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

["Pierre-Henri Dezanneau (JIRA)" <ji...@apache.org>]

Pierre-Henri Dezanneau created KAFKA-6799:
---------------------------------------------

             Summary: 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: 1.1.0, 0.11.0.2, 1.0.0
            Reporter: Pierre-Henri Dezanneau


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 detecte
{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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