[GitHub] [kafka] efeg commented on a change in pull request #8579: KAFKA-9930: Prevent ReplicaFetcherThread from throwing UnknownTopicOrPartitionException upon topic creation and deletion.

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efeg commented on a change in pull request #8579:
URL: https://github.com/apache/kafka/pull/8579#discussion_r419833344



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File path: core/src/main/scala/kafka/server/AbstractFetcherThread.scala
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@@ -382,6 +382,11 @@ abstract class AbstractFetcherThread(name: String,
                     "that the partition is being moved")
                   partitionsWithError += topicPartition
 
+                case Errors.UNKNOWN_TOPIC_OR_PARTITION =>
+                  warn(s"Remote broker does not host the partition $topicPartition, which could indicate " +
+                    "that the partition is being created or deleted.")

Review comment:
       @ijuma Thanks for your reply!
   We both agree that relying on warnings in logs to _detect_ propagation issues is not practical -- metrics indeed should be used in "detection" of such issues.
   I believe the focus of this discussion isthe _investigation_ of detected issues.
   
   Metrics typically fail to provide the level of details to examine the interaction of various events in a distributed environment. Hence, in case we need to look at the logs for figuring out such cases, I claim that being able to grep warns and see undesired events is useful -- as opposed to trying to browse info logs for bad/undesirable events.
   
   Note that in `trunk`, such `UNKNOWN_TOPIC_OR_PARTITION` events are already printed in a stronger level (i.e. `error`). 




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