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https://issues.apache.org/jira/browse/HADOOP-2119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12561091#action_12561091
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Amar Kamat commented on HADOOP-2119:
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Some doubts,
{quote}
+ synchronized (JobTracker.this) {
+ for(count=0;count<jlist.size();count++) {
{quote}
this indicates that the array is scanned with the lock acquired. Is it
scalable? Since the array size could be huge. Locking the JobTracker for this
duration could be a performance hit or am I missing something? Currently only
one task is considered at a time thus freeing the locks in between and thus the
JobTracker progresses in between.
> JobTracker becomes non-responsive if the task trackers finish task too fast
> ---------------------------------------------------------------------------
>
> Key: HADOOP-2119
> URL: https://issues.apache.org/jira/browse/HADOOP-2119
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.16.0
> Reporter: Runping Qi
> Priority: Blocker
> Fix For: 0.16.0
>
> Attachments: hadoop-2119.patch, hadoop-jobtracker-thread-dump.txt
>
>
> I ran a job with 0 reducer on a cluster with 390 nodes.
> The mappers ran very fast.
> The jobtracker lacks behind on committing completed mapper tasks.
> The number of running mappers displayed on web UI getting bigger and bigger.
> The jos tracker eventually stopped responding to web UI.
> No progress is reported afterwards.
> Job tracker is running on a separate node.
> The job tracker process consumed 100% cpu, with vm size 1.01g (reach the heap
> space limit).
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