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https://issues.apache.org/jira/browse/KAFKA-15116?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17739920#comment-17739920
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David Gammon commented on KAFKA-15116:
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# The internal store is shared across stream threads. There is a consumer
outside of kafka streams that is reading "read_committed" messages that
populates the store and unblocks the processor.
# In this context I'm talking about eos and the transaction being committed
and therefore the consumer being able to read the "read_committed" message.
I think ultimately our problem is that the stream thread carries on processing
messages during a rebalance but does not complete them (transaction commit).
Even though pausing processing during a rebalance probably shouldn't be default
behaviour it would be ideal for us if it were configurable. Pausing consumption
feels valid especially when there is a dependency between messages with the
same partion key?
> Kafka Streams processing blocked during rebalance
> -------------------------------------------------
>
> Key: KAFKA-15116
> URL: https://issues.apache.org/jira/browse/KAFKA-15116
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 3.5.0
> Reporter: David Gammon
> Priority: Major
>
> We have a Kafka Streams application that simply takes a messages, processes
> it and then produces an event out the other side. The complexity is that
> there is a requirement that all events with the same partition key must be
> committed before the next message is processed.
> This works most of the time flawlessly but we have started to see problems
> during deployments where the first message blocks the second message during a
> rebalance because the first message isn’t committed before the second message
> is processed. This ultimately results in transactions timing out and more
> rebalancing.
> We’ve tried lots of configuration to get the behaviour we require with no
> luck. We’ve now put in a temporary fix so that Kafka Streams works with our
> framework but it feels like this might be a missing feature or potentially a
> bug.
> +Example+
> Given:
> * We have two messages (InA and InB).
> * Both messages have the same partition key.
> * A rebalance is in progress so streams is no longer able to commit.
> When:
> # Message InA -> processor -> OutA (not committed)
> # Message InB -> processor -> blocked because #1 has not been committed
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