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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-2177) The wait for spill completion should call Condition.awaitNanos(long nanosTimeout)
Date Mon, 08 Nov 2010 16:27:13 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12929619#action_12929619
] 

Arun C Murthy commented on MAPREDUCE-2177:
------------------------------------------

bq.  calling progress() during the merge- at least ensures that the task is doing work; reporting
progress from a thread that isn't actually proceeding is broken. Isn't progress already reported
during the merge? Can you provide more detail on the environment where you're observing this?

Chris, we've seen this at Y! too, this might just be a bug in progress reporting during the
merge.

> The wait for spill completion should call Condition.awaitNanos(long nanosTimeout)
> ---------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-2177
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2177
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: tasktracker
>    Affects Versions: 0.20.2
>            Reporter: Ted Yu
>
> We sometimes saw maptask timeout in cdh3b2. Here is log from one of the maptasks:
> 2010-11-04 10:34:23,820 INFO org.apache.hadoop.mapred.MapTask: Spilling map output: buffer
full= true
> 2010-11-04 10:34:23,820 INFO org.apache.hadoop.mapred.MapTask: bufstart = 119534169;
bufend = 59763857; bufvoid = 298844160
> 2010-11-04 10:34:23,820 INFO org.apache.hadoop.mapred.MapTask: kvstart = 438913; kvend
= 585320; length = 983040
> 2010-11-04 10:34:41,615 INFO org.apache.hadoop.mapred.MapTask: Finished spill 3
> 2010-11-04 10:35:45,352 INFO org.apache.hadoop.mapred.MapTask: Spilling map output: buffer
full= true
> 2010-11-04 10:35:45,547 INFO org.apache.hadoop.mapred.MapTask: bufstart = 59763857; bufend
= 298837899; bufvoid = 298844160
> 2010-11-04 10:35:45,547 INFO org.apache.hadoop.mapred.MapTask: kvstart = 585320; kvend
= 731585; length = 983040
> 2010-11-04 10:45:41,289 INFO org.apache.hadoop.mapred.MapTask: Finished spill 4
> Note how long the last spill took.
> In MapTask.java, the following code waits for spill to finish:
> while (kvstart != kvend) { reporter.progress(); spillDone.await(); }
> In trunk code, code is similar.
> There is no timeout mechanism for Condition.await(). In case the SpillThread takes long
before calling spillDone.signal(), we would see timeout.
> Condition.awaitNanos(long nanosTimeout) should be called.

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