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Date: Wed, 25 Oct 2017 21:16:03 +0000 (UTC)
From: "Ismael Juma (JIRA)" <jira@apache.org>
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Subject: [jira] [Updated] (KAFKA-6119) Silent Data Loss in Kafka011
 Transactional Producer
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archived-at: Wed, 25 Oct 2017 21:16:13 -0000


     [ https://issues.apache.org/jira/browse/KAFKA-6119?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ismael Juma updated KAFKA-6119:
-------------------------------
    Labels: reliability  (was: )

> Silent Data Loss in Kafka011 Transactional Producer
> ---------------------------------------------------
>
>                 Key: KAFKA-6119
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6119
>             Project: Kafka
>          Issue Type: Bug
>          Components: core, producer 
>    Affects Versions: 0.11.0.0, 0.11.0.1
>         Environment: openjdk version "1.8.0_144"
> OpenJDK Runtime Environment (Zulu 8.23.0.3-macosx) (build 1.8.0_144-b01)
> OpenJDK 64-Bit Server VM (Zulu 8.23.0.3-macosx) (build 25.144-b01, mixed mode)
>            Reporter: Gary Y.
>            Priority: Blocker
>              Labels: reliability
>
> Kafka can lose data published by a transactional {{KafkaProducer}} under some circumstances, i.e., data that should be committed atomically may not be fully visible from a consumer with {{read_committed}} isolation level.
>  
> *Steps to reproduce:*
> # Set {{transaction.timeout.ms}} to a low value such as {{100}}
> # Publish two messages in one transaction to different partitions of a topic with a sufficiently long time in-between the messages (e.g., 70 s).
> # Only the second message is visible with {{read_committed}} isolation level.
> See 
> https://github.com/GJL/kafka011-transactional-producer-bug-demo/blob/master/src/main/java/com/garyyao/App.java for a full example. Detailed instructions can be found in the {{README.md}}: https://github.com/GJL/kafka011-transactional-producer-bug-demo
> *Why is this possible?*
> Because the transaction timeout is set to a low value, the transaction will be rolled back quickly after the first message is sent. Indeed, in the broker the following logs could be found:
> {code}
> [2017-10-25 22:54:58,224] INFO [Transaction Coordinator 0]: Initialized transactionalId test-producer-1508964897483 with producerId 5 and producer epoch 0 on partition __transaction_state-10 (kafka.coordinator.transaction.TransactionCoordinator)
> [2017-10-25 22:55:24,260] INFO [Transaction Coordinator 0]: Completed rollback ongoing transaction of transactionalId: test-producer-1508964897483 due to timeout (kafka.coordinator.transaction.TransactionCoordinator)
> {code}
> After rollback, the second message is sent to a different partition than the first message. 
> Upon, transaction commit, {{org.apache.kafka.clients.producer.internals.TransactionManager}} may enqueue the request {{addPartitionsToTransactionHandler}}:
> {code}
> private TransactionalRequestResult beginCompletingTransaction(TransactionResult transactionResult) {
>         if (!newPartitionsInTransaction.isEmpty())
>             enqueueRequest(addPartitionsToTransactionHandler());
>         EndTxnRequest.Builder builder = new EndTxnRequest.Builder(transactionalId, producerIdAndEpoch.producerId,
>                 producerIdAndEpoch.epoch, transactionResult);
>         EndTxnHandler handler = new EndTxnHandler(builder);
>         enqueueRequest(handler);
>         return handler.result;
>     }
> {code}
> As can be seen, the condition is fulfilled if {{newPartitionsInTransaction}} is non-empty. I suspect because the second message goes to a different partition, this condition is satisfied.
> In {{KafkaApis.scala}}, I can see that {{handleAddPartitionToTxnRequest}} eventually may call {{prepareAddPartitions}}:
> {code}
>  def prepareAddPartitions(addedTopicPartitions: immutable.Set[TopicPartition], updateTimestamp: Long): TxnTransitMetadata = {
>     val newTxnStartTimestamp = state match {
>       case Empty | CompleteAbort | CompleteCommit => updateTimestamp
>       case _ => txnStartTimestamp
>     }
>     prepareTransitionTo(Ongoing, producerId, producerEpoch, txnTimeoutMs, (topicPartitions ++ addedTopicPartitions).toSet,
>       newTxnStartTimestamp, updateTimestamp)
>   }
> {code}
> Note that the method's first argument {{newState}} of is always *Ongoing* here. I suspect that this puts the transaction, which should be aborted, to _Ongoing_ again.


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