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https://issues.apache.org/jira/browse/KAFKA-3559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15242668#comment-15242668
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ASF GitHub Bot commented on KAFKA-3559:
---------------------------------------
GitHub user enothereska opened a pull request:
https://github.com/apache/kafka/pull/1223
KAFKA-3559: lazy initialisation of state stores
Instead of initialising state stores on init(), they are initialised on
first access.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/enothereska/kafka KAFKA-3559-rebalance
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/kafka/pull/1223.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1223
----
commit fa970d2126fc10bcba1748d2448ae3c3489e05e7
Author: Eno Thereska <eno.there...@gmail.com>
Date: 2016-04-15T08:52:34Z
Lazy initialization of state stores (on access, rather than all at once)
commit aebb365d04504cc0a5100715ccfd37a82b8b0298
Author: Eno Thereska <eno.there...@gmail.com>
Date: 2016-04-15T09:02:50Z
Check arguments
----
> 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: Bug
> Components: streams
> Reporter: Guozhang Wang
> Assignee: Eno Thereska
> Labels: architecture
> Fix For: 0.10.0.0
>
>
> 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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