }
-                    else
-                    {
-                        _context.Value = new IgnoredTracerContext();
-                    }
-                }
-            }
-
-            return _context.Value;
-        }
-
-        private static ITracerContext Context => _context.Value;
-        
-
-        public static string GlobalTraceId
-        {
-            get
-            {
-                if (_context.Value != null)
-                {
-                    return _context.Value.GetReadableGlobalTraceId();
-                }
-
-                return "N/A";
-            }
-        }
-
-        public static IContextSnapshot Capture => _context.Value?.Capture;
-
-        public static IDictionary<string, object> ContextProperties => _context.Value?.Properties;
-
-        public static ISpan CreateEntrySpan(string operationName, IContextCarrier carrier)
-        {
-            var samplingService = DefaultSampler.Instance;
-            if (carrier != null && carrier.IsValid)
-            {
-                samplingService.ForceSampled();
-                var context = GetOrCreateContext(operationName, true);
-                var span = context.CreateEntrySpan(operationName);
-                context.Extract(carrier);
-                return span;
-            }
-            else
-            {
-                var context = GetOrCreateContext(operationName, false);
-
-                return context.CreateEntrySpan(operationName);
-            }
-        }
-
-        public static ISpan CreateLocalSpan(string operationName)
-        {
-            var context = GetOrCreateContext(operationName, false);
-            return context.CreateLocalSpan(operationName);
-        }
-
-        public static ISpan CreateExitSpan(string operationName, IContextCarrier carrier, string remotePeer)
-        {
-            var context = GetOrCreateContext(operationName, false);
-            var span = context.CreateExitSpan(operationName, remotePeer);
-            context.Inject(carrier);
-            return span;
-        }
-
-        public static ISpan CreateExitSpan(string operationName, string remotePeer)
-        {
-            var context = GetOrCreateContext(operationName, false);
-            var span = context.CreateExitSpan(operationName, remotePeer);
-            return span;
-        }
-
-        public static void Inject(IContextCarrier carrier)
-        {
-            Context?.Inject(carrier);
-        }
-
-        public static void Extract(IContextCarrier carrier)
-        {
-            Context?.Extract(carrier);
-        }
-
-        public static void Continued(IContextSnapshot snapshot)
-        {
-            if (snapshot.IsValid && !snapshot.IsFromCurrent)
-            {
-                Context?.Continued(snapshot);
-            }
-        }
-
-        public static void StopSpan()
-        {
-            StopSpan(ActiveSpan);
-        }
-
-        public static ISpan ActiveSpan
-        {
-            get { return Context?.ActiveSpan; }
-        }
-
-        public static ITracerContext ActiveContext
-        {
-            get
-            {
-                return Context;
-            }
-        }
-
-        public static void StopSpan(ISpan span, ITracerContext context=null)
-        {
-            if (Context != null)
-            {
-                Context.StopSpan(span);
-            }
-            else if (context != null)
-            {
-                context.StopSpan(span);
-            }
-        }
-
-        public void AfterFinished(ITraceSegment traceSegment)
-        {
-            _context.Value = null;
-        }
-
-        public void AfterFinish(ITracerContext tracerContext)
-        {
-            _context.Value = null;
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/ContextSnapshot.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Collections.Generic;
-using System.Linq;
-using SkyWalking.Context.Ids;
-
-namespace SkyWalking.Context
-{
-    public class ContextSnapshot : IContextSnapshot
-    {
-        /// <summary>
-        /// Trace Segment Id of the parent trace segment
-        /// </summary>
-        private readonly ID _traceSegmentId;
-
-        /// <summary>
-        /// span id of the parent span , in parent trace segment
-        /// </summary>
-        private readonly int _spanId = -1;
-
-        private string _entryOperationName;
-        private string _parentOperationName;
-
-        private readonly DistributedTraceId _primaryDistributedTraceId;
-        private NullableValue _entryApplicationInstanceId = NullableValue.Null;
-
-        public ContextSnapshot(ID traceSegmentId, int spanId, IEnumerable<DistributedTraceId> distributedTraceIds)
-        {
-            _traceSegmentId = traceSegmentId;
-            _spanId = spanId;
-            _primaryDistributedTraceId = distributedTraceIds?.FirstOrDefault();
-        }
-
-        public string EntryOperationName
-        {
-            get => _entryOperationName;
-            set => _entryOperationName = "#" + value;
-        }
-
-        public string ParentOperationName
-        {
-            get => _parentOperationName;
-            set => _parentOperationName = "#" + value;
-        }
-
-        public DistributedTraceId DistributedTraceId => _primaryDistributedTraceId;
-
-        public int EntryApplicationInstanceId
-        {
-            get => _entryApplicationInstanceId.Value;
-            set => _entryApplicationInstanceId = new NullableValue(value);
-        }
-
-        public int SpanId => _spanId;
-
-        public bool IsFromCurrent => _traceSegmentId.Equals(ContextManager.Capture.TraceSegmentId);
-
-        public bool IsValid => _traceSegmentId != null
-                               && _spanId > -1
-                               && _entryApplicationInstanceId.HasValue
-                               && _primaryDistributedTraceId != null
-                               && string.IsNullOrEmpty(_entryOperationName)
-                               && string.IsNullOrEmpty(_parentOperationName);
-
-        public ID TraceSegmentId => _traceSegmentId;
-
-        public int EntryOperationId
-        {
-            set => _entryOperationName = value + "";
-        }
-        
-        public int ParentOperationId 
-        {
-            set => _parentOperationName = value + "";
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/Ids/NewDistributedTraceId.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-namespace SkyWalking.Context.Ids
-{
-    public class NewDistributedTraceId : DistributedTraceId
-    {
-        public NewDistributedTraceId()
-            :base(GlobalIdGenerator.Generate())
-        {
-        }
-    }
-}

