remove the concept of the unsent queue; the pipeline **is** that queue - no...

remove the concept of the unsent queue; the pipeline **is** that queue - no need to duplicate (and significantly simplifies); if you've successfully pushed a message to the bridge: *it is in the pipe*; also removes "ar", "wr", "wq", "qu" and "pending" counters

StackExchange.Redis/StackExchange/Redis/ConnectionMultiplexer.ReaderWriter.cs

@@ -18,18 +18,6 @@ public partial class ConnectionMultiplexer
             if (ownsSocketManager) socketManager?.Dispose();
             socketManager = null;
         }
-
-        internal void RequestWrite(PhysicalBridge bridge, bool forced)
-        {
-            if (bridge == null) return;
-            var tmp = SocketManager;
-            if (tmp != null)
-            {
-                Trace("Requesting write: " + bridge.Name);
-                tmp.RequestWrite(bridge, forced);
-            }
-        }
-
         partial void OnWriterCreated();
     }
 }

StackExchange.Redis/StackExchange/Redis/ConnectionMultiplexer.cs

@@ -2007,10 +2007,6 @@ internal T ExecuteSyncImpl<T>(Message message, ResultProcessor<T> processor, Ser
                         }
                         else
                         {
-#if FEATURE_SOCKET_MODE_POLL
-                            var mgrState = socketManager.State;
-                            var lastError = socketManager.LastErrorTimeRelative();
-#endif
                             var sb = new StringBuilder("Timeout performing ").Append(message.CommandAndKey);
                             data = new List<Tuple<string, string>> { Tuple.Create("Message", message.CommandAndKey) };
                             void add(string lk, string sk, string v)
@@ -2019,20 +2015,12 @@ void add(string lk, string sk, string v)
                                 sb.Append(", ").Append(sk).Append(": ").Append(v);
                             }
 
-                            int queue = server.GetOutstandingCount(message.Command, out int inst, out int qu, out int qs, out int qc, out int wr, out int wq, out int @in, out int ar);
+                            int queue = server.GetOutstandingCount(message.Command, out int inst, out int qs, out int qc, out int @in);
                             add("Instantaneous", "inst", inst.ToString());
-#if FEATURE_SOCKET_MODE_POLL
-                            add("Manager-State", "mgr", mgrState.ToString());
-                            add("Last-Error", "err", lastError);
-#endif
                             add("Queue-Length", "queue", queue.ToString());
-                            add("Queue-Outstanding", "qu", qu.ToString());
                             add("Queue-Awaiting-Response", "qs", qs.ToString());
                             add("Queue-Completion-Outstanding", "qc", qc.ToString());
-                            add("Active-Writers", "wr", wr.ToString());
-                            add("Write-Queue", "wq", wq.ToString());
                             add("Inbound-Bytes", "in", @in.ToString());
-                            add("Active-Readers", "ar", ar.ToString());
 
                             add("Client-Name", "clientName", ClientName);
                             add("Server-Endpoint", "serverEndpoint", server.EndPoint.ToString());

StackExchange.Redis/StackExchange/Redis/DebuggingAids.cs

@@ -17,12 +17,6 @@ internal partial class ResultBox
 
     public partial interface IServer
     {
-        /// <summary>
-        /// Show what is in the pending (unsent) queue
-        /// </summary>
-        /// <param name="maxCount">The maximum count to list.</param>
-        string ListPending(int maxCount);
-
         /// <summary>
         /// Get the value of key. If the key does not exist the special value nil is returned. An error is returned if the value stored at key is not a string, because GET only handles string values.
         /// </summary>
@@ -114,21 +108,11 @@ internal void SimulateConnectionFailure()
             interactive?.SimulateConnectionFailure();
             subscription?.SimulateConnectionFailure();
         }
-
-        internal string ListPending(int maxCount)
-        {
-            var sb = new StringBuilder();
-            interactive?.ListPending(sb, maxCount);
-            subscription?.ListPending(sb, maxCount);
-            return sb.ToString();
-        }
     }
 
     internal partial class RedisServer
     {
         void IServer.SimulateConnectionFailure() => server.SimulateConnectionFailure();
-        string IServer.ListPending(int maxCount) => server.ListPending(maxCount);
-
         void IServer.Crash()
         {
             // using DB-0 because we also use "DEBUG OBJECT", which is db-centric
@@ -225,11 +209,6 @@ internal void SimulateConnectionFailure()
             }
             physical?.RecordConnectionFailed(ConnectionFailureType.SocketFailure);
         }
-
-        internal void ListPending(StringBuilder sb, int maxCount)
-        {
-            queue.ListPending(sb, maxCount);
-        }
     }
 
     internal partial class PhysicalConnection

StackExchange.Redis/StackExchange/Redis/PhysicalConnection.cs

@@ -169,14 +169,14 @@ public void RecordConnectionFailed(ConnectionFailureType failureType, ref Socket
 
