Hello Gwen, Thanks for fast response!
Btw, congrats on officially becoming a Kafka committer and thanks, among other things, for great "Intro to Kafka" video http://shop.oreilly.com/product/0636920038603.do ! Have to read more docs and/or source. I thought this scenario is possible because replica can fall behind (replica.lag.max.messages) and still be considered ISR. Then I assumed also write can be ACKed by any ISR, and then why not by one which has fallen more behind. Kind regards, Stevo Slavic. On Tue, Jul 7, 2015 at 4:47 PM, Gwen Shapira <gshap...@cloudera.com> wrote: > I am not sure "different replica" can ACK the second back of messages > while not having the first - from what I can see, it will need to be > up-to-date on the latest messages (i.e. correct HWM) in order to ACK. > > On Tue, Jul 7, 2015 at 7:13 AM, Stevo Slavić <ssla...@gmail.com> wrote: > > Hello Apache Kafka community, > > > > Documentation for min.insync.replicas in > > http://kafka.apache.org/documentation.html#brokerconfigs states: > > > > "When used together, min.insync.replicas and request.required.acks allow > > you to enforce greater durability guarantees. A typical scenario would be > > to create a topic with a replication factor of 3, set min.insync.replicas > > to 2, and produce with request.required.acks of -1. This will ensure that > > the producer raises an exception if a majority of replicas do not > receive a > > write." > > > > Correct me if wrong (doc reference?), I assume min.insync.replicas > includes > > lead, so with min.insync.replicas=2, lead and one more replica besides > lead > > will have to ACK writes. > > > > In such setup, with minimalistic 3 brokers cluster, given that > > - all 3 replicas are insync > > - a batch of messages is written and ends up on lead and one replica ACKs > > - another batch of messages ends up on lead and different replica ACKs > > > > Is it possible that when lead crashes, while replicas didn't catch up, > > (part of) one batch of messages could be lost (since one replica becomes > a > > new lead, and it's only serving all reads and requests, and replication > is > > one way)? > > > > Kind regards, > > Stevo Slavic. >