src/SkyWalking.Core/Context/Ids/PropagatedTraceId.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-namespace SkyWalking.Context.Ids
-{
-    /// <summary>
-    /// The <code>PropagatedTraceId</code> represents a {@link DistributedTraceId}, which is propagated from the peer.
-    /// </summary>
-    public class PropagatedTraceId : DistributedTraceId
-    {
-        public PropagatedTraceId(string id)
-            :base(id)
-        {
-        }
-    }
-}

src/SkyWalking.Core/Context/IgnoredTracerContext.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System;
-using System.Collections.Generic;
-using System.Runtime.CompilerServices;
-using SkyWalking.Context.Trace;
-using SkyWalking.Utils;
-
-namespace SkyWalking.Context
-{
-    public class IgnoredTracerContext : ITracerContext
-    {
-        private static readonly NoopSpan noopSpan = new NoopSpan();
-        private static readonly NoopEntrySpan noopEntrySpan=new NoopEntrySpan();
-
-        private readonly Stack<ISpan> _spans = new Stack<ISpan>();
-        
-        public void Inject(IContextCarrier carrier)
-        {
-        }
-
-        public void Extract(IContextCarrier carrier)
-        {
-        }
-
-        public IContextSnapshot Capture { get; }
-
-        public ISpan ActiveSpan
-        {
-            get
-            {
-                _spans.TryPeek(out var span);
-                return span;
-            }
-        }
-
-        public IDictionary<string, object> Properties { get; } = new Dictionary<string, object>();
-
-        public void Continued(IContextSnapshot snapshot)
-        {
-        }
-
-        public string GetReadableGlobalTraceId()
-        {
-            return string.Empty;
-        }
-
-        public ISpan CreateEntrySpan(string operationName)
-        {
-            _spans.Push(noopEntrySpan);
-            return noopEntrySpan;
-        }
-
-        public ISpan CreateLocalSpan(string operationName)
-        {
-            _spans.Push(noopSpan);
-            return noopSpan;
-        }
-
-        public ISpan CreateExitSpan(string operationName, string remotePeer)
-        {
-            var exitSpan = new NoopExitSpan(remotePeer);
-            _spans.Push(exitSpan);
-            return exitSpan;
-        }
-
-        public void StopSpan(ISpan span)
-        {
-            _spans.TryPop(out _);
-            if (_spans.Count == 0)
-            {
-                ListenerManager.NotifyFinish(this);
-                foreach (var item in Properties)
-                {
-                    if (item.Value is IDisposable disposable)
-                    {
-                        disposable.Dispose();
-                    }
-                }
-            }
-        }
-
-        public static class ListenerManager
-        {
-            private static readonly List<IIgnoreTracerContextListener> _listeners = new List<IIgnoreTracerContextListener>();
-
-            [MethodImpl(MethodImplOptions.Synchronized)]
-            public static void Add(IIgnoreTracerContextListener listener)
-            {
-                _listeners.Add(listener);
-            }
-
-            public static void NotifyFinish(ITracerContext tracerContext)
-            {
-                foreach (var listener in _listeners)
-                {
-                    listener.AfterFinish(tracerContext);
-                }
-            }
-
-            [MethodImpl(MethodImplOptions.Synchronized)]
-            public static void Remove(IIgnoreTracerContextListener listener)
-            {
-                _listeners.Remove(listener);
-            }
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/SW3CarrierItem.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System;
-
-namespace SkyWalking.Context
-{
-    public class SW3CarrierItem : CarrierItem
-    {
-        private const string HEADER_NAME = "sw3";
-        private readonly IContextCarrier _carrier;
-
-        public SW3CarrierItem(IContextCarrier carrier, CarrierItem next, string @namespace)
-            : base(HEADER_NAME, carrier.Serialize(), next, @namespace)
-        {
-            _carrier = carrier;
-        }
-
-        public override string HeadValue
-        {
-            get => base.HeadValue;
-            set => _carrier.Deserialize(value);
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/Tag/Tags.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-namespace SkyWalking.Context.Tag
-{
-    /// <summary>
-    /// The span tags are supported by sky-walking engine.
-    /// As default, all tags will be stored, but these ones have particular meanings.
-    /// </summary>
-    public static class Tags
-    {
-        public static readonly StringTag Url = new StringTag("url");
-
-        /// <summary>
-        /// STATUS_CODE records the http status code of the response.
-        /// </summary>
-        public static readonly StringTag StatusCode = new StringTag("status_code");
-
-        /// <summary>
-        /// DB_TYPE records database type, such as sql, redis, cassandra and so on.
-        /// </summary>
-        public static readonly StringTag DbType = new StringTag("db.type");
-
-        /// <summary>
-        /// DB_INSTANCE records database instance name.
-        /// </summary>
-        public static readonly StringTag DbInstance = new StringTag("db.instance");
-
-        /// <summary>
-        /// DB_STATEMENT records the sql statement of the database access.
-        /// </summary>
-        public static readonly StringTag DbStatement = new StringTag("db.statement");
-
-        /// <summary>
-        /// DB_BIND_VARIABLES records the bind variables of sql statement.
-        /// </summary>
-        public static readonly StringTag DbBindVariables = new StringTag("db.bind_vars");
-
-        /// <summary>
-        /// MQ_BROKER records the broker address of message-middleware
-        /// </summary>
-        public static readonly StringTag MqBorker = new StringTag("mq.broker");
-
-        /// <summary>
-        /// MQ_TOPIC records the topic name of message-middleware
-        /// </summary>
-        public static readonly StringTag MqTopic = new StringTag("mq.topic");
-
-        public static class HTTP
-        {
-            public static readonly StringTag Method = new StringTag("http.method");
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/Trace/EntrySpan.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using SkyWalking.Components;
-
-namespace SkyWalking.Context.Trace
-{
-    public class EntrySpan : StackBasedTracingSpan
-    {
-        private int _currentMaxDepth;
-
-        public EntrySpan(int spanId, int parentSpanId, string operationName)
-            : base(spanId, parentSpanId, operationName)
-        {
-            _stackDepth = 0;
-        }
-
-        public EntrySpan(int spanId, int parentSpanId, int operationId)
-            : base(spanId, parentSpanId, operationId)
-        {
-            _stackDepth = 0;
-        }
-
-        public override bool IsEntry => true;
-
-        public override bool IsExit => false;
-
-        public override ISpan Start()
-        {
-            if ((_currentMaxDepth = ++_stackDepth) == 1)
-            {
-                base.Start();
-            }
-            ClearWhenRestart();
-            return this;
-        }
-
-        public override ISpan Tag(string key, string value)
-        {
-            if (_stackDepth == _currentMaxDepth)
-            {
-                base.Tag(key, value);
-            }
-            return this;
-        }
-
-        public override ISpan SetLayer(SpanLayer layer)
-        {
-            if (_stackDepth == _currentMaxDepth)
-            {
-                return base.SetLayer(layer);
-            }
-            return this;
-        }
-
-        public override ISpan SetComponent(IComponent component)
-        {
-            if (_stackDepth == _currentMaxDepth)
-            {
-                return base.SetComponent(component);
-            }
-            return this;
-        }
-
-        public override ISpan SetComponent(string componentName)
-        {
-            if (_stackDepth == _currentMaxDepth)
-            {
-                return base.SetComponent(componentName);
-            }
-            return this;
-        }
-
-        public override string OperationName
-        {
-            get
-            {
-                return base.OperationName;
-            }
-            set
-            {
-                if (_stackDepth == _currentMaxDepth)
-                {
-                    base.OperationName = value;
-                }
-            }
-        }
-
-        public override int OperationId
-        {
-            get
-            {
-                return base.OperationId;
-            }
-            set
-            {
-                if (_stackDepth == _currentMaxDepth)
-                {
-                    base.OperationId = value;
-                }
-            }
-        }
-
-        private void ClearWhenRestart()
-        {
-            _componentId = 0;
-            _componentName = null;
-            _layer = null;
-            _logs = null;
-            _tags = null;
-        }
-    }
-}

