[jira] [Resolved] (KAFKA-6799) Consumer livelock during consumer group rebalance

["Attila Sasvari (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-6799?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Attila Sasvari resolved KAFKA-6799.
-----------------------------------
    Resolution: Information Provided

> Consumer livelock during consumer group rebalance
> -------------------------------------------------
>
>                 Key: KAFKA-6799
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6799
>             Project: Kafka
>          Issue Type: Bug
>          Components: clients, consumer
>    Affects Versions: 1.0.0, 0.11.0.2, 1.1.0
>            Reporter: Pierre-Henri Dezanneau
>            Assignee: Attila Sasvari
>            Priority: Critical
>
> We have the following environment:
> * 1 kafka cluster with 3 brokers
> * 1 topic with 3 partitions
> * 1 producer
> * 1 consumer group with 3 consumers
> From this setup, we remove one broker from the cluster, the hard way, by simply killing it. Quite often, we see that the consumer group is not rebalanced correctly. By that I mean that all 3 consumers stop consuming and get stuck in a loop, forever.
> The thread dump shows that the consumer threads aren't blocked but run forever in {{AbstractCoordinator.ensureCoordinatorReady}}, holding a lock due to the {{synchonized}} keyword on the calling method. Heartbeat threads are blocked, waiting for the consumer threads to release the lock. This situation prevents all consumers from consuming any more record.
> We build a simple project which seems to reliably demonstrate this:
> {code:sh}
> $ mkdir -p /tmp/sandbox && cd /tmp/sandbox
> $ git clone https://github.com/phdezann/helloworld-kafka-livelock
> $ cd helloworld-kafka-livelock && ./spin.sh
> ...
> livelock detected
> {code}
> {code:sh|title=Consumer thread|borderStyle=solid}
> "kafka-consumer-1@10733" daemon prio=5 tid=0x31 nid=NA runnable
>   java.lang.Thread.State: RUNNABLE
> 	 blocks kafka-coordinator-heartbeat-thread | helloWorldGroup@10728
> 	  at sun.nio.ch.EPollArrayWrapper.epollWait(EPollArrayWrapper.java:-1)
> 	  at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:269)
> 	  at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:93)
> 	  at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:86)
> 	  - locked <0x2a15> (a sun.nio.ch.EPollSelectorImpl)
> 	  - locked <0x2a16> (a java.util.Collections$UnmodifiableSet)
> 	  - locked <0x2a17> (a sun.nio.ch.Util$3)
> 	  at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:97)
> 	  at org.apache.kafka.common.network.Selector.select(Selector.java:684)
> 	  at org.apache.kafka.common.network.Selector.poll(Selector.java:408)
> 	  at org.apache.kafka.clients.NetworkClient.poll(NetworkClient.java:460)
> 	  at org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:261)
> 	  at org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:233)
> 	  at org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:224)
> 	  at org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.awaitMetadataUpdate(ConsumerNetworkClient.java:156)
> 	  at org.apache.kafka.clients.consumer.internals.AbstractCoordinator.ensureCoordinatorReady(AbstractCoordinator.java:228)
> 	  - locked <0x2a0c> (a org.apache.kafka.clients.consumer.internals.ConsumerCoordinator)
> 	  at org.apache.kafka.clients.consumer.internals.AbstractCoordinator.ensureCoordinatorReady(AbstractCoordinator.java:205)
> 	  at org.apache.kafka.clients.consumer.internals.ConsumerCoordinator.poll(ConsumerCoordinator.java:279)
> 	  at org.apache.kafka.clients.consumer.KafkaConsumer.pollOnce(KafkaConsumer.java:1149)
> 	  at org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1115)
> 	  at org.helloworld.kafka.bus.HelloWorldKafkaListener.lambda$createConsumerInDedicatedThread$0(HelloWorldKafkaListener.java:45)
> 	  at org.helloworld.kafka.bus.HelloWorldKafkaListener$$Lambda$42.1776656466.run(Unknown Source:-1)
> 	  at java.lang.Thread.run(Thread.java:748)
> {code}
> {code:sh|title=Heartbeat thread|borderStyle=solid}
> "kafka-coordinator-heartbeat-thread | helloWorldGroup@10728" daemon prio=5 tid=0x36 nid=NA waiting for monitor entry
>   java.lang.Thread.State: BLOCKED
> 	 waiting for kafka-consumer-1@10733 to release lock on <0x2a0c> (a org.apache.kafka.clients.consumer.internals.ConsumerCoordinator)
> 	  at java.lang.Object.wait(Object.java:-1)
> 	  at org.apache.kafka.clients.consumer.internals.AbstractCoordinator$HeartbeatThread.run(AbstractCoordinator.java:955)
> {code}



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