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https://issues.apache.org/jira/browse/KAFKA-16514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17842765#comment-17842765
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Lianet Magrans commented on KAFKA-16514:
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Just to answer the question above:
{quote}what is the purpose of -2 code? In the end, not sending any request,
with a large enough session timeout, no rebalance would be triggered anyway?
What does change is we send -2 instead of just not sending any leaver group
request on close()?{quote}
The purpose is just to set the intention explicitly at the protocol level (and
not assume it). This is mainly to allow for richer semantics around the static
membership leave in the future. It does not make a difference at the moment
(over not sending the leave group), but it does allow to cleanly extend the
current logic if we ever want to, and allow static members to leave permanently
by sending a -1 epoch on the leave group. That would effectively allow to
remove a static members from a group (which can only be achieved now either
waiting for the session timeout to expire, or via the admin api)
Anyways, that's just food for thought for now. The KIP extending the consumer
close with options seems sensible to solve the current situation, and would
align nicely with any future extension of the static leave semantics if we ever
go down that path.
> Kafka Streams: stream.close(CloseOptions) does not respect options.leaveGroup
> flag.
> -----------------------------------------------------------------------------------
>
> Key: KAFKA-16514
> URL: https://issues.apache.org/jira/browse/KAFKA-16514
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 3.7.0
> Reporter: Sal Sorrentino
> Priority: Minor
>
> Working with Kafka Streams 3.7.0, but may affect earlier versions as well.
> When attempting to shutdown a streams application and leave the associated
> consumer group, the supplied `leaveGroup` option seems to have no effect.
> Sample code:
> {code:java}
> CloseOptions options = new CloseOptions().leaveGroup(true);
> stream.close(options);{code}
> The expected behavior here is that the group member would shutdown and leave
> the group, immediately triggering a consumer group rebalance. In practice,
> the rebalance happens after the appropriate timeout configuration has expired.
> I understand the default behavior in that there is an assumption that any
> associated StateStores would be persisted to disk and that in the case of a
> rolling restart/deployment, the rebalance delay may be preferable. However,
> in our application we are using in-memory state stores and standby replicas.
> There is no benefit in delaying the rebalance in this setup and we are in
> need of a way to force a member to leave the group when shutting down.
> The workaround we found is to set an undocumented internal StreamConfig to
> enforce this behavior:
> {code:java}
> props.put("internal.leave.group.on.close", true);
> {code}
> To state the obvious, this is less than ideal.
> Additional configuration details:
> {code:java}
> Properties props = new Properties();
> props.put(StreamsConfig.APPLICATION_ID_CONFIG, "someApplicationId");
> props.put(
> StreamsConfig.BOOTSTRAP_SERVERS_CONFIG,
> "localhost:9092,localhost:9093,localhost:9094");
> props.put(StreamsConfig.REPLICATION_FACTOR_CONFIG, 3);
> props.put(StreamsConfig.NUM_STANDBY_REPLICAS_CONFIG, 1);
> props.put(StreamsConfig.NUM_STREAM_THREADS_CONFIG, numProcessors);
> props.put(StreamsConfig.PROCESSING_GUARANTEE_CONFIG,
> StreamsConfig.EXACTLY_ONCE_V2);{code}
>
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