src/SkyWalking.Core/Context/Trace/ExitSpan.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System;
-using SkyWalking.Transport;
-using SkyWalking.Components;
-
-namespace SkyWalking.Context.Trace
-{
-    public class ExitSpan : StackBasedTracingSpan, IWithPeerInfo
-    {
-        private readonly string _peer;
-        private readonly int _peerId;
-
-        public ExitSpan(int spanId, int parentSpanId, String operationName, String peer)
-            : base(spanId, parentSpanId, operationName)
-        {
-            _peer = peer;
-            _peerId = 0;
-        }
-
-        public ExitSpan(int spanId, int parentSpanId, int operationId, int peerId)
-            : base(spanId, parentSpanId, operationId)
-        {
-            _peer = null;
-            _peerId = peerId;
-        }
-
-        public ExitSpan(int spanId, int parentSpanId, int operationId, String peer)
-            : base(spanId, parentSpanId, operationId)
-        {
-            _peer = peer;
-            _peerId = 0;
-        }
-
-        public ExitSpan(int spanId, int parentSpanId, String operationName, int peerId)
-            : base(spanId, parentSpanId, operationName)
-        {
-            _peer = null;
-            _peerId = peerId;
-        }
-
-        public override bool IsEntry => false;
-
-        public override bool IsExit => true;
-
-        public int PeerId => _peerId;
-
-        public string Peer => _peer;
-
-        public override ISpan Start()
-        {
-            if (++_stackDepth == 1)
-            {
-                base.Start();
-            }
-
-            return base.Start();
-        }
-
-        public override ISpan Tag(string key, string value)
-        {
-            if (_stackDepth == 1)
-            {
-                base.Tag(key, value);
-            }
-
-            return this;
-        }
-
-        public override ISpan SetLayer(SpanLayer layer)
-        {
-            if (_stackDepth == 1)
-            {
-                return base.SetLayer(layer);
-            }
-
-            return this;
-        }
-
-        public override ISpan SetComponent(IComponent component)
-        {
-            if (_stackDepth == 1)
-            {
-                return base.SetComponent(component);
-            }
-
-            return this;
-        }
-
-        public override ISpan SetComponent(string componentName)
-        {
-            return _stackDepth == 1 ? base.SetComponent(componentName) : this;
-        }
-
-        public override string OperationName
-        {
-            get => base.OperationName;
-            set
-            {
-                if (_stackDepth == 1)
-                {
-                    base.OperationName = value;
-                }
-            }
-        }
-
-        public override int OperationId
-        {
-            get => base.OperationId;
-            set
-            {
-                if (_stackDepth == 1)
-                {
-                    base.OperationId = value;
-                }
-            }
-        }
-
-        public override SpanRequest Transform()
-        {
-            var spanObject = base.Transform();
-
-            spanObject.Peer = new StringOrIntValue(_peerId, _peer);
-
-            return spanObject;
-        }
-    }
-}

src/SkyWalking.Core/Context/Trace/LocalSpan.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-namespace SkyWalking.Context.Trace
-{
-    public class LocalSpan : StackBasedTracingSpan
-    {
-        public LocalSpan(int spanId, int parentSpanId, string operationName) : base(spanId, parentSpanId, operationName)
-        {
-        }
-
-        public LocalSpan(int spanId, int parentSpanId, int operationId) : base(spanId, parentSpanId, operationId)
-        {
-        }
-
-        public override bool IsEntry => false;
-
-        public override bool IsExit => false;
-    }
-}

