The SQL Server transport can take advantage of native delayed delivery without the need to run the timeout manager. Instead, the transport creates dedicated infrastructure which delays messages using native SQL Server transport features.
When a message delay time lapses, SQL Server transport moves a batch of messages to the destination queue. Note that this means the exact time of delivering a delayed message is always an approximation.
From version 5 of the transport, native delayed delivery is always enabled.
Configuration
The settings described in this section have default values as shown in the snippets. The settings can be fine-tuned to fit a particular system's needs, e.g. messages are checked for expiration more frequently resulting in more accurate delivery times.
Table suffix
Delayed messages are stored in a dedicated table named endpoint-name.. The suffix is set to Delayed by default, but can be overwritten using:
delayedDeliverySettings.TableSuffix("Delayed");
Polling interval
Messages are checked for expiration every second. The polling interval can be configured using:
delayedDeliverySettings.ProcessingInterval(TimeSpan.FromSeconds(5));
Polling batch size
On each query, a batch of messages is picked and dispatched. The maximal size of the batch can be specified with:
delayedDeliverySettings.BatchSize(100);
Backwards compatibility
When upgrading to a version of the transport that supports native delayed delivery, it is safe to run a set of endpoints that include both endpoints using native delayed delivery as well as the timeout manager:
- Endpoints with native delayed delivery can send delayed messages to endpoints using the timeout manager.
- Endpoints with native delayed delivery can continue to receive delayed messages from endpoints using timeout manager.
Enable the timeout manager
To assist with the upgrade process when upgrading from an older version of the transport that doesn't support native-delayed delivery, the timeout manager can be enabled. Any delayed messages stored in the endpoint's persistence database before the upgrade are sent when their timeouts expire. Any delayed messages sent after the upgrade are sent through the native delayed delivery infrastructure, even though the timeout manager is enabled. The timeout manager migration mode can be enabled with:
delayedDeliverySettings.EnableTimeoutManagerCompatibility();
Once an endpoint has no more delayed messages in its persistence database, there is no need for the timeout manager. It can be disabled by removing the above enable call.
At this point, all . and . tables for the endpoint can be deleted from the database. In addition, the endpoint no longer requires timeout persistence, so those storage entities can be removed from the persistence database as well.