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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5176) Preemptable annotations (to support preemption in MR)
Date Mon, 20 May 2013 20:41:16 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5176?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13662339#comment-13662339

Karthik Kambatla commented on MAPREDUCE-5176:

bq. what we envisioned for mapreduce is that and advanced user that have a stateful UDF can
mark it as @Preemptable and override the default save to checkpoint logic to include the portion
of state he/she cares about.

While that is perfectly fine for a first draft solution, a user might prefer to get feedback
when they annotate @Preemptable without fully understanding the consequences. Assuming @Stateless
is also added, the preemption code can warn the user that they have annotated @Preemptable
without @Stateless and that they are expected to implement/override the checkpoint logic.

> Preemptable annotations (to support preemption in MR)
> -----------------------------------------------------
>                 Key: MAPREDUCE-5176
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5176
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: mrv2
>            Reporter: Carlo Curino
>            Assignee: Carlo Curino
>         Attachments: MAPREDUCE-5176.1.patch, MAPREDUCE-5176.patch
> Proposing a patch that introduces a new annotation @Preemptable that represents to the
framework property of user-supplied classes (e.g., Reducer, OutputCommiter). The intended
semantics is that a tagged class is safe to be preempted between invocations. 
> (this is in spirit similar to the Output Contracts of [Nephele/PACT | https://stratosphere.eu/sites/default/files/papers/ComparingMapReduceAndPACTs_11.pdf])

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