src/SkyWalking.Core/Context/Trace/NoopEntrySpan.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-namespace SkyWalking.Context.Trace
-{
-    public class NoopEntrySpan:NoopSpan
-    {
-        public override bool IsEntry { get; } = true;
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/Trace/TraceSegment.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Collections.Generic;
-using System.Linq;
-using SkyWalking.Transport;
-using SkyWalking.Context.Ids;
-
-namespace SkyWalking.Context.Trace
-{
-    public class TraceSegment : ITraceSegment
-    {
-        private readonly IList<ITraceSegmentRef> _refs;
-        private readonly IList<AbstractTracingSpan> _spans;
-        private readonly DistributedTraceIdCollection _relatedGlobalTraces;
-        private bool _isSizeLimited;
-
-        public int ApplicationId => RuntimeEnvironment.Instance.ServiceId.Value;
-
-        public int ApplicationInstanceId => RuntimeEnvironment.Instance.ServiceInstanceId.Value;
-
-        public IEnumerable<ITraceSegmentRef> Refs => _refs;
-
-        public IEnumerable<DistributedTraceId> RelatedGlobalTraces => _relatedGlobalTraces.GetRelatedGlobalTraces();
-
-        public ID TraceSegmentId { get; }
-
-        public bool HasRef => _refs.Count > 0;
-
-        public bool IsIgnore { get; set; }
-
-        public bool IsSingleSpanSegment => _spans.Count == 1;
-
-        public TraceSegment()
-        {
-            TraceSegmentId = GlobalIdGenerator.Generate();
-            _spans = new List<AbstractTracingSpan>();
-            _relatedGlobalTraces = new DistributedTraceIdCollection();
-            _relatedGlobalTraces.Append(new NewDistributedTraceId());
-            _refs = new List<ITraceSegmentRef>();
-        }
-
-        public void Archive(AbstractTracingSpan finishedSpan)
-        {
-            _spans.Add(finishedSpan);
-        }
-
-        public ITraceSegment Finish(bool isSizeLimited)
-        {
-            _isSizeLimited = isSizeLimited;
-            return this;
-        }
-
-        /// <summary>
-        /// Establish the link between this segment and its parents.
-        /// </summary>
-        public void Ref(ITraceSegmentRef refSegment)
-        {
-            if (!_refs.Contains(refSegment))
-            {
-                _refs.Add(refSegment);
-            }
-        }
-
-        public void RelatedGlobalTrace(DistributedTraceId distributedTraceId)
-        {
-            _relatedGlobalTraces.Append(distributedTraceId);
-        }
-
-        public SegmentRequest Transform()
-        {
-            var upstreamSegment = new SegmentRequest
-            {
-                UniqueIds = _relatedGlobalTraces.GetRelatedGlobalTraces()
-                    .Select(x => x.ToUniqueId()).ToArray()
-            };
-
-            upstreamSegment.Segment = new SegmentObjectRequest
-            {
-                SegmentId = TraceSegmentId.Transform(),
-                Spans = _spans.Select(x => x.Transform()).ToArray(),
-                ServiceId = ApplicationId,
-                ServiceInstanceId = ApplicationInstanceId
-            };
-            
-            return upstreamSegment;
-        }
-
-        public override string ToString()
-        {
-            return "TraceSegment{"
-                   +
-                   $"traceSegmentId='{TraceSegmentId}', refs={_refs}, spans={_spans}, relatedGlobalTraces={_relatedGlobalTraces}"
-                   + "}";
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Context/Trace/TraceSegmentRef.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Linq;
-using SkyWalking.Transport;
-using SkyWalking.Config;
-using SkyWalking.Context.Ids;
-
-namespace SkyWalking.Context.Trace
-{
-    public class TraceSegmentRef : ITraceSegmentRef
-    {
-        private readonly SegmentRefType _type;
-        private readonly ID _traceSegmentId;
-        private readonly int _spanId = -1;
-        private readonly int _peerId = 0;
-        private readonly string _peerHost;
-        private readonly int _entryApplicationInstanceId = 0;
-        private readonly int _parentApplicationInstanceId = 0;
-        private readonly string _entryOperationName;
-        private readonly int _entryOperationId = 0;
-        private readonly string _parentOperationName;
-        private readonly int _parentOperationId = 0;
-
-        public TraceSegmentRef(IContextCarrier carrier)
-        {
-            _type = SegmentRefType.CrossProcess;
-            _traceSegmentId = carrier.TraceSegmentId;
-            _spanId = carrier.SpanId;
-            _parentApplicationInstanceId = carrier.ParentApplicationInstanceId;