             // stop anything new coming in...
             Bridge.Trace("Failed: " + failureType);
-            int @in = -1, ar = -1;
+            int @in = -1;
             managerState = SocketManager.ManagerState.RecordConnectionFailed_OnDisconnected;
             Bridge.OnDisconnected(failureType, this, out bool isCurrent, out PhysicalBridge.State oldState);
             if (oldState == PhysicalBridge.State.ConnectedEstablished)
             {
                 try
                 {
-                    @in = GetAvailableInboundBytes(out ar);
+                    @in = GetAvailableInboundBytes();
                 }
                 catch { /* best effort only */ }
             }
@@ -211,23 +211,16 @@ void add(string lk, string sk, string v)
                     add("Last-Write", "last-write", (unchecked(now - lastWrite) / 1000) + "s ago");
                     add("Unanswered-Write", "unanswered-write", (unchecked(now - unansweredRead) / 1000) + "s ago");
                     add("Keep-Alive", "keep-alive", Bridge.ServerEndPoint.WriteEverySeconds + "s");
-                    add("Pending", "pending", Bridge.GetPendingCount().ToString());
                     add("Previous-Physical-State", "state", oldState.ToString());
 
                     if (@in >= 0)
                     {
                         add("Inbound-Bytes", "in", @in.ToString());
-                        add("Active-Readers", "ar", ar.ToString());
                     }
 
                     add("Last-Heartbeat", "last-heartbeat", (lastBeat == 0 ? "never" : ((unchecked(now - lastBeat) / 1000) + "s ago")) + (Bridge.IsBeating ? " (mid-beat)" : ""));
                     add("Last-Multiplexer-Heartbeat", "last-mbeat", Multiplexer.LastHeartbeatSecondsAgo + "s ago");
                     add("Last-Global-Heartbeat", "global", ConnectionMultiplexer.LastGlobalHeartbeatSecondsAgo + "s ago");
-#if FEATURE_SOCKET_MODE_POLL
-                    var mgr = Bridge.Multiplexer.SocketManager;
-                    add("SocketManager-State", "mgr", mgr.State.ToString());
-                    add("Last-Error", "err", mgr.LastErrorTimeRelative());
-#endif
                 }
 
                 var ex = innerException == null
@@ -592,6 +585,12 @@ private static int WriteRaw(Span<byte> span, long value, bool withLengthPrefix =
             return WriteCrlf(span, offset);
         }
 
+        internal void WakeWriterAndCheckForThrottle()
+        {
+            var flush = _ioPipe.Output.FlushAsync();
+            if (!flush.IsCompletedSuccessfully) flush.AsTask().Wait();
+        }
+
         static readonly byte[] NullBulkString = Encoding.ASCII.GetBytes("$-1\r\n"), EmptyBulkString = Encoding.ASCII.GetBytes("$0\r\n\r\n");
         private static void WriteUnified(PipeWriter writer, byte[] value)
         {
@@ -802,14 +801,7 @@ private static void WriteUnified(PipeWriter writer, long value)
             writer.Advance(bytes);
         }
 
-
-        private int haveReader;
-
-        internal int GetAvailableInboundBytes(out int activeReaders)
-        {
-            activeReaders = Interlocked.CompareExchange(ref haveReader, 0, 0);
-            return socketToken.Available;
-        }
+        internal int GetAvailableInboundBytes() => socketToken.Available;
 
         private static LocalCertificateSelectionCallback GetAmbientCertificateCallback()
         {

StackExchange.Redis/StackExchange/Redis/ServerEndPoint.cs

@@ -367,15 +367,15 @@ internal ServerCounters GetCounters()
             return counters;
         }
 
-        internal int GetOutstandingCount(RedisCommand command, out int inst, out int qu, out int qs, out int qc, out int wr, out int wq, out int @in, out int ar)
+        internal int GetOutstandingCount(RedisCommand command, out int inst, out int qs, out int qc, out int @in)
         {
             var bridge = GetBridge(command, false);
             if (bridge == null)
             {
-                return inst = qu = qs = qc = wr = wq = @in = ar = 0;
+                return inst = qs = qc = @in = 0;
             }
 
-            return bridge.GetOutstandingCount(out inst, out qu, out qs, out qc, out wr, out wq, out @in, out ar);
+            return bridge.GetOutstandingCount(out inst, out qs, out qc, out @in);
         }
 
         internal string GetProfile()

StackExchange.Redis/StackExchange/Redis/SocketManager.cs

 using System;
-using System.Collections.Generic;
 using System.IO;
 using System.IO.Pipelines;
 using System.Net;
@@ -13,9 +12,7 @@ namespace StackExchange.Redis
     internal enum SocketMode
     {
         Abort,
-        [Obsolete("just don't", error: true)]
-        Poll,
-        Async
+        Async,
     }
 
     /// <summary>
@@ -109,10 +106,6 @@ internal enum ManagerState
             ProcessErrorQueue,
         }
         
