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From Jun Rao <jun...@gmail.com>
Subject Re: ConsumerRebalanceFailedException
Date Mon, 02 Dec 2013 16:55:12 GMT
Is the failure on the last rebalance? If so, some partitions will not have
any consumers. A common reason for rebalance failure is that there is
conflict in owning partitions among different consumers in the same group.
Increasing the # retries and the amount of backoff time btw retires should
help. Our default setting should be good enough if there are not too many
topics being subscribed and the ZK latency is normal.

Thanks,

Jun


On Mon, Dec 2, 2013 at 6:57 AM, Yu, Libo <libo.yu@citi.com> wrote:

> Actually, I saw this line in the log : can't rebalance after 4 retries.
> What should I expect in this case? All consumers threads failed or only
> some of them?
> If I increase the number of retries or delay between retries, will that
> help?
>
> Regards,
>
> Libo
>
>
> -----Original Message-----
> From: Jun Rao [mailto:junrao@gmail.com]
> Sent: Friday, November 29, 2013 8:50 PM
> To: users@kafka.apache.org
> Subject: Re: ConsumerRebalanceFailedException
>
> Transient rebalance failures are ok. However, it's important that the last
> rebalance in a sequence succeeds. Otherwise, some of the partitions will
> not be consumed by any consumers.
>
> Thanks,
>
> Jun
>
>
> On Fri, Nov 29, 2013 at 10:44 AM, Yu, Libo <libo.yu@citi.com> wrote:
>
> > You are right, Joe. I checked our brokers' log. We have three brokers.
> > All of them failed to connect to zk at some point.
> > So they were offline and later reregistered themselves with the zk. I
> > don't know how many rebalance should be triggered in that case. There
> > is only one exception found in consumer's log. My question is whether
> > users need to do anything to handle ConsumerRebalanceFailedException.
> >
> > This is from consumer log:
> >
> > [28/11/13 16:38:56:056 PM EST] 102 ERROR
> > consumer.ZookeeperConsumerConnector: [xxxxxxxxxx ], error during
> > syncedRebalance
> > kafka.common.ConsumerRebalanceFailedException: xxxxxxxxx can't
> > rebalance after 4 retries
> >         at
> > kafka.consumer.ZookeeperConsumerConnector$ZKRebalancerListener.syncedR
> > eb
> > alance(ZookeeperConsumerConnector.scala:397)
> >         at
> > kafka.consumer.ZookeeperConsumerConnector$ZKRebalancerListener$$anon$1
> > .r
> > un(ZookeeperConsumerConnector.scala:326)
> >
> > Regards,
> >
> > Libo
> >
> >
> > -----Original Message-----
> > From: Joe Stein [mailto:joe.stein@stealth.ly]
> > Sent: Friday, November 29, 2013 11:57 AM
> > To: users@kafka.apache.org
> > Subject: Re: ConsumerRebalanceFailedException
> >
> > What is the full stack trace?  if you see "can't rebalance after 4
> retries"
> > then likely the problem is the broker is down or not available
> >
> > /*******************************************
> >  Joe Stein
> >  Founder, Principal Consultant
> >  Big Data Open Source Security LLC
> >  http://www.stealth.ly
> >  Twitter: @allthingshadoop <http://www.twitter.com/allthingshadoop>
> > ********************************************/
> >
> >
> > On Fri, Nov 29, 2013 at 11:31 AM, Yu, Libo <libo.yu@citi.com> wrote:
> >
> > > We found our consumer stopped working after this exception occurred.
> > > Can the consumer recover from such an exception?
> > >
> > > Regards,
> > >
> > > Libo
> > >
> > >
> > > -----Original Message-----
> > > From: Florin Trofin [mailto:ftrofin@adobe.com]
> > > Sent: Tuesday, July 16, 2013 4:20 PM
> > > To: users@kafka.apache.org
> > > Subject: Re: ConsumerRebalanceFailedException
> > >
> > > Yes, I think these are two separate issues.
> > >
> > > F.
> > >
> > > On 7/16/13 11:32 AM, "Joel Koshy" <jjkoshy.w@gmail.com> wrote:
> > >
> > > >From a user's perspective, ConsumerRebalanceException is a bit
> > > >cryptic -I think the other thread was to provide a more informative
> > > >message and also be able to recover when a broker does come up
> > > >(fixed in KAFKA-969).
> > > >
