[jira] [Created] (KAFKA-6015) NPE in RecordAccumulator

["Apurva Mehta (JIRA)" <ji...@apache.org>]

Apurva Mehta created KAFKA-6015:
-----------------------------------

             Summary: NPE in RecordAccumulator
                 Key: KAFKA-6015
                 URL: https://issues.apache.org/jira/browse/KAFKA-6015
             Project: Kafka
          Issue Type: Bug
    Affects Versions: 1.0.0
            Reporter: Apurva Mehta
            Assignee: Apurva Mehta
            Priority: Blocker
             Fix For: 1.0.0


I found this inadvertently while trying to create a system test to reproduce  KAFKA-6003

{noformat}java.lang.NullPointerException
        at org.apache.kafka.clients.producer.internals.RecordAccumulator.drain(RecordAccumulator.java:542)
        at org.apache.kafka.clients.producer.internals.Sender.sendProducerData(Sender.java:270)
        at org.apache.kafka.clients.producer.internals.Sender.run(Sender.java:238)
        at org.apache.kafka.clients.producer.internals.Sender.run(Sender.java:163)
        at java.lang.Thread.run(Thread.java:748)
{noformat}

The problem is with this line

{code:java}
if (first.hasSequence() && first.baseSequence() != transactionManager.nextBatchBySequence(first.topicPartition).baseSequence())
{code}

It is possible for the producer state to be reset (for instance if retries are expired), in which case the transaction manager will drop the in flight batches it is tracking. However, these batches will continue to be in the accumulator with a sequence, causing an NPE in the background thread on this line.

It would be better to drain the batches with the old Pid/Sequence in this case. Either they are accepted, or they will be returned to the user with an {{OutOfOrderSequenceException}} which is clearer.




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