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# MongoDB

MongoDB is a cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with schema.

CAP has supported MongoDB as persistent since version 2.3 .

MongoDB supports ACID transactions since version 4.0, so CAP only supports MongoDB above 4.0, and MongoDB needs to be deployed as a cluster, because MongoDB's ACID transaction requires a cluster to be used.

For a quick development of the MongoDB 4.0+ cluster for the development environment, you can refer to this article.

## Configuration

To use MongoDB storage, you need to install the following extensions from NuGet:

    PM> Install-Package DotNetCore.CAP.MongoDB

Next, add configuration items to the `ConfigureServices` method of `Startup.cs`.

    public void ConfigureServices(IServiceCollection services)
    {
        // ...

        services.AddCap(x =>
        {
            x.UseMongoDB(opt=>{
                //MongoDBOptions
            });
            // x.UseXXX ...
        });
    }

#### MongoDB Options

NAME | DESCRIPTION | TYPE | DEFAULT
--- | --- | --- | ---
DatabaseName | Database name | string | cap
DatabaseConnection | Database connection string | string | mongodb://localhost:27017
ReceivedCollection | Database received message collection name | string | cap.received
PublishedCollection | Database published message collection name | string | cap.published

## Publish with transaction

The following example shows how to leverage CAP and MongoDB for local transaction integration.

    //NOTE: Before your test, your need to create database and collection at first.
    //      Mongo can't create databases and collections in transactions automatic,
    //      so you need to create them separately, simulating a record insert
    //      will automatically create.

    // var mycollection = _client.GetDatabase("test")
    //          .GetCollection<BsonDocument>("test.collection");
    // mycollection.InsertOne(new BsonDocument { { "test", "test" } });

    using (var session = _client.StartTransaction(_capBus, autoCommit: false))
    {
        var collection = _client.GetDatabase("test")
                .GetCollection<BsonDocument>("test.collection");

        collection.InsertOne(session, new BsonDocument { { "hello", "world" } });

        _capBus.Publish("sample.rabbitmq.mongodb", DateTime.Now);

        session.CommitTransaction();
    }