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From "Guozhang Wang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (KAFKA-6098) Delete and Re-create topic operation could result in race condition
Date Fri, 20 Oct 2017 15:42:00 GMT
Guozhang Wang created KAFKA-6098:
------------------------------------

             Summary: Delete and Re-create topic operation could result in race condition
                 Key: KAFKA-6098
                 URL: https://issues.apache.org/jira/browse/KAFKA-6098
             Project: Kafka
          Issue Type: Bug
            Reporter: Guozhang Wang
             Fix For: 1.0.0


Here is the following process to re-produce this issue:

1. Delete a topic using the delete topic request.
2. Confirm the topic is deleted using the list topics request.
3. Create the topic using the create topic request.

In step 3) a race condition can happen that the response returns a {{TOPIC_ALREADY_EXISTS}}
error code, indicating the topic has already existed.

The root cause of the above issue is in the {{TopicDeletionManager}} class:

{code}
controller.partitionStateMachine.handleStateChanges(partitionsForDeletedTopic.toSeq, OfflinePartition)
controller.partitionStateMachine.handleStateChanges(partitionsForDeletedTopic.toSeq, NonExistentPartition)
topicsToBeDeleted -= topic
partitionsToBeDeleted.retain(_.topic != topic)
kafkaControllerZkUtils.deleteTopicZNode(topic)
kafkaControllerZkUtils.deleteTopicConfigs(Seq(topic))
kafkaControllerZkUtils.deleteTopicDeletions(Seq(topic))
controllerContext.removeTopic(topic)
{code}

I.e. it first update the broker's metadata cache through the ISR and metadata update request,
then delete the topic zk path, and then delete the topic-deletion zk path. However, upon handling
the create topic request, the broker will simply try to write to the topic zk path directly.
Hence there is a race condition that between brokers update their metadata cache (hence list
topic request not returning this topic anymore) and zk path for the topic be deleted (hence
the create topic succeed).

The reason this problem could be exposed, is through current handling logic of the create
topic response, most of which takes {{TOPIC_ALREADY_EXISTS}} as "OK" and moves on, and the
zk path will be deleted later, hence leaving the topic to be not created at all:

https://github.com/apache/kafka/blob/249e398bf84cdd475af6529e163e78486b43c570/streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsKafkaClient.java#L221

https://github.com/apache/kafka/blob/1a653c813c842c0b67f26fb119d7727e272cf834/connect/runtime/src/main/java/org/apache/kafka/connect/util/TopicAdmin.java#L232

And the user may not retry.



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