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What is an Activity Execution?

An Activity Execution is the full chain of Activity Task Executions.

Activity Execution

By default, an Activity Execution has no time limit. Activity Execution timeouts and retry policies can be customized.

If an Activity Execution fails (because it exhausted all retries, threw a non-retryable error, or was canceled), the error is returned to the Workflow, which decides how to handle it.

Cancellation​

Activity Cancellation:

  • lets the Activity know it doesn't need to keep doing work, and
  • gives the Activity time to clean up any resources it has created.

Activities can only receive Cancellation if they emit Heartbeats or in Core-based SDKs (TypeScript/Python) are Local Activities (which don't heartbeat but receive Cancellation anyway).

An Activity may receive Cancellation if:

  • The Activity was requested to be Cancelled. This can often cascade from Workflow Cancellation, but not always—SDKs have ways to stop Cancellation from cascading.
  • The Activity was considered failed by the Server because any of the Activity timeouts have triggered (for example, the Server didn't receive a heartbeat within the Activity's Heartbeat timeout). The Cancelled Failure that the Activity receives will have message: 'TIMED_OUT'.
  • The Workflow Run reached a Closed state, in which case the Cancelled Failure will have message: 'NOT_FOUND'.
  • In some SDKs:
    • The Worker is shutting down.
    • An Activity sends a Heartbeat but the Heartbeat details can't be converted by the Worker's configured Data Converter. This fails the Activity Task Execution with an Application Failure.

There are different ways to receive Cancellation depending on the SDK. An Activity may accept or ignore Cancellation:

  • To allow Cancellation to happen, let the Cancellation Failure propagate.
  • To ignore Cancellation, catch it and continue executing.

Some SDKs have ways to shield tasks from being stopped while still letting the Cancellation propagate.

The Workflow can also decide if it wants to wait for the Activity Cancellation to be accepted or to proceed without waiting.

Cancellation can only be requested a single time. If you try to cancel your Activity Execution more than once, it will not receive more than one Cancellation request.