Outbox with NHibernate persistence

Component: NHibernate Persistence
NuGet Package NServiceBus.NHibernate (6.x)
Target NServiceBus Version: 5.x
Standard support for version 5.x of NServiceBus has expired. For more information see our Support Policy.

The outbox feature requires persistence in order to store the messages and enable deduplication.


To keep track of duplicate messages, the NHibernate implementation of outbox requires the creation of OutboxRecord table.

Deduplication record lifespan

The NHibernate implementation by default keeps deduplication records for 7 days and runs the purge every minute.

The default settings can be changed by specifying new defaults in the config file using TimeStamp strings:

  <add key="NServiceBus/Outbox/NHibernate/TimeToKeepDeduplicationData"
       value="7.00:00:00" />
  <add key="NServiceBus/Outbox/NHibernate/FrequencyToRunDeduplicationDataCleanup"
       value="00:01:00" />

By specifying a value of -00:00:00.001 (i.e. 1 millisecond, the value of Timeout.InfiniteTimeSpan) for the NServiceBus/Outbox/NHibernate/FrequencyToRunDeduplicationDataCleanup appSetting, the cleanup task is disabled. This can be useful when an endpoint is scaled out and instances are competing to run the cleanup task.

It is advised to run the cleanup task on only one NServiceBus endpoint instance per database. Disable the cleanup task on all other NServiceBus endpoint instances for the most efficient cleanup execution.

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