If we just wanted to remove deprecation and let both co-exist, that would be also viable, though `poll(0)` is still a hack and it would be ideal to provide official approach to do so.
On Wed, Aug 7, 2019 at 4:24 PM Jungtaek Lim <kabh...@gmail.com> wrote: > Hi devs, > > I'm trying to replace deprecated poll(long) with poll(Duration), and > realized there's no alternative which behaves exactly same as poll(0), as > poll(0) has been used as a hack to only update metadata instead of pulling > records. poll(Duration.ZERO) wouldn't behave same since even updating > metadata will be timed-out. So now end users would need to give more > timeout and even pull some records even they're only interested in metadata. > > I looked back some KIPs which brought the change, and "discarded" KIP > (KIP-288 [1]) actually proposed a new API which only pulls metadata. > KIP-266 [2] is picked up instead but it didn't cover all the things what > KIP-288 proposed. I'm seeing some doc explaining poll(0) hasn't been > supported officially, but the hack has been widely used and they can't be > ignored. > > Kafka test code itself relies on either deprecated poll(0), > or updateAssignmentMetadataIfNeeded, which seems to be private API only for > testing. > (Btw, I'd try out replacing poll(0) to updateAssignmentMetadataIfNeeded as > avoiding deprecated method - if it works I'll submit a PR.) > > I'm feeling that it would be ideal to expose > `updateAssignmentMetadataIfNeeded` to the public API, maybe with renaming > as `waitForAssignment` which was proposed in KIP-288 if it feels too long. > > What do you think? If it sounds feasible I'd like to try out contribution > on this. I'm new to contribute Kafka community, so not sure it would > require a new KIP or not. > > Thanks, > Jungtaek Lim (HeartSaVioR) > > 1. > https://cwiki.apache.org/confluence/display/KAFKA/KIP-288%3A+%5BDISCARDED%5D+Consumer.poll%28%29+timeout+semantic+change+and+new+waitForAssignment+method > 2. > https://cwiki.apache.org/confluence/display/KAFKA/KIP-266%3A+Fix+consumer+indefinite+blocking+behavior > > -- Name : Jungtaek Lim Blog : http://medium.com/@heartsavior Twitter : http://twitter.com/heartsavior LinkedIn : http://www.linkedin.com/in/heartsavior
