The Outbox feature requires persistence in order to store messages and enable deduplication.
Extra collections created by the RavenDB Outbox persistence
To keep track of duplicate messages, the RavenDB implementation of Outbox creates a special collection of documents called OutboxRecord.
Deduplication record lifespan
The RavenDB implementation by default keeps deduplication records for 7 days and runs the purge every 1 minute.
These default settings can be changed by specifying new defaults in the settings dictionary:
var outbox = endpointConfiguration.EnableOutbox();
outbox.SetTimeToKeepDeduplicationData(TimeSpan.FromDays(7));
outbox.SetFrequencyToRunDeduplicationDataCleanup(TimeSpan.FromMinutes(1));
Starting with NServiceBus.RavenDB version 6.3, it is recommended to disable cleanup and rely on document expiration instead.
Cleanup may be disabled by specifying Timeout. for SetFrequencyToRunDeduplicationDataCleanup:
var outbox = endpointConfiguration.EnableOutbox();
outbox.SetFrequencyToRunDeduplicationDataCleanup(Timeout.InfiniteTimeSpan);
If document expiration cannot be used, to improve efficiency it is advised to run cleanup on only one endpoint instance per RavenDB database, by disabling clean up on all other endpoint instances.