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https://issues.apache.org/jira/browse/KAFKA-2082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14391607#comment-14391607
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Evan Huus commented on KAFKA-2082:
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We are using ZK connection drops as a convenient way to take brokers out of the
cluster without a graceful shutdown. Having them fail over to another zookeeper
would defeat the purpose there.
> Kafka Replication ends up in a bad state
> ----------------------------------------
>
> Key: KAFKA-2082
> URL: https://issues.apache.org/jira/browse/KAFKA-2082
> Project: Kafka
> Issue Type: Bug
> Components: replication
> Affects Versions: 0.8.2.1
> Reporter: Evan Huus
> Assignee: Neha Narkhede
> Priority: Critical
>
> While running integration tests for Sarama (the go client) we came across a
> pattern of connection losses that reliably puts kafka into a bad state:
> several of the brokers start spinning, chewing ~30% CPU and spamming the logs
> with hundreds of thousands of lines like:
> {noformat}
> [2015-04-01 13:08:40,070] WARN [Replica Manager on Broker 9093]: Fetch
> request with correlation id 111094 from client ReplicaFetcherThread-0-9093 on
> partition [many_partition,1] failed due to Leader not local for partition
> [many_partition,1] on broker 9093 (kafka.server.ReplicaManager)
> [2015-04-01 13:08:40,070] WARN [Replica Manager on Broker 9093]: Fetch
> request with correlation id 111094 from client ReplicaFetcherThread-0-9093 on
> partition [many_partition,6] failed due to Leader not local for partition
> [many_partition,6] on broker 9093 (kafka.server.ReplicaManager)
> [2015-04-01 13:08:40,070] WARN [Replica Manager on Broker 9093]: Fetch
> request with correlation id 111095 from client ReplicaFetcherThread-0-9093 on
> partition [many_partition,21] failed due to Leader not local for partition
> [many_partition,21] on broker 9093 (kafka.server.ReplicaManager)
> [2015-04-01 13:08:40,071] WARN [Replica Manager on Broker 9093]: Fetch
> request with correlation id 111095 from client ReplicaFetcherThread-0-9093 on
> partition [many_partition,26] failed due to Leader not local for partition
> [many_partition,26] on broker 9093 (kafka.server.ReplicaManager)
> [2015-04-01 13:08:40,071] WARN [Replica Manager on Broker 9093]: Fetch
> request with correlation id 111095 from client ReplicaFetcherThread-0-9093 on
> partition [many_partition,1] failed due to Leader not local for partition
> [many_partition,1] on broker 9093 (kafka.server.ReplicaManager)
> [2015-04-01 13:08:40,071] WARN [Replica Manager on Broker 9093]: Fetch
> request with correlation id 111095 from client ReplicaFetcherThread-0-9093 on
> partition [many_partition,6] failed due to Leader not local for partition
> [many_partition,6] on broker 9093 (kafka.server.ReplicaManager)
> [2015-04-01 13:08:40,072] WARN [Replica Manager on Broker 9093]: Fetch
> request with correlation id 111096 from client ReplicaFetcherThread-0-9093 on
> partition [many_partition,21] failed due to Leader not local for partition
> [many_partition,21] on broker 9093 (kafka.server.ReplicaManager)
> [2015-04-01 13:08:40,072] WARN [Replica Manager on Broker 9093]: Fetch
> request with correlation id 111096 from client ReplicaFetcherThread-0-9093 on
> partition [many_partition,26] failed due to Leader not local for partition
> [many_partition,26] on broker 9093 (kafka.server.ReplicaManager)
> {noformat}
> This can be easily and reliably reproduced using the {{toxiproxy-final}}
> branch of https://github.com/Shopify/sarama which includes a vagrant script
> for provisioning the appropriate cluster:
> - {{git clone https://github.com/Shopify/sarama.git}}
> - {{git checkout toxiproxy-final}}
> - {{vagrant up}}
> - {{TEST_SEED=1427917826425719059 DEBUG=true go test -v}}
> After the test finishes (it fails because the cluster ends up in a bad
> state), you can log into the cluster machine with {{vagrant ssh}} and inspect
> the bad nodes. The vagrant script provisions five zookeepers and five brokers
> in {{/opt/kafka-9091/}} through {{/opt/kafka-9095/}}.
> Additional context: the test produces continually to the cluster while
> randomly cutting and restoring zookeeper connections (all connections to
> zookeeper are run through a simple proxy on the same vm to make this easy).
> The majority of the time this works very well and does a good job exercising
> our producer's retry and failover code. However, under certain patterns of
> connection loss (the {{TEST_SEED}} in the instructions is important), kafka
> gets confused. The test never cuts more than two connections at a time, so
> zookeeper should always have quorum, and the topic (with three replicas)
> should always be writable.
> Completely restarting the cluster via {{vagrant reload}} seems to put it back
> into a sane state.
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