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https://issues.apache.org/jira/browse/IMPALA-9140?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16972037#comment-16972037
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Quanlong Huang commented on IMPALA-9140:
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{quote}I think the PriorityQueue solution actually makes sense here. The starve
situation Quanlong Huang mentioned also exist in the current implementation.
Because we can get a lot of new sync load requests and there is no guarantee
when will an idle thread in tblLoadingPool_ pick up an async task.
{quote}
[~jiawei.wang], I think you may miss the fact that tblLoadingPool_ is a
FixedThreadPool that uses a LinkedBlockingQueue to queue the submitted tasks.
So the task being submitted first will be executed first. Async load requests
won't starve since there are always _numLoadingThreads_ of tasks of them
submitted. New sync load requests are submitted later.
> Get rid of the unnecessary load submitter thread pool in tblLoadingMgr
> ----------------------------------------------------------------------
>
> Key: IMPALA-9140
> URL: https://issues.apache.org/jira/browse/IMPALA-9140
> Project: IMPALA
> Issue Type: Bug
> Reporter: Vihang Karajgaonkar
> Priority: Major
>
> This JIRA is created as a followup on the discussion on
> https://gerrit.cloudera.org/#/c/14611 related to various pools used for
> loading tables.
> It looks like there are 2 pools of threads both of the size
> {{num_metadata_loading_threads}}. One pool is used to submit the load
> requests to another pool {{tblLoadingPool_}} which does the actual loading of
> the tables. I think we can get rid of the pool which submits the tasks since
> it is not very time-consuming operation and can be done synchronously (all it
> needs to do submit the task in the queue in the front or back based on
> whether its a prioritized load or background load). This will simplify the
> loading code and reduce unnecessary number of threads being created by
> {{TblLoadingMgr}}
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