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https://issues.apache.org/jira/browse/KAFKA-12500?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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A. Sophie Blee-Goldman reassigned KAFKA-12500:
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Assignee: A. Sophie Blee-Goldman
> Cache memory is leaked after removing/replacing a StreamThread
> --------------------------------------------------------------
>
> Key: KAFKA-12500
> URL: https://issues.apache.org/jira/browse/KAFKA-12500
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Reporter: A. Sophie Blee-Goldman
> Assignee: A. Sophie Blee-Goldman
> Priority: Blocker
> Fix For: 2.8.0
>
>
> We currently leak the memory given to a StreamThread for its cache after it
> gets shutdown due to being removed or replaced.
> Removal:
> If the StreamThread is removing itself, or if a thread is being removed by an
> external caller but fails to shutdown within the allotted time, it won't be
> removed from the `threads` list to avoid freeing up it's thread id while
> still running. If the thread hasn't reached the DEAD state when we resize the
> cache, the new cache size per thread is computed based on the number of live
> threads, which includes the removed thread at this point.
> Replacement:
> When a thread is replaced, we first shutdown that thread but hold off on
> removing it from the threads list until it's DEAD. Immediately after the
> shutdown we call addStreamThread to start up a new thread, which resizes the
> cache according to num-live-threads + 1.
> In both of these cases, the cache memory of the shutting down thread won't be
> made available to the remaining threads.
> Note: in general this leak may not be permanent, as a subsequent event once
> the thread has reached DEAD and been removed from the threads list will cause
> it's memory to be released. OF course if the subsequent event is another
> thread removal or replacement, then we just have a new memory leak.
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