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https://issues.apache.org/jira/browse/PHOENIX-5945?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chinmay Kulkarni updated PHOENIX-5945:
--------------------------------------
    Fix Version/s:     (was: 4.16.0)
                   4.17.0
                   4.16.1

> TaskRegionObserver can kick off the same task multiple times if SYSTEM.TASK 
> has split
> -------------------------------------------------------------------------------------
>
>                 Key: PHOENIX-5945
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-5945
>             Project: Phoenix
>          Issue Type: Bug
>    Affects Versions: 4.15.0
>            Reporter: Chinmay Kulkarni
>            Priority: Major
>             Fix For: 5.1.0, 4.16.1, 4.17.0
>
>
> We don't specify a split policy for 
> [SYSTEM.TASK|https://github.com/apache/phoenix/blob/5f9364db7e4925229704706e148e62f4cf4ec4c2/phoenix-core/src/main/java/org/apache/phoenix/query/QueryConstants.java#L381],
>  so by default it will be allowed to split. Now if SYSTEM.TASK spans multiple 
> regions, each region's 
> [postOpen|https://github.com/apache/phoenix/blob/5f9364db7e4925229704706e148e62f4cf4ec4c2/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/TaskRegionObserver.java#L137]
>  schedules the SelfHealingTask at the specified interval and so [each region 
> will run a FTS on the 
> table|https://github.com/apache/phoenix/blob/5f9364db7e4925229704706e148e62f4cf4ec4c2/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/TaskRegionObserver.java#L159]
>  and try to kick-off all the incomplete and non-failed tasks.
> This can lead to the same tasks being kicked off multiple times as a corner 
> race condition in spite of [this 
> check|https://github.com/apache/phoenix/blob/5f9364db7e4925229704706e148e62f4cf4ec4c2/phoenix-core/src/main/java/org/apache/phoenix/coprocessor/TaskRegionObserver.java#L187-L195]
>  (which is another FTS) and also lead to unnecessary extra load on the server.
> We do not explicitly outline that tasks need to be idempotent, so we should 
> handle this properly in the TaskRegionObserver so that each region is only 
> responsible for tasks lying within its boundaries.



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