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https://issues.apache.org/jira/browse/OOZIE-616?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Virag Kothari updated OOZIE-616:
--------------------------------
Assignee: Kiran Nagasubramanian
> Moving action prepare FS execution to LauncherMapper
> ----------------------------------------------------
>
> Key: OOZIE-616
> URL: https://issues.apache.org/jira/browse/OOZIE-616
> Project: Oozie
> Issue Type: Improvement
> Reporter: Kiran Nagasubramanian
> Assignee: Kiran Nagasubramanian
> Fix For: 3.2.0
>
>
> 1) Motivations:
> ----------------
> a) Currently Oozie Server executes the Prepare logic before posting the
> Launcher job to Hadoop. If the launcher fails and the execution is retried by
> Hadoop automatically, the prepare logic is not re-executed. So, for
> Java/MR/Pig actions, if the launcher fails and it is retried by Hadoop
> automatically, the prepare logic is not executed again. Once the prepare
> logic execution is moved to the Launcher, the prepare logic is also
> re-executed during every retry.
> b) Heavy duty operations like copy that are currently not supported can be
> supported once the prepare logic has been moved to the Launcher.
> 2) Design choices for the proposed model:
> ------------------------------------------------
> a) Separate classes for different types of actions
> ---------------------------------------------------------
> The different types of actions like FS actions, HCat related actions, etc.
> can be grouped together in separate classes like FSActions, HCatActions, etc.
> b) Passing the prepare logic to the Launcher
> ---------------------------------------------------
> Launcher needs the Prepare XML block to execute the actions. Oozie server can
> write the XML block to a file on DFS and then the Launcher could read from
> there.
> c) Execution of actions through a "Driver"
> -----------------------------------------------
> The Launcher can pass the XML block to the Driver which parses the content
> and calls corresponding methods that are grouped in different classes.
> 3) Pros and Cons of the design change:
> --------------------------------------------
> a) User facing impacts:
> -------------------------
> i) At present: In case of prepare block failure, there is no impact on the
> retry of map reduce job since the prepare block would have got executed
> earlier itself. The impact is seen only when Launcher fails.
>
> As per the proposed design: When the prepare block fails it will impact the
> retry of the map reduce job.
>
> ii) At present: In the case of prepare block failure, the
> launcher mapper is not launched at all.
>
> As per the proposed design: The cost of executing the
> prepare block would go up since it requires the launch of a map only task.
> This is highly pronounced in case of failures
>
> Thanks a lot for all the input from Oozie team members.
> Please post your suggestions. Thanks.
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