-            _entryApplicationInstanceId = carrier.EntryApplicationInstanceId;
-            string host = carrier.PeerHost;
-            if (host.ToCharArray()[0] == '#')
-            {
-                _peerHost = host.Substring(1);
-            }
-            else
-            {
-                int.TryParse(host, out _peerId);
-            }
-
-            string entryOperationName = carrier.EntryOperationName;
-            if (entryOperationName.First() == '#')
-            {
-                _entryOperationName = entryOperationName.Substring(1);
-            }
-            else
-            {
-                int.TryParse(entryOperationName, out _entryOperationId);
-            }
-
-            string parentOperationName = carrier.EntryOperationName;
-            if (parentOperationName.First() == '#')
-            {
-                _parentOperationName = parentOperationName.Substring(1);
-            }
-            else
-            {
-                int.TryParse(parentOperationName, out _parentOperationId);
-            }
-        }
-
-        public TraceSegmentRef(IContextSnapshot contextSnapshot)
-        {
-            _type = SegmentRefType.CrossThread;
-            _traceSegmentId = contextSnapshot.TraceSegmentId;
-            _spanId = contextSnapshot.SpanId;
-            _parentApplicationInstanceId = RuntimeEnvironment.Instance.ServiceInstanceId.Value;
-            _entryApplicationInstanceId = contextSnapshot.EntryApplicationInstanceId;
-            string entryOperationName = contextSnapshot.EntryOperationName;
-            if (entryOperationName.First() == '#')
-            {
-                _entryOperationName = entryOperationName.Substring(1);
-            }
-            else
-            {
-                int.TryParse(entryOperationName, out _entryOperationId);
-            }
-
-            string parentOperationName = contextSnapshot.ParentOperationName;
-            if (parentOperationName.First() == '#')
-            {
-                _parentOperationName = parentOperationName.Substring(1);
-            }
-            else
-            {
-                int.TryParse(parentOperationName, out _parentOperationId);
-            }
-        }
-
-        public bool Equals(ITraceSegmentRef other)
-        {
-            if (other == null)
-            {
-                return false;
-            }
-
-            if (other == this)
-            {
-                return true;
-            }
-
-            if (!(other is TraceSegmentRef segmentRef))
-            {
-                return false;
-            }
-
-            if (_spanId != segmentRef._spanId)
-            {
-                return false;
-            }
-
-            return _traceSegmentId.Equals(segmentRef._traceSegmentId);
-        }
-
-        public override bool Equals(object obj)
-        {
-            var other = obj as ITraceSegmentRef;
-            return Equals(other);
-        }
-
-        public override int GetHashCode()
-        {
-            int result = _traceSegmentId.GetHashCode();
-            result = 31 * result + _spanId;
-            return result;
-        }
-
-        public string EntryOperationName => _entryOperationName;
-
-        public int EntryOperationId => _entryOperationId;
-
-        public int EntryApplicationInstanceId => _entryApplicationInstanceId;
-
-        public SegmentReferenceRequest Transform()
-        {
-            SegmentReferenceRequest segmentReference = new SegmentReferenceRequest();
-            if (_type == SegmentRefType.CrossProcess)
-            {
-                segmentReference.RefType = (int) SegmentRefType.CrossProcess;
-                segmentReference.NetworkAddress = new StringOrIntValue(_peerId, _peerHost);
-            }
-            else
-            {
-                segmentReference.RefType = (int) SegmentRefType.CrossThread;
-                segmentReference.NetworkAddress = new StringOrIntValue();
-            }
-
-            segmentReference.ParentServiceInstanceId = _parentApplicationInstanceId;
-            segmentReference.EntryServiceInstanceId = _entryApplicationInstanceId;
-            segmentReference.ParentSegmentId = _traceSegmentId.Transform();
-            segmentReference.ParentSpanId = _spanId;
-
-            segmentReference.EntryEndpointName = new StringOrIntValue(_entryOperationId, _entryOperationName);
-
-            segmentReference.ParentEndpointName = new StringOrIntValue(_parentOperationId, _parentOperationName);
-
-            return segmentReference;
-        }
-    }
-}

