Auditing Messages

Component: NServiceBus
NuGet Package NServiceBus (6.x)

The distributed nature of parallel, message-driven systems makes them more difficult to debug than their sequential, synchronous and centralized counterparts. For these reasons, NServiceBus provides built-in message auditing for every endpoint. Configure NServiceBus to audit and it will capture a copy of every received message and forward it to a specified audit queue.

By default, auditing is not enabled and must be configured for each endpoint where auditing is required.

It is recommended to specify a central auditing queue for all related endpoints (i.e. endpoints that belong to the same system). This gives an overview of the entire system in one place and can help see how messages correlate. One can look at the audit queue as a central record of everything that is happening in the system. A central audit queue is also required by the Particular Service Platform and especially ServiceControl, which consumes messages from these auditing queues. For more information, see ServicePulse documentation.

Message headers

The audited message is enriched with additional headers, which contain information related to processing the message:

  • Processing start and end times.
  • Processing host id and name.
  • Processing machine address.
  • Processing endpoint.

Handling Audit messages

Audit messages can be handled in a variety of ways: Save them in a database, do custom logging, etc. It is important not to leave the messages in the audit queue however, as most queuing technologies have upper-bound limits on their queue sizes and depth. By not processing these messages, the limits of the underlying queue technology may be reached.

Audit configuration options

There two settings that control auditing:

Queue Name

The queue name to forward audit messages to

OverrideTimeToBeReceived

To force a TimeToBeReceived on audit messages by setting OverrideTimeToBeReceived use the configuration syntax below.

Note that while the phrasing is "forwarding a message" in the implementation it is actually "cloning and sending a new message". This is important when considering TimeToBeReceived since the time taken to receive and process the original message is not part of the TimeToBeReceived of the new audit message. In effect the audit message receives the full time allotment of whatever TimeToBeReceived is used.

MSMQ forces the same TimeToBeReceived on all messages in a transaction. Therefore, OverrideTimeToBeReceived is not supported when using the MSMQ Transport. If OverrideTimeToBeReceived is detected when using MSMQ an exception will be thrown with the following text:

Setting a custom OverrideTimeToBeReceived for audits is not supported on transactional MSMQ

Default Value

If no OverrideTimeToBeReceived is defined then:

Versions 5 and below: TimeToBeReceived of the original message will be used.

Versions 6 and above: No TimeToBeReceived will be set.

Configuring auditing

Using Code

Configure the target audit queue using the configuration API.

endpointConfiguration.AuditProcessedMessagesTo("targetAuditQueue");

Using app.config

Configuring this feature via app.config, IConfigurationProvider, or IProvideConfiguration is deprecated in Version 7.
<configuration>
  <configSections>
    <section name="AuditConfig"
             type="NServiceBus.Config.AuditConfig, NServiceBus.Core"/>
  </configSections>
  <AuditConfig QueueName="targetAuditQueue"
               OverrideTimeToBeReceived="00:10:00"/>
</configuration>
OverrideTimeToBeReceived needs to be a valid TimeSpan.

Using IProvideConfiguration

The audit settings can also be configured using code via a custom configuration provider.

class ProvideConfiguration :
    IProvideConfiguration<AuditConfig>
{
    public AuditConfig GetConfiguration()
    {
        return new AuditConfig
        {
            QueueName = "targetAuditQueue",
            OverrideTimeToBeReceived = TimeSpan.FromMinutes(10)
        };
    }
}

Machine level configuration

Versions 4 and above support setting the error queue and the audit queue at the machine level in the registry. Use the Set-NServiceBusLocalMachineSettings PowerShell commandlet to set these values at a machine level. When set at machine level, the setting is not required in the endpoint configuration file for messages to be forwarded to the audit queue.

Turning off auditing

If the auditing settings are in app.config, remove them or comment them out.

If the machine level auditing is turned on, clear the value for the string value AuditQueue under

HKEY_LOCAL_MACHINE\SOFTWARE\ParticularSoftware\ServiceBus

If running 64 bit, in addition to the above, also clear the value for AuditQueue under

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\ParticularSoftware\ServiceBus

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