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https://issues.apache.org/jira/browse/TEZ-4068?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16836066#comment-16836066
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Ying Han commented on TEZ-4068:
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Indeed in most cases a speculative attempt scheduled once a canCommit has been
issued would be cancelled before completion. I would like to mention though,
that there is a slight chance that an attempt can still fail after canCommit:
between invocation of TaskImpl#canCommit and the sending of
TaskAttemptCompletedEvent.
That being said, I do agree that speculative attempt scheduled after commit has
been initialized would be most likely wasted, and it is a reasonable
optimization to prevent that from happening. I would like to take on this JIRA
and has assigned it to myself, [~jeagles].
> Prevent new speculative attempt after task has issued canCommit to an attempt
> -
>
> Key: TEZ-4068
> URL: https://issues.apache.org/jira/browse/TEZ-4068
> Project: Apache Tez
> Issue Type: Improvement
>Reporter: Jonathan Eagles
>Priority: Major
>
> When a running attempt calls TaskImpl#canCommit through the taskUmbilical,
> the TaskImpl will issue a "go" if it is the first attempt to do so. Otherwise
> it will issue a "no-go". After commitAttempt is assigned is TaskImpl, no
> other attempt is allowed to succeed at that point. So a speculative attempt
> that is launched after commitAttempt is assigned can never finished before
> the original since is will allows be given a "no-go" in the canCommit
> response. In this jira, I propose to discuss disabling speculative attempts
> after commitAttempt has been assigned.
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