Btw, after we complete KAFKA-1000 (offset management in Kafka) it should be reasonable to commit offsets on every message as long as the optional metadata portion of the offset commit request is small/empty.
Thanks, Joel On Wed, Oct 16, 2013 at 10:35 AM, Jason Rosenberg <j...@squareup.com> wrote: > That would be great. Additionally, in the new api, it would be awesome > augment the default auto-commit functionality to allow client code to mark > a message for commit only after processing a message successfully! > > > On Wed, Oct 16, 2013 at 7:52 AM, Jun Rao <jun...@gmail.com> wrote: > >> For manual offset commits, it will be useful to have some kind of API that >> informs the client when a rebalance is going to happen. We can think about >> this when we do the client rewrite. >> >> Thanks, >> >> Jun >> >> >> On Tue, Oct 15, 2013 at 9:21 PM, Jason Rosenberg <j...@squareup.com> wrote: >> >> > Jun, >> > >> > Yes, sorry, I think that was the basis for my question. When auto >> commit >> > is enabled, special care is taken to make sure things are auto-committed >> > during a rebalance. This is needed because when a topic moves off of a >> > consumer thread (since it is being rebalanced to another one), it's as if >> > that topic is being shutdown on that connector, and any not-yet-committed >> > messages need to be committed before letting go of the topic. >> > >> > So, my question is around trying to understand if there's a way I can >> > reproduce similar functionality using my own sync auto commit >> > implementation (and I'm not sure there is). It seems that when there's a >> > rebalance, all processed but not-yet-committed offsets will not be >> > committed, and thus there will be no way to prevent pretty massive >> > duplicate consumption on a rebalance. Is that about right? Or is there >> > someway around this that I'm not seeing? >> > >> > The auto-commit functionality that's builtin is so close to being all >> that >> > anyone would need, except it has a glaring weakness, in that it will >> cause >> > messages to be lost from time to time, and so I don't know that it will >> > meet the needs of trying to have reliable delivery (with duplicates ok). >> > >> > Jason >> > >> > >> > On Tue, Oct 15, 2013 at 9:00 PM, Jun Rao <jun...@gmail.com> wrote: >> > >> > > If auto commit is disabled, the consumer connector won't call >> > commitOffsets >> > > during rebalancing. >> > > >> > > Thanks, >> > > >> > > Jun >> > > >> > > >> > > On Tue, Oct 15, 2013 at 4:16 PM, Jason Rosenberg <j...@squareup.com> >> > wrote: >> > > >> > > > I'm looking at implementing a synchronous auto offset commit >> solution. >> > > > People have discussed the need for this in previous >> > > > threads......Basically, in my consumer loop, I want to make sure a >> > > message >> > > > has been actually processed before allowing it's offset to be >> > committed. >> > > > But I don't want to commit on every message, since that would be too >> > > > expensive. So, I want to use the 'auto.commit.interval.ms' to >> > > > periodically >> > > > call commitOffsets, but only after a message is processed, but not >> > after >> > > > the next message has been issued via a call to 'next()' on the >> > > > ConsumerIterator. >> > > > >> > > > The builtin 'auto.commit.enable' feature unfortunately allows commits >> > to >> > > > happen on any message that has been returned via >> > ConsumerIterator.next(). >> > > > But if the consumer goes down before actually processing the >> message, >> > or >> > > > if it hangs indefinitely for some reason, then this message will get >> > > > committed before it has actually been consumed successfully. >> > > > >> > > > I think there are issues with trying to implement this on top of the >> > > > high-level consumer api. First, I need to worry about multiple >> threads >> > > > consuming in the same connector (so for now I'm limiting this to >> > support >> > > > only 1 thread). >> > > > >> > > > Also, when shutting down the connector, I need to make sure any >> pending >> > > > messages are committed before allowing the connector to shutdown. >> So, >> > > that >> > > > seems easy enough to handle. >> > > > >> > > > One thing I'm more concerned with, is what happens when there's a >> > > consumer >> > > > rebalance. Looking at the ZookeeperConsumerConnector code, it seems >> > > there >> > > > are explicit calls to commitOffsets during the rebalance. I'm not >> sure >> > > how >> > > > to handle that from the high-level api (and do I need to worry about >> > > > that?). >> > > > >> > > > Thanks for any insight. >> > > > >> > > > Jason >> > > > >> > > >> > >>
