Any failure/restart of a consumer or a broker can also trigger a rebalance.
Thanks, Jun On Mon, Aug 19, 2013 at 6:00 PM, Ian Friedman <i...@flurry.com> wrote: > Jun, I read that FAQ entry you linked, but I am not seeing any Zookeeper > connection loss in the logs. It's rebalancing multiple times per minute, > though. Any idea what else could cause this? We're running kafka 0.7.2 on > approx 400 consumers against a topic with 400 partitions * 3 brokers. > > -- > Ian Friedman > > > On Thursday, August 15, 2013 at 11:52 AM, Jun Rao wrote: > > > Yes, during rebalances, messages could be re-delievered since the new > owner > > of a partition starts fetching from the last checkpointed offset in ZK. > > > > For reasons on why rebalances happen a lot, see > > > https://cwiki.apache.org/confluence/display/KAFKA/FAQ#FAQ-Whyaretheremanyrebalancesinmyconsumerlog%3F > > > > Thanks, > > > > Jun > > > > > > On Thu, Aug 15, 2013 at 8:36 AM, Ian Friedman <i...@flurry.com (mailto: > i...@flurry.com)> wrote: > > > > > It's a simple enough patch, but wouldn't this mean that messages still > in > > > process when a rebalance happens could get delivered to another > consumer if > > > we end up losing the partition? Rebalances seem to happen very > frequently > > > with a lot of consumers for some reason… And it doesn't seem like a > > > consumer is guaranteed or likely to retain ownership of a partition > it's in > > > the middle of consuming after a rebalance. > > > > > > -- > > > Ian Friedman > > > > > > > > > On Thursday, August 15, 2013 at 10:53 AM, Jun Rao wrote: > > > > > > > We are only patching blocker issues in 0.7. 0.8 beta1 has been > released > > > and > > > > most dev effort will be on 0.8 and beyond. That said. This particular > > > > > > case > > > > is easy to fix. If you can port the patch in > > > > https://issues.apache.org/jira/browse/KAFKA-919 o the 0.7 branch , > we > > > > > > > > > > can > > > > commit that to the 0.7 branch. > > > > > > > > Thanks, > > > > > > > > Jun > > > > > > > > > > > > On Wed, Aug 14, 2013 at 9:30 PM, Ian Friedman <i...@flurry.com(mailto: > i...@flurry.com) (mailto: > > > i...@flurry.com (mailto:i...@flurry.com))> wrote: > > > > > > > > > Ugh. > > > > > > > > > > Is there any way to make this work in 0.7, or is transitioning to > 0.8 > > > the > > > > > only way? My operations engineers spent a lot of effort in > configuring > > > > > > > > > > and > > > > > hardening our 0.7 production install, and 0.8 isn't released yet. > Not > > > > > > > > > > to > > > > > mention having to integrate the new client side code. > > > > > > > > > > Either way, thanks for all your help Jun. > > > > > > > > > > -- > > > > > Ian Friedman > > > > > > > > > > > > > > > On Thursday, August 15, 2013 at 12:21 AM, Jun Rao wrote: > > > > > > > > > > > Yes, this is an issue and has been fixed in 0.8. > > > > > > > > > > > > Thanks, > > > > > > > > > > > > Jun > > > > > > > > > > > > > > > > > > On Wed, Aug 14, 2013 at 5:21 PM, Ian Friedman > > > > > > <i...@flurry.com(mailto: > i...@flurry.com)(mailto: > > > i...@flurry.com (mailto:i...@flurry.com)) (mailto: > > > > > i...@flurry.com (mailto:i...@flurry.com))> wrote: > > > > > > > > > > > > > Hey guys, > > > > > > > > > > > > > > I designed my consumer app (running on 0.7) to run with > autocommit > > > off > > > > > and > > > > > > > commit manually once it was done processing a record. The > intent > > > > > > > > > > > > > > > > > > > > > > > > > > was so > > > > > > > that if a consumer died while processing a message, the offset > > > > > > > > > > > > > > > > > > > > > would > > > > > > > > > > > > > > > > > > > > > > > > > > > > not be > > > > > > > committed, and another box would pick up the partition and > > > > > > > > > > > > > > > > > > > > > > > > > > reprocess > > > > > > > > > > > > > > > > > > > > > the > > > > > > > message. This seemed to work fine with small numbers of > consumers > > > > > > > > > > > > > > > > > > > > > (~10). > > > > > > > But now that I'm scaling it out, I'm running into a problem > where > > > > > > > > > > > > > > > > > > > > > > > > > > it > > > > > > > > > > > > > > > > > > > > > looks > > > > > > > like messages that consumers picked up and then errored on are > not > > > > > > > > > > > > > > > > > > > > > getting > > > > > > > processed on another machine. > > > > > > > > > > > > > > After investigating the logs and the partition offsets in > > > zookeeper, I > > > > > > > found that in ZookeeperConsumerConnector.scala > > > > > > > > > > > > > > > > > > > > > closeFetchersForQueues, > > > > > > > called during the rebalance process, will commit the offset > > > > > > > > > > > > > > > > > > > > > regardless > > > > > > > > > > > > > > > > > > > > > > > > > > > > of > > > > > > > the autocommit status. So it looks like even if my consumer is > in > > > > > > > > > > > > > > > > > > > > > > > > > > the > > > > > > > middle of processing a message, the offset will be committed, > and > > > > > > > > > > > > > > > > > > > > > even > > > > > > > > > > > > > > > > > > > > > > > > > > > > if > > > > > > > the processing fails, it will never be picked up again. Now > that I > > > > > > > > > > > > > > > > > > > > > have a > > > > > > > lot of consumer nodes, the rebalancer is going off a lot more > often > > > > > > > > > > > > > > > > > > > > > and I'm > > > > > > > running into this constantly. > > > > > > > > > > > > > > Were my assumptions faulty? Did I design this wrong? After > reading > > > the > > > > > > > comment in the code I understand that if it didn't commit the > > > > > > > > > > > > > > > > > > > > > offset > > > > > > > > > > > > > > > > > > > > > > > > > > > > there, > > > > > > > the message would just get immediately consumed by whoever > ended up > > > > > > > > > > > > > > > > > > > > > owning > > > > > > > the partition, even if we were in the middle of consuming it > > > > > > > > > > > > > > > > > > > > > elsewhere, and > > > > > > > we'd get unintentional duplicate delivery. How can I make it > work > > > > > > > > > > > > > > > > > > > > > > > > > > the > > > > > > > > > > > > > > > > > > > > > way > > > > > > > I've described? Is there any way? > > > > > > > > > > > > > > Thanks in advance, > > > > > > > > > > > > > > -- > > > > > > > Ian Friedman > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
