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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3415) JobEndNotifier isnt synchronized, doesnt check state before acting
Date Thu, 22 May 2008 07:33:55 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3415?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12598933#action_12598933

Alejandro Abdelnur commented on HADOOP-3415:

I'm fine with such changes, as you claim the current implementation could have issues in a
testing environment.

Regarding #3, the queue should be initialized then on startNotifier() to ensure it's clean.

> JobEndNotifier isnt synchronized, doesnt check state before acting
> ------------------------------------------------------------------
>                 Key: HADOOP-3415
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3415
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.16.3
>            Reporter: Steve Loughran
>            Priority: Minor
> JobEndNotifier is pretty hazardous inside.
> 1. the static startNotifier isnt synchronized, and doesnt check for being already running
before it creates a new worker thread. It should be sycnhronized and a no-op if there is a
live thread.
> 2. stopNotifier() should be a no-op if already stopped. It MUST NOT call thread.interrupt()
in such a state, as thread may be null. 
> 3. the registerNotification method also assumes that the static queue is non null.
> Things would be a lot safer by making this class part of a JobTracker, not a singleton
with static methods, as then you could more safely make assumptions about object state. This
would not only eliminate a lot of reentrancy problems, but tie the life of the notifier to
that of its owner, the JobTracker.

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