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https://issues.apache.org/jira/browse/MAPREDUCE-6144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14224217#comment-14224217
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zhihai xu commented on MAPREDUCE-6144:
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Hi [~xgong], Yes, you are right. mapContainerNeeds will be empty if
MAP_SPECULATIVE is disabled, If mapContainerNeeds is empty,
maybeScheduleAMapSpeculation will return 0. Same for reduceContainerNeeds and
maybeScheduleAReduceSpeculation,
because SpeculatorEventDispatcher in MRAppMaster handles
TASK_CONTAINER_NEED_UPDATE SpeculatorEvent based on task type, MAP_SPECULATIVE
configuration and REDUCE_SPECULATIVE configuration.
thanks for the review.
zhihai
> DefaultSpeculator always add both MAP and REDUCE Speculative task even
> MAP_SPECULATIVE or REDUCE_SPECULATIVE is disabled.
> -------------------------------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-6144
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6144
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2
> Affects Versions: 2.5.1
> Reporter: zhihai xu
> Assignee: zhihai xu
> Attachments: MAPREDUCE-6144.000.patch, MAPREDUCE-6144.001.patch
>
>
> DefaultSpeculator always add both MAP and REDUCE Speculative task even
> MAP_SPECULATIVE or REDUCE_SPECULATIVE is disabled.
> If both MAP_SPECULATIVE and REDUCE_SPECULATIVE are disabled,
> DefaultSpeculator won't start.
> The issue will happen if only one of MAP_SPECULATIVE and REDUCE_SPECULATIVE
> is enabled, both MAP and REDUCE Speculative task are generate.
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