src/SkyWalking.Core/Context/TraceContextCarrierItem.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-namespace SkyWalking.Context
-{
-    public class TraceContextCarrierItem : CarrierItem
-    {
-        private const string HEAD_NAME = "Trace-Context";
-
-        public TraceContextCarrierItem(string headValue, CarrierItem next, string @namespace)
-            : base(HEAD_NAME, headValue, next, @namespace)
-        {
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/DefaultSampler.cs

-/*
- * Licensed to the OpenSkywalking under one or more
- * contributor license agreements.  See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License.  You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-using System.Runtime.CompilerServices;
-using SkyWalking.Utils;
-
-namespace SkyWalking
-{
-    public class DefaultSampler : ISampler
-    {
-        public static DefaultSampler Instance { get; } = new DefaultSampler();
-        
-        private readonly AtomicInteger _idx = new AtomicInteger();
-        
-        private int _samplePer3Secs;
-        private bool _sample_on;
-
-        public bool Sampled()
-        {
-            if (!_sample_on)
-            {
-                return true;
-            }
-
-            return _idx.Increment() < _samplePer3Secs;
-        }
-
-        public void ForceSampled()
-        {
-            if (_sample_on)
-            {
-                _idx.Increment();
-            }
-        }
-
-        [MethodImpl(MethodImplOptions.Synchronized)]
-        internal void SetSamplePer3Secs(int samplePer3Secs)
-        {
-            _samplePer3Secs = samplePer3Secs;
-            _sample_on = samplePer3Secs > -1;
-        }
-
-        internal void Reset()
-        {
-            _idx.Value = 0;
-        }
-    }
-}
\ No newline at end of file

src/SkyWalking.Core/Diagnostics/TracingDiagnosticProcessorObserver.cs

@@ -19,8 +19,8 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using SkyWalking.Common;
 using SkyWalking.Logging;
-using SkyWalking.Utils;
 
 namespace SkyWalking.Diagnostics
 {

src/SkyWalking.Core/SkyWalkingAgentStartup.cs → src/SkyWalking.Core/InstrumentStartup.cs

@@ -2,7 +2,7 @@
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
@@ -27,17 +27,17 @@ using SkyWalking.Logging;
 
 namespace SkyWalking
 {
-    public class SkyWalkingAgentStartup : ISkyWalkingAgentStartup
+    public class InstrumentStartup : IInstrumentStartup
     {
         private readonly TracingDiagnosticProcessorObserver _observer;
         private readonly IEnumerable<IExecutionService> _services;
         private readonly ILogger _logger;
 
