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https://issues.apache.org/jira/browse/KAFKA-3559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15569915#comment-15569915
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Guozhang Wang commented on KAFKA-3559:
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[~enothereska] If you feel this suggestion deserve another ticket, feel free to
create a separate one and since with KIP-4 there is little difference between
initializing in the rebalance callback v.s. after the rebalance completes, we
can close this ticket if you think so.
> Task creation time taking too long in rebalance callback
> --------------------------------------------------------
>
> Key: KAFKA-3559
> URL: https://issues.apache.org/jira/browse/KAFKA-3559
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Guozhang Wang
> Assignee: Eno Thereska
> Labels: architecture
> Fix For: 0.10.2.0
>
>
> Currently in Kafka Streams, we create stream tasks upon getting newly
> assigned partitions in rebalance callback function {code} onPartitionAssigned
> {code}, which involves initialization of the processor state stores as well
> (including opening the rocksDB, restore the store from changelog, etc, which
> takes time).
> With a large number of state stores, the initialization time itself could
> take tens of seconds, which usually is larger than the consumer session
> timeout. As a result, when the callback is completed, the consumer is already
> treated as failed by the coordinator and rebalance again.
> We need to consider if we can optimize the initialization process, or move it
> out of the callback function, and while initializing the stores one-by-one,
> use poll call to send heartbeats to avoid being kicked out by coordinator.
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