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https://issues.apache.org/jira/browse/KAFKA-7985?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Guozhang Wang updated KAFKA-7985:
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Component/s: streams
> Cleanup AssignedTasks / AbstractTask logic
> ------------------------------------------
>
> Key: KAFKA-7985
> URL: https://issues.apache.org/jira/browse/KAFKA-7985
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Guozhang Wang
> Priority: Major
>
> Today the life time of a task is:
> created -> [initializeStateStores] ->
> restoring (writes to the initialized state stores) -> [initializeTopology] ->
> running -> [closeTopology] ->
> suspended -> [closeStateManager] ->
> dead
> And hence the assigned tasks contains the following non-overlapping sets :
> created, restoring, running, suspended, (dead tasks do no need to be
> maintained). Normally `created` should be empty since once a task is created
> it should move on transit to either restoring or running immediately. So
> whenever we are suspending tasks, we should go through these sets and act
> accordingly:
> 1. `created` and `suspended`: just check these two sets are always empty.
> 2. `running`: transit to `suspended`.
> 3. `restoring`: transite to `suspended`. But the difference here is that we
> do not need to close topology since it was not created yet at all; we just
> need to remember the restored position, and keep the restorers on hold
> instead of clearing all of them.
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