[GitHub] [helix] jiajunwang commented on a change in pull request #1650: Improve auto enter maintenance mode

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

jiajunwang commented on a change in pull request #1650:
URL: https://github.com/apache/helix/pull/1650#discussion_r577838791



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File path: helix-core/src/main/java/org/apache/helix/controller/stages/BestPossibleStateCalcStage.java
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@@ -193,15 +193,19 @@ public Object call() {
   }
 
   // Check whether the offline/disabled instance count in the cluster reaches the set limit,
-  // if yes, pause the rebalancer, and throw exception to terminate rebalance cycle.
+  // if yes, auto enable maintenance mode, and use the maintenance rebalancer for this pipeline.
   private boolean validateOfflineInstancesLimit(final ResourceControllerDataProvider cache,
       final HelixManager manager) {
     int maxOfflineInstancesAllowed = cache.getClusterConfig().getMaxOfflineInstancesAllowed();
     if (maxOfflineInstancesAllowed >= 0) {
       int offlineCount = cache.getAllInstances().size() - cache.getEnabledLiveInstances().size();
       if (offlineCount > maxOfflineInstancesAllowed) {
+        // Enable maintenance mode in cache so the maintenance rebalancer is used for this pipeline
+        cache.enableMaintenanceMode();

Review comment:
       IMO, we should ensure the ZK update is done before enable it in the cache. This will help to prevent multiple potential consistency issues.




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