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From "Joydeep Sen Sarma (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (MAPREDUCE-2114) user finer grained locks in JT getCounters implementation
Date Tue, 12 Oct 2010 07:32:37 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-2114?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Joydeep Sen Sarma resolved MAPREDUCE-2114.
------------------------------------------

    Resolution: Duplicate

> user finer grained locks in JT getCounters implementation
> ---------------------------------------------------------
>
>                 Key: MAPREDUCE-2114
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2114
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobtracker
>            Reporter: Joydeep Sen Sarma
>
> We are bound on the JobTracker lock on our largest cluster. One pattern i have seen is
the following:
> - JT acquires JobTracker lock - but blocked on JIP lock:
> java.lang.Thread.State: BLOCKED (on object monitor)
> at org.apache.hadoop.mapred.JobInProgress.updateTaskStatus(JobInProgress.java:1028)
>   waiting to lock <0x00002aae21092ff8> (a org.apache.hadoop.mapred.JobInProgress)
> at org.apache.hadoop.mapred.JobTracker.updateTaskStatuses(JobTracker.java:4403)
> at org.apache.hadoop.mapred.JobTracker.processHeartbeat(JobTracker.java:3444)
>   locked <0x00002aab6ebb6640> (a org.apache.hadoop.mapred.JobTracker)
> - the JIP lock is typically held by a getcounters call:
>   locked <0x00002aaaf88beff8> (a org.apache.hadoop.mapred.Counters$Group)
> at org.apache.hadoop.mapred.Counters.incrAllCounters(Counters.java:445)
>   locked <0x00002aaaf88bb948> (a org.apache.hadoop.mapred.Counters)
> at org.apache.hadoop.mapred.JobInProgress.incrementTaskCounters(JobInProgress.java:1253)
> at org.apache.hadoop.mapred.JobInProgress.getCounters(JobInProgress.java:1240)
>   locked <0x00002aae21092ff8> (a org.apache.hadoop.mapred.JobInProgress)
> the solution seems simple. in order to summarize the counters for all tasks - we need
to only lock one task's counters at a time. we don't need to lock the entire job. 

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