[GitHub] [kafka] niket-goel commented on a change in pull request #11191: KAFKA-13173 Making the controller fence stale brokers one at a time if multiple stale brokers are discovered at the same time

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niket-goel commented on a change in pull request #11191:
URL: https://github.com/apache/kafka/pull/11191#discussion_r685437960



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File path: metadata/src/main/java/org/apache/kafka/controller/QuorumController.java
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@@ -858,7 +858,7 @@ private void rescheduleMaybeFenceStaleBrokers() {
             return;
         }
         scheduleDeferredWriteEvent(MAYBE_FENCE_REPLICAS, nextCheckTimeNs, () -> {
-            ControllerResult<Void> result = replicationControl.maybeFenceStaleBrokers();
+            ControllerResult<Void> result = replicationControl.maybeFenceOneStaleBroker();
             rescheduleMaybeFenceStaleBrokers();

Review comment:
       I thought about doing that, but then realized that a call to reschedule will automatically result in a scheduling of another invocation right away if there were any brokers that were deemed stale still remaining in the unfenced list.
   
   This will happen because the `nextCheckTimeNs` is based on when the broker with the older `lastContactNs` time (broker at the head of the list) would time out. This will always result in a time less than now if we have a stale broker and there should be no delay in executing this again (barring queue depth).
   
   I also did not want to "prioritize" (if that's even possible) over other requests, because my understanding is that the fix works as long as a subsequent fence broker call is made after the first has been processed by the controller thread (which would also happen by picking up the record from the queue and replaying it).
   
   Please let me know if my understanding is off here.




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