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From "Jun Rao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-693) Consumer rebalance fails if no leader available for a partition and stops all fetchers
Date Sun, 13 Jan 2013 22:34:12 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13552341#comment-13552341
] 

Jun Rao commented on KAFKA-693:
-------------------------------

Ok. This is actually a real problem. During rebalance, we actually try to get the leader even
though we don't really need it at rebalancing time. The fix seems easy.

In ZKRebalancerListener.addPartitionTopicInfo(), we don't really need to get the leaderId,
which is not used in PartitionTopicInfo. So, we can just get rid of that code. We can also
get rid of the code in rebalance() that computes leaderIdForPartitionsMap.
                
> Consumer rebalance fails if no leader available for a partition and stops all fetchers
> --------------------------------------------------------------------------------------
>
>                 Key: KAFKA-693
>                 URL: https://issues.apache.org/jira/browse/KAFKA-693
>             Project: Kafka
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 0.8
>            Reporter: Maxime Brugidou
>         Attachments: mirror_debug.log, mirror.log
>
>
> I am currently experiencing this with the MirrorMaker but I assume it happens for any
rebalance. The symptoms are:
> I have replication factor of 1
> 1. If i start the MirrorMaker (bin/kafka-run-class.sh kafka.tools.MirrorMaker --consumer.config
mirror-consumer.properties  --producer.config mirror-producer.properties --blacklist 'xdummyx'
--num.streams=1 --num.producers=1) with a broker down
> 1.1 I set the refresh.leader.backoff.ms to 600000 (10min) so that the ConsumerFetcherManager
doesn't retry to often to get the unavailable partitions
> 1.2 The rebalance starts at the init step and fails: Exception in thread "main" kafka.common.ConsumerRebalanceFailedException:
KafkaMirror_mirror-01-1357893495345-fac86b15 can't rebalance after 4 retries
> 1.3 After the exception, everything stops (fetchers and queues)
> 1.4 I attached the full logs (info & debug) for this case
> 2. If i start the MirrorMaker with all the brokers up and then kill a broker
> 2.1 The first rebalance is successful
> 2.2 The consumer will handle correctly the broker down and stop the associated ConsumerFetcherThread
> 2.3 The refresh.leader.backoff.ms to 600000 works correctly
> 2.4 If something triggers a rebalance (new topic, partition reassignment...), then we
go back to 1., the rebalance fails and stops everything.
> I think the desired behavior is to consumer whatever is available, and try later at some
intervals. I would be glad to help on that issue although the Consumer code seems a little
tough to get on.

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