[GitHub] jberstler commented on issue #271: Handle Action Error

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jberstler commented on issue #271: Handle Action Error
URL: https://github.com/apache/incubator-openwhisk-package-kafka/issues/271#issuecomment-398187924
 
 
   @regmebaby Right now, whoever fires the trigger actually gets no feedback at all about whether any connected actions even run, let alone if those actions succeed. This is as-designed to keep trigger firing as lightweight and quick as possible. As such, the kafka/message hub event provider can't automatically know that your actions failed and to skip backwards to re-fire triggers for those messages.
   
   On top of that, as far as I know, it is currently not possible to pause an event provider to stop if from firing triggers. But even if that were possible, there is also no way to tell the Kafka/Message Hub trigger to rewind and re-fire for a specific message or offset.
   
   So... what to do in this situation? If you need to guarantee that every message is processed, I think you will need to handle it in your action.
   
   One way to handle this situation is to persist somewhere (Cloudant? Reddis?) information about the messages that failed processing. You could persist either the entire message contents or, perhaps, just the topic and offset for the message as this is contained in the trigger payload sent to the action handling the messages. In either case, you could then have a periodic trigger that fires every so often to retry processing on messages that need it. This trigger would fire an action that:
   
   1. Examines your persisted store of messages that failed processing
   2. Attempts to process them by invoking the right action(s)
   3. If successful, removes the message from the store (or marks it as being successfully processed)
   4. If processing fails, it leaves those messages around for another retry, the next time the periodic trigger fires.
   
   > Should all affected messages be sent to a Dead-Letter-Queue/Topic?
   
   I believe this has been discussed at some point, but only for scenarios where the trigger fails to fire. There is no way to make the event provider do this for you when trigger successfully fires, but the triggered actions fail.
   
   I hope this helps.

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