Does PurgeInstanceHistoryAsync remove old history for infinite orchestrations that use ContinueAsNew

user_3152458 0
Viewed 524

I have an orchestration that runs as a singleton by using the same instance id each time. It also runs infinitely by using ContinueAsNew at the end of each iteration to keep the history manageable. However, I have noticed that the history of each past iteration is kept in the history table, each with a different execution id (as is expected when ContinueAsNew is called).

I also use PurgeInstanceHistoryAsync once a day to delete any completed, failed, terminated or cancelled orchestrations that are more than 14 days old. However, since the infinite singleton orchestration is never in any of these states will PurgeInstanceHistoryAsync ever clean up the old execution histories?

The same question can be asked for a periodic singleton orchestration (i.e. an orchestration that runs periodically but uses the same instance Id each time). If the purge process happens whilst the orchestration is running, will any old histories be removed, or would it be a matter of luck that the orchestration is not actually running at the time the purge executes?

azure-durable-functions
1 Answers

If you look in your history table in the azure storage account and query for your instance you should see that using ContinueAsNew will actually purge history automatically. (In my test it seemed to be at most 1 execution behind.)

From Docs: https://docs.microsoft.com/sv-se/azure/azure-functions/durable/durable-functions-eternal-orchestrations?tabs=csharp#resetting-and-restarting

When ContinueAsNew is called, the instance enqueues a message to itself before it exits. The message restarts the instance with the new input value. The same instance ID is kept, but the orchestrator function's history is effectively truncated.

user_97428890
Related