> > > >Thanks,
> > > >
> > > >Joel
> > > >
> > > >On Tue, Jul 16, 2013 at 11:04 AM, Vaibhav Puranik
> > > ><vpuranik@gmail.com>
> > > >wrote:
> > > >> Thank you Joel.
> > > >>
> > > >> In a different but related thread, somebody is asking to rename
> > > >> the exception as NoBrokerAvailableExcption. But given the
> > > >> description above, the exception seems to be named appropriately.
> > > >>
> > > >> Regards,
> > > >> Vaibhav
> > > >>
> > > >>
> > > >> On Tue, Jul 16, 2013 at 12:05 AM, Joel Koshy
> > > >><jjkoshy.w@gmail.com>
> > > >>wrote:
> > > >>
> > > >>> Yes - rebalance => consumers trying to coordinate through ZK.
> > > >>> Rebalances can happen when one or more of the following happen:
> > > >>> - a consumed topic partition appears or disappears - i.e., if
a
> > > >>> broker comes or goes.
> > > >>> - a consumer instance in the group comes or goes "goes" could
> > > >>> also be triggered by session expirations in zookeeper -
> > > >>> typically caused by client-side GC or flaky connections to
> zookeeper.
> > > >>>
> > > >>> On Mon, Jul 15, 2013 at 10:15 AM, Vaibhav Puranik
> > > >>> <vpuranik@gmail.com>
> > > >>> wrote:
> > > >>> > Hi all,
> > > >>> >
> > > >>> > We have a small Kafka cluster (0.7.1 - 3 nodes) in EC2. The
> > > >>> > load is
> > > >>>about
> > > >>> > 200 million events per day, each being few kilobytes. We
have
> > > >>> > a
> > > >>>single
> > > >>> node
> > > >>> > zookeeper.
> > > >>> >
> > > >>> > Yesterday suddenly our Kafka clients started throwing the
> > > >>> > following
> > > >>> > exception:
> > > >>> > java.lang.RuntimeException:
> > > >>> kafka.common.ConsumerRebalanceFailedException:
> > > >>> >
> > > >>>CONSUMER_GROUP_NAME_ip-00-00-00-00.ec2.internal-1373821190828-5f7
> > > >>>8e
> > > >>>9a
> > > >>>f
> > > >>> > can't rebalance after 4 retries
> > > >>> >     at
> > > >>> >
> > > >>>
> > > >>>com.gumgum.kafka.consumer.KafkaTemplate.executeWithBatch(KafkaTem
> > > >>>pl
> > > >>>at
> > > >>>e.j
> > > >>>ava:59)
> > > >>> >     at
> > > >>> >
> > > >>>
> > > >>>com.gumgum.storm.fileupload.GenericKafkaSpout.nextTuple(GenericKa
> > > >>>fk
> > > >>>aS
> > > >>>pou
> > > >>>t.java:73)
> > > >>> >     at
> > > >>> >
> > > >>>
> > > >>>backtype.storm.daemon.executor$fn__3968$fn__4009$fn__4010.invoke(
> > > >>>ex
> > > >>>ec
> > > >>>uto
> > > >>>r.clj:433)
> > > >>> >     at
> > > >>> > backtype.storm.util$async_loop$fn__465.invoke(util.clj:377)
> > > >>> >
> > > >>> > None of the Kafka clients (ConsumerConenctor class) would
start.
> > > >>> > They
> > > >>> would
> > > >>> > fail with the exception.
> > > >>> >
> > > >>> > We tried restarting the clilents, restarting the zookeeper
as
> well.
> > > >>>But
> > > >>> > finally it all started working when we restarted all of our
> > > >>> > kafka
> > > >>> brokers.
> > > >>> > We didn't lose any data because producers (going directly
to
> > > >>> > the
> > > >>>brokers
> > > >>> > through a load balancer) were working fine.
> > > >>> >
> > > >>> > I tried googling this issue and looks like lot of people
have
> > > >>> > faced
> > > >>>it,
> > > >>> but
> > > >>> > couldn't get anything concrete.
> > > >>> >
> > > >>> > Given this, I have two questions:
> > > >>> >
> > > >>> > It will be nice if you can tell me why this can happen or
> > > >>> > point me
> > > >>>to a
> > > >>> > link where I can understand it better. What does Consumer
> > > >>> > Rebalancing
> > > >>> mean?
> > > >>> > Does that mean consumers are trying to coordinate amongst
> > > >>> > themselves
> > > >>> using
> > > >>> > Zookeeper?
> > > >>> >
> > > >>> > On a separate note, are there any JMX parameters I need to
be
> > > >>>monitoring
> > > >>> to
> > > >>> > make sure that my kafka cluster is healthy? How can I keep
> > > >>> > watch on
> > > >>>my
> > > >>> > kafka cluster?
> > > >>> >
> > > >>> > Regards,
> > > >>> > Vaibhav Puranik
> > > >>> > GumGum
> > > >>>
> > >
> > >
> >
>

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