-        public SkyWalkingAgentStartup(TracingDiagnosticProcessorObserver observer, IEnumerable<IExecutionService> services, ILoggerFactory loggerFactory)
+        public InstrumentStartup(TracingDiagnosticProcessorObserver observer, IEnumerable<IExecutionService> services, ILoggerFactory loggerFactory)
         {
             _observer = observer;
             _services = services;
-            _logger = loggerFactory.CreateLogger(typeof(SkyWalkingAgentStartup));
+            _logger = loggerFactory.CreateLogger(typeof(InstrumentStartup));
         }
 
         public async Task StartAsync(CancellationToken cancellationToken = default(CancellationToken))

src/SkyWalking.Core/RuntimeEnvironment.cs

@@ -2,7 +2,7 @@
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
+ * The OpenSkywalking licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
@@ -17,6 +17,7 @@
  */
 
 using System;
+using SkyWalking.Common;
 
 namespace SkyWalking
 {

src/SkyWalking.Abstractions/Context/Utils/ExceptionExtensions.cs → src/SkyWalking.Core/Sampling/RandomSamplingInterceptor.cs

-/*
+/*
  * Licensed to the OpenSkywalking under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
@@ -17,40 +17,35 @@
  */
 
 using System;
-using System.ComponentModel;
-using System.Diagnostics;
-using System.Text;
+using SkyWalking.Config;
+using SkyWalking.Tracing;
 
-namespace SkyWalking.Context
+namespace SkyWalking.Sampling
 {
-    public static class ExceptionExtensions
+    public class RandomSamplingInterceptor : ISamplingInterceptor
     {
-        public static string ConvertToString(Exception exception, int maxLength)
-        {
-            var message = new StringBuilder();
+        private readonly Random _random;
+        private readonly int _samplingRate;
+        private readonly bool _sample_on;
 
-            while (exception != null)
+        public RandomSamplingInterceptor(IConfigAccessor configAccessor)
         {
-                message.Append(exception.Message);
-
-                PrintStackFrame(message, exception.StackTrace, maxLength, out var overMaxLength);
-
-                if (overMaxLength)
+            var percentage = configAccessor.Get<SamplingConfig>().Percentage;
+            _sample_on = percentage > 0;
+            if (_sample_on)
             {
-                    break;
+                _samplingRate = (int)(percentage * 100d);
             }
-
-                exception = exception.InnerException;
+            _random = new Random();
         }
 
-            return message.ToString();
-        }
+        public int Priority { get; } = int.MinValue + 1000;
 
-        private static void PrintStackFrame(StringBuilder message, string stackTrace,
-            int maxLength, out bool overMaxLength)
+        public bool Invoke(SamplingContext samplingContext, Sampler next)
         {
-            message.AppendLine(stackTrace);
-            overMaxLength = message.Length > maxLength;
+            if (!_sample_on) return next(samplingContext);
+            var r = _random.Next(10000);
+            return r <= _samplingRate && next(samplingContext);
         }
     }
 }
\ No newline at end of file

src/SkyWalking.Core/Service/SamplingRefreshService.cs → src/SkyWalking.Core/Sampling/SimpleCountSamplingInterceptor.cs

@@ -19,31 +19,50 @@
 using System;
 using System.Threading;
 using System.Threading.Tasks;
+using SkyWalking.Common;
 using SkyWalking.Config;
 using SkyWalking.Logging;
+using SkyWalking.Tracing;
 
-namespace SkyWalking.Service
+namespace SkyWalking.Sampling
 {
-    public class SamplingRefreshService : ExecutionService
+    public class SimpleCountSamplingInterceptor : ExecutionService, ISamplingInterceptor
     {
-        private readonly SamplingConfig _config;
+        private readonly bool _sample_on;
+        private readonly int _samplePer3Secs;
+        private readonly AtomicInteger _idx = new AtomicInteger();
 
-        public SamplingRefreshService(IConfigAccessor configAccessor,
-            IRuntimeEnvironment runtimeEnvironment, ILoggerFactory loggerFactory)
-            : base(runtimeEnvironment, loggerFactory)
+        public SimpleCountSamplingInterceptor(IConfigAccessor configAccessor,IRuntimeEnvironment runtimeEnvironment, ILoggerFactory loggerFactory) :
+            base(runtimeEnvironment, loggerFactory)
         {
-            _config = configAccessor.Get<SamplingConfig>();
-            DefaultSampler.Instance.SetSamplePer3Secs(_config.SamplePer3Secs);
+            var samplingConfig = configAccessor.Get<SamplingConfig>();
+            _samplePer3Secs = samplingConfig.SamplePer3Secs;
+            _sample_on = _samplePer3Secs > -1;
+        }
+
+        public int Priority { get; } = int.MinValue + 999;
+
+        public bool Invoke(SamplingContext samplingContext, Sampler next)
+        {
+            if (!_sample_on) return next(samplingContext);
+            return _idx.Increment() <= _samplePer3Secs && next(samplingContext);
         }
 
         protected override TimeSpan DueTime { get; } = TimeSpan.Zero;
 
         protected override TimeSpan Period { get; } = TimeSpan.FromSeconds(3);
 
