[
https://issues.apache.org/jira/browse/MAPREDUCE-4607?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Bikas Saha updated MAPREDUCE-4607:
----------------------------------
Status: Patch Available (was: Open)
> Race condition in ReduceTask completion can result in Task being incorrectly
> failed
> -----------------------------------------------------------------------------------
>
> Key: MAPREDUCE-4607
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4607
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 2.0.0-alpha
> Reporter: Bikas Saha
> Assignee: Bikas Saha
> Attachments: MAPREDUCE-4607.1.patch, MAPREDUCE-4607.2.patch,
> MAPREDUCE-4607.3.patch, MAPREDUCE-4607.4.patch, MAPREDUCE-4607.patch
>
>
> Problem reported by chackaravarthy in MAPREDUCE-4252
> This problem has been handled when speculative task launched for map task and
> other attempt got failed (not killed)
> Can the similar kind of scenario can happen in case of reduce task?
> Consider the following scenario for reduce task in case of speculation (one
> attempt got killed):
> 1. A task attempt is started.
> 2. A speculative task attempt for the same task is started.
> 3. The first task attempt completes and causes the task to transition to
> SUCCEEDED.
> 4. Then speculative task attempt will be killed because of the completion of
> first attempt.
> As a result, internal error will be thrown from this attempt
> (TaskImpl.MapRetroactiveKilledTransition) and hence task attempt failure
> leads to job failure.
> TaskImpl.MapRetroactiveKilledTransition
> if (!TaskType.MAP.equals(task.getType())) {
> LOG.error("Unexpected event for REDUCE task " + event.getType());
> task.internalError(event.getType());
> }
> So, do we need to have following code in MapRetroactiveKilledTransition also
> just like in MapRetroactiveFailureTransition.
> if (event instanceof TaskTAttemptEvent) {
> TaskTAttemptEvent castEvent = (TaskTAttemptEvent) event;
> if (task.getState() == TaskState.SUCCEEDED &&
> !castEvent.getTaskAttemptID().equals(task.successfulAttempt)) {
> // don't allow a different task attempt to override a previous
> // succeeded state
> return TaskState.SUCCEEDED;
> }
> }
> please check whether this is a valid case and give your suggestion.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
