[GitHub] flink issue #2093: [FLINK-3714] Add Support for "Allowed Lateness"

[aljoscha <gi...@git.apache.org>]

Github user aljoscha commented on the issue:

    https://github.com/apache/flink/pull/2093
  
    I had some inline comments.
    
    One other thing I would like to see changed is moving the logic that checks whether to do cleanup from `cleanup()` to the call-site. So in `processElement()` it would be:
    ```
    if (combinedTriggerResult.isPurge) {
      cleanup(...);
    } else {
      registerCleanupTimer(...);
    }
    ```
    The reason for this is that the check in `cleanup()` for whether a timer is a cleanup timer does not take into account the event-time/processing-time split: if a processing-time timer fires on exactly the cleanup time of an event-time window this would also trigger cleanup.  The code in `processTriggersFor` (which, by the way can be moved back into `processWatermark()` now that you refactored this special event-time trigger hack) would have this check:
    ```
    if (assigner.isEventTime() && isCleanupTimer(...))
    ```
    while the code in `trigger()` would be
    ```
    if (!assigner.isEventTime() && isCleanupTimer(...))
    ```



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