[GitHub] [beam] kennknowles commented on a change in pull request #13032: [BEAM-11034] Avoid build-up of stateful garbage collection timers for…

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kennknowles commented on a change in pull request #13032:
URL: https://github.com/apache/beam/pull/13032#discussion_r503400133



##########
File path: runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/SimpleParDoFn.java
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@@ -486,14 +487,23 @@ private void processTimers(
     for (W window : windowsToCleanup) {
       // The stepContext is the thing that know if it is batch or streaming, hence
       // whether state needs to be cleaned up or will simply be discarded so the
-      // timer can be ignored
-
+      // timer can be ignored.
       Instant cleanupTime = earliestAllowableCleanupTime(window, windowingStrategy);
-      // if DoFn has OnWindowExpiration then set holds for system timer.
-      Instant cleanupOutputTimestamp =
-          fnSignature.onWindowExpiration() == null ? cleanupTime : cleanupTime.minus(1L);
-      stepContext.setStateCleanupTimer(
-          CLEANUP_TIMER_ID, window, windowCoder, cleanupTime, cleanupOutputTimestamp);
+      // Set a cleanup timer for state at the end of the window to trigger onWindowExpiration and
+      // garbage collect state. We avoid doing this for the global window if there is no window
+      // expiration set as the state will be up when the pipeline terminates. Setting the timer
+      // leads to a unbounded growth of timers for pipelines with many unique keys in the global
+      // window.
+      if (cleanupTime.isBefore(GlobalWindow.INSTANCE.maxTimestamp())

Review comment:
       Re-reading the bug and thinking about your comments, can we eliminate this condition and invoke from some `onDrain` method?




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