Connection settings

Component: RabbitMQ Transport
NuGet NServiceBus.RabbitMQ (4.x)
Target NServiceBus Version: 6.x

RabbitMQ uses the AMQP URI Specification. The RabbitMQ transport requires a connection string to connect to the RabbitMQ broker. This connection string can be specified via code or via app.config.

Specifying the connection string via code

To specify the connection string in code:

var transport = endpointConfiguration.UseTransport<RabbitMQTransport>();
transport.ConnectionString("My custom connection string");

Specifying the connection string via app.config

By default, the transport will look for a connection string called NServiceBus/Transport in app.config:

<connectionStrings>
  <add name="NServiceBus/Transport"
       connectionString="host=broker1"/>
</connectionStrings>

To use a custom name for the connection string:

var transport = endpointConfiguration.UseTransport<RabbitMQTransport>();
transport.ConnectionStringName("MyConnectionStringName");

Connection string options

Below is the list of connection string options. When constructing a connection string, these options should be separated by a semicolon.

Host

The host name of the broker.

This Host value is required.

By default, the guest user can only connect via localhost. If connecting to a remote host, a user name and password must be provided.

<connectionStrings>
   <add name="NServiceBus/Transport"
        connectionString="host=myremoteserver;
                          username=myusername;
                          password=mypassword"/>
</connectionStrings>

Port

The port where the broker listens.

Default: 5671 if the UseTls setting is set to true, otherwise the default value is 5672

VirtualHost

The virtual host to use.

Default: /

UserName

The user name to use to connect to the broker.

Default: guest

Password

The password to use to connect to the broker.

Default: guest

RequestedHeartbeat

The interval for the heartbeats between the client and the server.

Default: 5 seconds

RetryDelay

The time to wait before trying to reconnect to the broker if the connection is lost.

Default: 10 seconds

UseTls

Indicates if the connection to the broker should be secured with TLS.

Default: false

CertPath

The file path to the client authentication certificate when using TLS.

CertPassphrase

The password for the client authentication certificate specified in CertPath

For debugging purposes, it can be helpful to increase the RequestedHeartbeat setting as shown below:
<connectionStrings>
  <add name="NServiceBus/Transport"
       connectionString="host=broker1;RequestedHeartbeat=600"/>
</connectionStrings>

Increasing this setting can help prevent the connection to the broker from timing out while the code is paused from hitting a breakpoint.

Transport Layer Security support

Secure connections to the broker using Transport Layer Security (TLS) are supported. To enable TLS support, set the UseTls setting to true in the connection string. If the broker has been configured to require client authentication, a client certificate must be specified in the CertPath setting. If that certificate requires a password, it must be specified in the CertPassphrase setting.

An example connection string using these settings:

host=broker1;UseTls=true;CertPath=C:\CertificatePath\ssl.pfx;CertPassphrase=securePassword

In Versions 4.3 and above, client certificates can be specified via code instead of using CertPath and CertPassphrase:

var transport = endpointConfiguration.UseTransport<RabbitMQTransport>();
transport.SetClientCertificates(new X509CertificateCollection());
If a certificate is specified via the code API, the CertPath and CertPassphrase connection string settings are ignored.
TLS 1.2 must be enabled on the broker to establish a secure connection.

Controlling the prefetch count

When consuming messages from the broker, throughput can be improved by having the consumer prefetch additional messages. The prefetch count is calculated by setting it to a multiple of the maximum concurrency value. The multiplier in the calculation is set to 3 by default, but it can be changed by using the following:

var transport = endpointConfiguration.UseTransport<RabbitMQTransport>();
transport.PrefetchMultiplier(4);

Alternatively, the calculation can be overridden by setting the prefetch count directly using the following:

var transport = endpointConfiguration.UseTransport<RabbitMQTransport>();
transport.PrefetchCount(100);
If the configured value is less than the maximum concurrency, the prefetch count will be set to the maximum concurrency value instead.

Publisher confirms

Publisher confirms are enabled by default, but they can be disabled by using the following:

var transport = endpointConfiguration.UseTransport<RabbitMQTransport>();
transport.UsePublisherConfirms(false);

Controlling behavior when the broker connection is lost

The RabbitMQ transport monitors the connection to the broker and will trigger the critical error action if the connection fails and stays disconnected for the configured amount of time.

TimeToWaitBeforeTriggering

Controls the amount of time the transport waits after a failure is detected before triggering the critical error action.

Type: System.TimeSpan

Default: 00:02:00 (2 minutes)

var transport = endpointConfiguration.UseTransport<RabbitMQTransport>();
transport.TimeToWaitBeforeTriggeringCircuitBreaker(TimeSpan.FromMinutes(2));

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