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Kafka >> mail # user >> Can't connect to a server if not enough partitions


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Jason Rosenberg 2013-05-09, 05:16
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Neha Narkhede 2013-05-09, 05:57
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Jason Rosenberg 2013-05-09, 06:51
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Re: Can't connect to a server if not enough partitions
Currently, when creating a topic, we require the number of live brokers to
be greater than the replication factor. Once the topic is created, the
number of live brokers can be less than the replication factor.

Thanks,

Jun
On Wed, May 8, 2013 at 11:50 PM, Jason Rosenberg <[EMAIL PROTECTED]> wrote:

> Neha,
>
> Thanks, I think I did understand what was going (despite the error
> message).  And my question stands, if a broker is momentarily down,
> shouldn't we still be able to create a topic?  If we send a message to a
> topic it will succeed, even if not all replicas are available.  Why should
> the initial message be any different?
>
> Jason
>
>
> On Wed, May 8, 2013 at 10:57 PM, Neha Narkhede <[EMAIL PROTECTED]
> >wrote:
>
> > I think this error message is somewhat misleading since we create topic
> on
> > the first metadata request. It is complaining that a topic with the
> > required replication factor cannot be created if there aren't enough
> > brokers to satisfy the replication factor. This is expected behavior
> > whether you use auto creation of topics or manual creation. However, the
> > metadata requests will always give you correct information about existing
> > topics.
> >
> > Thanks,
> > Neha
> >
> >
> > On Wed, May 8, 2013 at 10:15 PM, Jason Rosenberg <[EMAIL PROTECTED]>
> wrote:
> >
> > > With 0.8.0, I'm seeing that an initial metadata request fails, if the
> > > number of running brokers is fewer than the configured replication
> > factor:
> > >
> > > 877 [kafka-request-handler-0] ERROR kafka.server.KafkaApis  -
> > > [KafkaApi-1946108683] Error while retrieving topic metadata
> > > kafka.admin.AdministrationException: replication factor: 2 larger than
> > > available brokers: 1
> > > at kafka.admin.AdminUtils$.assignReplicasToBrokers(AdminUtils.scala:62)
> > > at
> > kafka.admin.CreateTopicCommand$.createTopic(CreateTopicCommand.scala:92)
> > > at
> > >
> > >
> >
> kafka.server.KafkaApis$$anonfun$handleTopicMetadataRequest$1.apply(KafkaApis.scala:409)
> > > at
> > >
> > >
> >
> kafka.server.KafkaApis$$anonfun$handleTopicMetadataRequest$1.apply(KafkaApis.scala:401)
> > > at scala.collection.immutable.Set$Set1.foreach(Set.scala:81)
> > > at
> kafka.server.KafkaApis.handleTopicMetadataRequest(KafkaApis.scala:400)
> > > at kafka.server.KafkaApis.handle(KafkaApis.scala:61)
> > > at kafka.server.KafkaRequestHandler.run(KafkaRequestHandler.scala:41)
> > > at java.lang.Thread.run(Thread.java:680)
> > >
> > > However, if after connecting, the number of brokers goes down,
> producing
> > > clients have no problems continuing sending messages, etc.
> > >
> > > So, I thought the idea was that once a replica becomes available, it
> will
> > > be caught up with messages it might have missed, etc.  This is good
> > because
> > > it makes doing things like rolling restarts of the brokers possible,
> etc.
> > >  But it's a problem if a rolling restart happens at the same time a new
> > > client is coming online to try and initialize a connection.
> > >
> > > Thoughts?
> > >
> > > Shouldn't the requirements be the same for initial connections as
> ongoing
> > > connections?
> > >
> > > Jason
> > >
> >
>