Specifies a decision made by the decider. A decision can be one of these types:
TimerCanceled
event in the history.WorkflowExecutionCanceled
event in the history.WorkflowExecutionCompleted
event in the history .WorkflowExecutionContinuedAsNew
event is recorded in the history.WorkflowExecutionFailed
event in the history.MarkerRecorded
event in the history. Markers can be used for adding custom information in the history for instance to let deciders know that they do not need to look at the history beyond the marker event.RequestCancelExternalWorkflowExecutionInitiated
event in the history.SignalExternalWorkflowExecutionInitiated
event in the history.StartChildWorkflowExecutionInitiated
event in the history. The child workflow execution is a separate workflow execution with its own history.TimerStarted
event in the history. This timer will fire after the specified delay and record a TimerFired
event.Access Control
If you grant permission to use RespondDecisionTaskCompleted
, you can use IAM policies to express permissions for the list of decisions returned by this action as if they were members of the API. Treating decisions as a pseudo API maintains a uniform conceptual model and helps keep policies readable. For details and example IAM policies, see Using IAM to Manage Access to Amazon SWF Workflows .
Decision Failure
Decisions can fail for several reasons
One of the following events might be added to the history to indicate an error. The event attribute's cause parameter indicates the cause. If cause is set to OPERATION_NOT_PERMITTED, the decision failed because it lacked sufficient permissions.
workflowID
specified in the decision was incorrect. workflowID
specified in the decision was incorrect. The preceding error events might occur due to an error in the decider logic, which might put the workflow execution in an unstable state The cause field in the event structure for the error event indicates the cause of the error.
NOTE: A workflow execution may be closed by the decider by returning one of the following decisions when completing a decision task: CompleteWorkflowExecution, FailWorkflowExecution, CancelWorkflowExecution and ContinueAsNewWorkflowExecution. An UnhandledDecision fault will be returned if a workflow closing decision is specified and a signal or activity event had been added to the history while the decision task was being performed by the decider. Unlike the above situations which are logic issues, this fault is always possible because of race conditions in a distributed system. The right action here is to call RespondDecisionTaskCompleted without any decisions. This would result in another decision task with these new events included in the history. The decider should handle the new events and may decide to close the workflow execution.
How to Code a Decision
You code a decision by first setting the decision type field to one of the above decision values, and then set the corresponding attributes field shown below: