[GitHub] [kafka] mumrah commented on pull request #13742: KAFKA-14996: Handle overly large user operations on the kcontroller

["mumrah (via GitHub)" <gi...@apache.org>]

mumrah commented on PR #13742:
URL: https://github.com/apache/kafka/pull/13742#issuecomment-1564483362

   @divijvaidya Colin can correct me if I'm mistaken, but I believe this patch is mainly about closing an existing edge case until we implement KIP-868 (metadata transactions). Once we have transactions in the controller, we can allow arbitrarily large batches of records.
   
   > I am concerned about the user facing aspect of this change. If I am a user and get this exception, what am I expected to do to resolve it?
   
   Right now, if you create a topic with more than ~10000 partitions, you'll get a server error anyways. The controller fails to commit the batch, throws and exception, and the renounces leadership. 
   
   Here's what happens on the controller:
   ```
   [2023-05-26 10:24:28,308] DEBUG [QuorumController id=1] Got exception while running createTopics(1813420413). Invoking handleException. (org.apache.kafka.queue.KafkaEventQueue)
   java.lang.IllegalStateException: Attempted to atomically commit 20001 records, but maxRecordsPerBatch is 10000
   	at org.apache.kafka.controller.QuorumController.appendRecords(QuorumController.java:812)
   	at org.apache.kafka.controller.QuorumController$ControllerWriteEvent.run(QuorumController.java:719)
   	at org.apache.kafka.queue.KafkaEventQueue$EventContext.run(KafkaEventQueue.java:127)
   	at org.apache.kafka.queue.KafkaEventQueue$EventHandler.handleEvents(KafkaEventQueue.java:210)
   	at org.apache.kafka.queue.KafkaEventQueue$EventHandler.run(KafkaEventQueue.java:181)
   	at java.lang.Thread.run(Thread.java:750)
   [2023-05-26 10:24:28,314] INFO [RaftManager id=1] Received user request to resign from the current epoch 3 (org.apache.kafka.raft.KafkaRaftClient)
   [2023-05-26 10:24:28,323] INFO [RaftManager id=1] Failed to handle fetch from 2 at 142 due to NOT_LEADER_OR_FOLLOWER (org.apache.kafka.raft.KafkaRaftClient)
   ```
   
   And the client sees:
   ```
   [2023-05-26 10:24:28,351] ERROR org.apache.kafka.common.errors.UnknownServerException: The server experienced an unexpected error when processing the request.
    (kafka.admin.TopicCommand$)
   ```
   
   So, really this patch isn't changing anything from the client's perspective. It's just prevent the controller from renouncing (which is the real problem).


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