[GitHub] [helix] dasahcc commented on a change in pull request #1698: Fix unexpected result when resuming a cluster from paused/maintenance mode.

[GitBox <gi...@apache.org>]

dasahcc commented on a change in pull request #1698:
URL: https://github.com/apache/helix/pull/1698#discussion_r614362946



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File path: helix-core/src/main/java/org/apache/helix/controller/GenericHelixController.java
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@@ -1469,35 +1463,41 @@ private void shutdownPipeline(Thread thread, ClusterEventBlockingQueue queue)
     }
   }
 
-  private boolean updateControllerState(NotificationContext changeContext, PauseSignal signal,
-      boolean statusFlag) {
+  private boolean updateControllerState(PauseSignal signal, boolean statusFlag) {
     if (signal != null) {
-      // This logic is used for recording first time entering PAUSE/MAINTENCE mode
       if (!statusFlag) {
         statusFlag = true;
+        // This log is recorded for the first time entering PAUSE/MAINTENANCE mode
         logger.info(String.format("controller is now %s",
             (signal instanceof MaintenanceSignal) ? "in maintenance mode" : "paused"));
       }
     } else {
-      if (statusFlag) {
-        statusFlag = false;
-        logger.info("controller is now resumed from paused state");
-        String uid = UUID.randomUUID().toString().substring(0, 8);
-        ClusterEvent event = new ClusterEvent(_clusterName, ClusterEventType.Resume,
-            String.format("%s_%s", uid, Pipeline.Type.DEFAULT.name()));
-        event.addAttribute(AttributeName.EVENT_SESSION.name(),
-            changeContext.getManager().getSessionIdIfLead());
-        event.addAttribute(AttributeName.changeContext.name(), changeContext);
-        event.addAttribute(AttributeName.helixmanager.name(), changeContext.getManager());
-        event.addAttribute(AttributeName.AsyncFIFOWorkerPool.name(), _asyncFIFOWorkerPool);
-        enqueueEvent(_eventQueue, event);
-        enqueueEvent(_taskEventQueue,
-            event.clone(String.format("%s_%s", uid, Pipeline.Type.TASK.name())));
-      }
+      statusFlag = false;
     }
     return statusFlag;
   }
 
+  /**
+   * Trigger a Resume Event if the cluster is back to activated.
+   * @param changeContext
+   * @param prevPaused the previous paused status.
+   * @param prevInMaintenanceMode the previous in maintenance mode status.
+   */
+  private void triggerResumeEvent(NotificationContext changeContext, boolean prevPaused,
+      boolean prevInMaintenanceMode) {
+    /**
+     * WARNING: the logic here is tricky.
+     * 1. Only resume if not paused. So if the Maintenance mode is removed but the cluster is still
+     * paused, the resume event should not be sent.
+     * 2. Only send resume event if the status is changed back to active. So we don't send multiple
+     * event unnecessarily.
+     */
+    if (!_paused && (prevPaused || (prevInMaintenanceMode && !_inMaintenanceMode))) {

Review comment:
       Could this check let first event missed when leaderswitch? Because when leaderswitch, prevPaused is false and current paused is false as well.




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