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From Joel Koshy <jjkosh...@gmail.com>
Subject Re: Broker rejoin with big replica lag
Date Wed, 05 Feb 2014 22:04:15 GMT

> topics are all caught up, but I have one high volume topic (around
> 40K msgs/sec) that is taking much longer.  I just took a few samples
> of Replica-MaxLag to see how long it would take to catch up.
> Currently, it is behind about 12.5 million messages and is catching
> up at a rate of about 1600 msgs/sec.  At that rate, it’ll take
> around 9 days before the replica is caught up to the leader.
> 
> Is there any way to speed this up?

During the period your high-volume topic is under-replicated you can
temporarily try one or both of the following:
- Increasing num.replica.fetchers (defaults is one)
- If you don't have too many topic-partitions you can also increase
  replica.fetch.max.bytes.

> Or, alternatively, I don’t actually care about this topic’s
> history.  It is a new topic, and I know that it doesn't yet have any
> consumers.  I’d be fine with instructing both brokers to drop
> old logs and just start from the top of the log.  I could do this by
> manually deleting the topic (kafka data files and in zookeeper), but
> to do so properly with 0.8.0 I think I’d have to shut down the
> whole cluster, correct?  I’d rather not do this, as another
> topic does have a consumer and I don’t want to lose messages for
> it.

Right - or you could do a rolling bounce and change the retention
settings (http://kafka.apache.org/documentation.html#brokerconfigs) of
that topic to something low so it gets expired and then do another
rolling bounce to remove the override.

-- 
Joel

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