-        private readonly Queue<PhysicalBridge> writeQueue = new Queue<PhysicalBridge>();
-        private bool isDisposed;
-        private readonly bool useHighPrioritySocketThreads = true;
-
         /// <summary>
         /// Gets the name of this SocketManager instance
         /// </summary>
@@ -133,11 +126,6 @@ public SocketManager(string name, bool useHighPrioritySocketThreads)
         {
             if (string.IsNullOrWhiteSpace(name)) name = GetType().Name;
             Name = name;
-            this.useHighPrioritySocketThreads = useHighPrioritySocketThreads;
-
-            _writeOneQueueAsync = () => WriteOneQueueAsync();
-
-            Task.Run(() => WriteAllQueuesAsync());
             
             const int Receive_PauseWriterThreshold = 1024 * 1024 * 1024; // let's give it up to 1GiB of buffer for now
 
@@ -159,9 +147,6 @@ public SocketManager(string name, bool useHighPrioritySocketThreads)
         readonly DedicatedThreadPoolPipeScheduler _scheduler;
         internal readonly PipeOptions SendPipeOptions, ReceivePipeOptions;
 
-        private readonly Func<Task> _writeOneQueueAsync;
-
-
         private enum CallbackOperation
         {
             Read,
@@ -174,12 +159,6 @@ private enum CallbackOperation
         public void Dispose()
         {
             _scheduler?.Dispose();
-            lock (writeQueue)
-            {
-                // make sure writer threads know to exit
-                isDisposed = true;
-                Monitor.PulseAll(writeQueue);
-            }
             OnDispose();
         }
         internal SocketToken BeginConnect(EndPoint endpoint, ISocketCallback callback, ConnectionMultiplexer multiplexer, TextWriter log)
@@ -247,27 +226,6 @@ void proxyCallback(IAsyncResult ar)
             return token;
         }
 
-
-
-        internal void RequestWrite(PhysicalBridge bridge, bool forced)
-        {
-            if (Interlocked.CompareExchange(ref bridge.inWriteQueue, 1, 0) == 0 || forced)
-            {
-                lock (writeQueue)
-                {
-                    writeQueue.Enqueue(bridge);
-                    if (writeQueue.Count == 1)
-                    {
-                        Monitor.PulseAll(writeQueue);
-                    }
-                    else if (writeQueue.Count >= 2)
-                    { // struggling are we? let's have some help dealing with the backlog
-                        Task.Run(_writeOneQueueAsync);
-                    }
-                }
-            }
-        }
-        
         internal void Shutdown(SocketToken token)
         {
             Shutdown(token.Socket);
@@ -345,88 +303,5 @@ private void Shutdown(Socket socket)
                 try { socket.Dispose(); } catch { }
             }
         }
-
-        private async Task WriteAllQueuesAsync()
-        {
-            while (true)
-            {
-                PhysicalBridge bridge;
-                lock (writeQueue)
-                {
-                    if (writeQueue.Count == 0)
-                    {
-                        if (isDisposed) break; // <========= exit point
-                        Monitor.Wait(writeQueue);
-                        if (isDisposed) break; // (woken by Dispose)
-                        if (writeQueue.Count == 0) continue; // still nothing...
-                    }
-                    bridge = writeQueue.Dequeue();
-                }
-
-                switch (await bridge.WriteQueueAsync(200))
-                {
-                    case WriteResult.MoreWork:
-                    case WriteResult.QueueEmptyAfterWrite:
-                        // back of the line!
-                        lock (writeQueue)
-                        {
-                            writeQueue.Enqueue(bridge);
-                        }
-                        break;
-                    case WriteResult.CompetingWriter:
-                        break;
-                    case WriteResult.NoConnection:
-                        Interlocked.Exchange(ref bridge.inWriteQueue, 0);
-                        break;
-                    case WriteResult.NothingToDo:
-                        if (!bridge.ConfirmRemoveFromWriteQueue())
-                        { // more snuck in; back of the line!
-                            lock (writeQueue)
-                            {
-                                writeQueue.Enqueue(bridge);
-                            }
-                        }
-                        break;
-                }
-            }
-        }
-
-        private Task WriteOneQueueAsync()
-        {
-            PhysicalBridge bridge;
-            lock (writeQueue)
-            {
-                bridge = writeQueue.Count == 0 ? null : writeQueue.Dequeue();
-            }
-            if (bridge == null) return Task.CompletedTask;
-            return WriteOneQueueAsyncImpl(bridge);
-        }
-        private async Task WriteOneQueueAsyncImpl(PhysicalBridge bridge)
-        {
-            bool keepGoing;
-            do
-            {
-                switch (await bridge.WriteQueueAsync(-1))
-                {
-                    case WriteResult.MoreWork:
-                    case WriteResult.QueueEmptyAfterWrite:
-                        keepGoing = true;
-                        break;
-                    case WriteResult.NothingToDo:
-                        keepGoing = !bridge.ConfirmRemoveFromWriteQueue();
-                        break;
-                    case WriteResult.CompetingWriter:
-                        keepGoing = false;
-                        break;
-                    case WriteResult.NoConnection:
-                        Interlocked.Exchange(ref bridge.inWriteQueue, 0);
-                        keepGoing = false;
-                        break;
-                    default:
-                        keepGoing = false;
-                        break;
-                }
-            } while (keepGoing);
-        }
     }
 }