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Worker Shutdown Behavior

When a Worker shuts down, it stops polling for new tasks and begins the shutdown sequence. In the case of in-flight Workflow Tasks, shutdown may cause them to fail if they aren’t completed in time, after exhausting Retry Policy attempts.

There are two types of shutdown behavior that can occur, depending on whether an idea of “graceful shutdown” is configured.

Graceful Shutdown​

Graceful shutdown configures how much time a Worker has to complete its current task before shutting down. An Activity is able to determine that the Worker it’s running on is being shut down, through the Activity context.

Core SDKs - graceful_shutdown_period

Go - WorkerStopTimeout

Java - shutdown() followed by awaitTermination(timeout, unit)

Workflow tasks​

Any in-flight Workflow Tasks are (attempted to be) completed. The only reason they may not immediately, is if Workflow code is (incorrectly) blocking, or because of Local Activities (see below).

Activities​

Activities are allowed to complete during the graceful shutdown period.

Local Activities​

Because Local Activities run within a Workflow Task, current and future Local Activities within the same Workflow Task will be allowed to run and complete, assuming there is no additional command to yield to.

If the Local Activity is unable to complete by the graceful shutdown period, the Local Activity attempt is sent a cancel signal. In this case, no new Local Activities will be retried or started, and the Worker is shut down. The Worker still waits for the current Workflow Task to complete, meaning you can eventually hit your Workflow Task or execution timeout, unless another Worker is spun up.

Non-Graceful Period Shutdown​

This behavior is for either no graceful period being specified, or if the shutdown has taken longer than the configured graceful period. In all cases, the Activity context is canceled and the Worker will finish shutdown when the current Workflow Task completes (with either success or failure).

note

Go and Core SDKs behave differently when we pass task timeout and the Activity or Local Activity is still running:

Go - The shutdown completes, but the Activity will continue to run and use a slot.

Core - The Worker shutdown will not complete while the Activity completes.

Local Activities​

The Local Activity is sent a cancel signal, then the Workflow Task heartbeats stop, and no new Local Activities will be retried or started. The Worker still waits for the current Workflow Task to complete, meaning you can eventually hit your Workflow Task or execution timeout, unless another Worker is spun up.

General Developer Guidance​

  • Ensure Activities and Local Activities honor context cancellation or other shutdown signals.
  • Expect that long or hung Local Activities may block shutdown unless you fail early. It is recommended that Local Activities should already generally be used for short Activities.