SignalWithStartWorkflow - racy with this pattern?

Community Support
1

I’m wondering whether this pattern is safe to use as a target for SignalWithStartWorkflow:

func (wf *MyWorkflow) ControlLoop(ctx workflow.Context, someID string) (err error) {
	for {
		evt := wf.pollLastEvent(ctx)
		if evt == nil {
			break  // *** HERE
		}

		err = workflow.ExecuteChildWorkflow(
		    /* launch a handler workflow - the point of this is to serialise signal processing */
                ) // etc
	}
        // nothing left to do, so quit the workflow
	return err
}

I think the issue here is that this control loop can poll and discover no signals pending (the // HERE) and proceed to exit - as another signal arrives for processing. The workflow is “already running” so we see a warning: “Workflow has unhandled signals”

I’ve seen claims elsewhere that the above pattern is safe and that the workflow should be restarted; but I can’t find any solid documentation on this, and that doesn’t jibe with my observations. (The motivation for the above pattern was primarily to not have a bazillion idle workflows knocking around in a UI.)

Would appreciate a definitive answer “this is supposed to work” or “that is not guaranteed to work, don’t do it” so we can make some progress with this.

2

What is the code for the pollLastEvent?

3

Apologies - just grabs the associated channel (there’s one) and calls ReceiveAsync on it.
The original intention was to drain down a channel, then have the workflow quit.

4

Then, I believe this code shouldn’t lose signals.