[ https://issues.apache.org/jira/browse/KAFKA-6106?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Guozhang Wang updated KAFKA-6106:
---------------------------------
Labels: newbie++ (was: )
> Postpone normal processing of tasks within a thread until restoration of all tasks have
completed
> -------------------------------------------------------------------------------------------------
>
> Key: KAFKA-6106
> URL: https://issues.apache.org/jira/browse/KAFKA-6106
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Affects Versions: 0.11.0.1, 1.0.0
> Reporter: Guozhang Wang
> Labels: newbie++
>
> Let's say a stream thread hosts multiple tasks, A and B. At the very beginning when A
and B are assigned to the thread, the thread state is {{TASKS_ASSIGNED}}, and the thread start
restoring these two tasks during this state using the restore consumer while using normal
consumer for heartbeating.
> If task A's restoration has completed earlier than task B, then the thread will start
processing A immediately even when it is still in the {{TASKS_ASSIGNED}} phase. But processing
task A will slow down restoration of task B since it is single-thread. So the thread's transition
to {{RUNNING}} when all of its assigned tasks have completed restoring and now can be processed
will be delayed.
> Note that the streams instance's state will only transit to {{RUNNING}} when all of its
threads have transit to {{RUNNING}}, so the instance's transition will also be delayed by
this scenario.
> We'd better to not start processing ready tasks immediately, but instead focus on restoration
during the {{TASKS_ASSIGNED}} state to shorten the overall time of the instance's state transition.
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