@matthias what are the alternatives to get rid of this issue? When the lag starts increasing, we have alerts configured on our monitoring system in Datadog which starts sending alerts and alarms to reliability teams. I know in kafka the inactive consumer group is cleared up after 7 days however not sure if that is the case with topics that were consumed previously and not consumed now.
Does creation of new consumer group (setting a different application.id) on streams application an option here? On Thu, Aug 17, 2023 at 7:03 AM Matthias J. Sax <mj...@apache.org> wrote: > Well, it's kinda expected behavior. It's a split brain problem. > > In the end, you use the same `application.id / group.id` and thus the > committed offsets for the removed topics are still in > `__consumer_offsets` topics and associated with the consumer group. > > If a tool inspects lags and compares the latest committed offsets to > end-offsets it looks for everything it finds in the `__consumer_offsets` > topics for the group in question -- the tool cannot know that you > changed the application and that is does not read from those topics any > longer (and thus does not commit any longer). > > I am not sure from top of my head if you could do a manual cleanup for > the `application.id` and topics in question and delete the committed > offsets from the `__consumer_offsets` topic -- try to checkout `Admin` > client and/or the command line tools... > > In know that it's possible to delete committed offsets for a consumer > group (if a group becomes inactive, the broker would also cleanup all > group metadata after a configurable timeout), but I am not sure if > that's for the entire consumer group (ie, all topic) or if you can do it > on a per-topic basis, too. > > > HTH, > -Matthias > > > On 8/16/23 2:11 AM, Pushkar Deole wrote: > > Hi streams Dev community @matthias, @bruno > > > > Any inputs on above issue? Is this a bug in the streams library wherein > the > > input topic removed from streams processor topology, the underlying > > consumer group still reporting lag against those? > > > > On Wed, Aug 9, 2023 at 4:38 PM Pushkar Deole <pdeole2...@gmail.com> > wrote: > > > >> Hi All, > >> > >> I have a streams application with 3 instances with application-id set to > >> applicationV1. The application uses processor API with reading from > source > >> topics, processing the data and writing to destination topic. > >> Currently it consumes from 6 source topics however we don't need to > >> process data any more from 2 of those topics so we removed 2 topics from > >> the source topics list. We have configured Datadog dashboard to report > and > >> alert on consumer lag so after removing the 2 source topics and > deploying > >> application, we started getting several alerts about consumer lag on > >> applicationV1 consumer group which is underlying consumer group of the > >> streams application. When we looked at the consumer group from > kafka-cli, > >> we could see that the consumer group is reporting lag against the topics > >> removed from source topic list which is reflecting as increasing lag on > >> Datadog monitoring. > >> > >> Can someone advise if this is expected behavior? In my opinion, this is > >> not expected since streams application no more has those topics as part > of > >> source, it should not report lag on those. > >> > > >
