[jira] [Updated] (AMBARI-18728) During cluster install, Components get timed out icon while starting

["Yusaku Sako (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AMBARI-18728?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yusaku Sako updated AMBARI-18728:
---------------------------------
    Reporter: Vivek Rathod  (was: Andrew Onischuk)

> During cluster install, Components get timed out icon while starting
> --------------------------------------------------------------------
>
>                 Key: AMBARI-18728
>                 URL: https://issues.apache.org/jira/browse/AMBARI-18728
>             Project: Ambari
>          Issue Type: Bug
>            Reporter: Vivek Rathod
>            Assignee: Andrew Onischuk
>             Fix For: 2.5.0
>
>         Attachments: AMBARI-18728.patch
>
>
> This was caused by a very tricky race-condition in the way python multiprocessing.thread works resulting in deadlock in ambari_agent.ActionQueue thread.
> The problem is the below flow:
> If this all these three get executed at the same time (a very rear occasion):
> 1. Process1 executes queue.get(False)
> 2. Process2 executes queue.put(largeObjectWhichTakesLongTimeToPut)
> 3. Someone kills Process2.
> This results in deadlock in process1 get. Which is caused by queue locks/semaphores to being released during put of process2.
> I have wrote a script test_race_condition.py to emulate this behaviour and indeed could reproduce this and test the fix for it.



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