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What is a Start-To-Close Timeout?

A Start-To-Close Timeout is the maximum time allowed for a single Activity Task Execution.

The default Start-To-Close Timeout is the same as the default Schedule-To-Close Timeout.

An Activity Execution must have either this timeout (Start-To-Close) or the Schedule-To-Close Timeout set. We recommend always setting this timeout; however, make sure that it is always set to be longer than the maximum possible time for the Activity Execution to take place. For long running Activity Executions, we recommend also using Activity Heartbeats and Heartbeat Timeouts.

The main use case for the Start-To-Close timeout is to detect when a Worker crashes after it has started executing an Activity Task.

Start-To-Close Timeout period

A Retry Policy attached to an Activity Execution retries an Activity Task Execution. Thus, the Start-To-Close Timeout is applied to each Activity Task Execution within an Activity Execution.

If the first Activity Task Execution returns an error the first time, then the full Activity Execution might look like this:

Start-To-Close Timeout period with retries

If this timeout is reached, the following actions occur:

  • An ActivityTaskTimedOut Event is written to the Workflow Execution's mutable state.
  • If a Retry Policy dictates a retry, the Temporal Cluster schedules another Activity Task.
    • The attempt count increments by 1 in the Workflow Execution's mutable state.
    • The Start-To-Close Timeout timer is reset.