+        protected override bool CanExecute() => _sample_on && base.CanExecute();
+
         protected override Task ExecuteAsync(CancellationToken cancellationToken)
         {
-            DefaultSampler.Instance.Reset();
+            Reset();
             return Task.CompletedTask;
         }
+        
+        private void Reset()
+        {
+            _idx.Value = 0;
+        }
     }
 }
\ No newline at end of file

src/SkyWalking.Core/Service/RegisterService.cs

@@ -20,16 +20,16 @@ using System;
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
+using SkyWalking.Common;
 using SkyWalking.Config;
 using SkyWalking.Logging;
 using SkyWalking.Transport;
-using SkyWalking.Utils;
 
 namespace SkyWalking.Service
 {
     public class RegisterService : ExecutionService
     {
-        private readonly InstrumentationConfig _config;
+        private readonly InstrumentConfig _config;
         private readonly IServiceRegister _serviceRegister;
         private readonly TransportConfig _transportConfig;
 
@@ -38,7 +38,7 @@ namespace SkyWalking.Service
             loggerFactory)
         {
             _serviceRegister = serviceRegister;
-            _config = configAccessor.Get<InstrumentationConfig>();
+            _config = configAccessor.Get<InstrumentConfig>();
             _transportConfig = configAccessor.Get<TransportConfig>();
         }
 

src/SkyWalking.Core/Service/SegmentReportService.cs

@@ -20,14 +20,12 @@ using System;
 using System.Threading;
 using System.Threading.Tasks;
 using SkyWalking.Config;
-using SkyWalking.Context;
-using SkyWalking.Context.Trace;
 using SkyWalking.Logging;
 using SkyWalking.Transport;
 
 namespace SkyWalking.Service
 {
-    public class SegmentReportService : ExecutionService, ITracingContextListener
+    public class SegmentReportService : ExecutionService
     {
         private readonly TransportConfig _config;
         private readonly ISegmentDispatcher _dispatcher;
@@ -39,7 +37,6 @@ namespace SkyWalking.Service
             _dispatcher = dispatcher;
             _config = configAccessor.Get<TransportConfig>();
             Period = TimeSpan.FromMilliseconds(_config.Interval);
-            TracingContext.ListenerManager.Add(this);
         }
 
         protected override TimeSpan DueTime { get; } = TimeSpan.FromSeconds(3);
@@ -54,14 +51,7 @@ namespace SkyWalking.Service
         protected override Task Stopping(CancellationToken cancellationToke)
         {
             _dispatcher.Close();
-            TracingContext.ListenerManager.Remove(this);
             return Task.CompletedTask;
         }
-
-        public void AfterFinished(ITraceSegment traceSegment)
-        {
-            if (!traceSegment.IsIgnore)
-                _dispatcher.Dispatch(traceSegment.Transform());
-        }
     }
 }
\ No newline at end of file

src/SkyWalking.Core/Service/ServiceDiscoveryV5Service.cs

@@ -20,16 +20,16 @@ using System;
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
+using SkyWalking.Common;
 using SkyWalking.Config;
 using SkyWalking.Logging;
 using SkyWalking.Transport;
-using SkyWalking.Utils;
 
 namespace SkyWalking.Service
 {
     public class ServiceDiscoveryV5Service : ExecutionService
     {
-        private readonly InstrumentationConfig _config;
+        private readonly InstrumentConfig _config;
         private readonly TransportConfig _transportConfig;
         private readonly ISkyWalkingClientV5 _skyWalkingClient;
 
@@ -41,7 +41,7 @@ namespace SkyWalking.Service
             IRuntimeEnvironment runtimeEnvironment, ILoggerFactory loggerFactory)
             : base(runtimeEnvironment, loggerFactory)
         {
-            _config = configAccessor.Get<InstrumentationConfig>();
+            _config = configAccessor.Get<InstrumentConfig>();
             _transportConfig = configAccessor.Get<TransportConfig>();
             _skyWalkingClient = skyWalkingClient;
         }

src/SkyWalking.Core/SkyWalking.Core.csproj

@@ -16,6 +16,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="System.Diagnostics.DiagnosticSource" Version="4.5.1" />
+    <PackageReference Include="System.Memory" Version="4.5.2" />
     <PackageReference Include="System.ValueTuple" Version="4.5.0" />
   </ItemGroup>
 </Project>
\ No newline at end of file