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https://issues.apache.org/jira/browse/HADOOP-4116?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Raghu Angadi updated HADOOP-4116:
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Description:
The number of threads are currently limited on datanodes. Once these threads
are occupied, DataNode does not accept any more requests (DOS). Recently we saw
a case where most of the 256 threads were waiting in
{{DataXceiver.replaceBlock()}} trying to acquire {{balancingSem}}. Since
rebalancing is (heavily) throttled, I would think this would be the common
case.
These operations waiting for active rebalancing threads to finish need not
take up a thread.
was:
The number of threads are currently limited on datanodes. Once these threads
are occupied, DataNode does not accept any more requests (DOS). Recently we saw
a case where most of the 256 threads were waiting in
{{DataXceiver.replaceBlock()}} trying to acquire {{balancingSem}}. Since
rebalancing is (heavily) throttled, I would think this would be the common
case.
These waiting threads need not take up a thread.
Summary: DataNode : idle rebalancing operations need not take up
threads. (was: DataNode : idle rebalancing threads need not take up threads.)
> DataNode : idle rebalancing operations need not take up threads.
> ----------------------------------------------------------------
>
> Key: HADOOP-4116
> URL: https://issues.apache.org/jira/browse/HADOOP-4116
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs
> Affects Versions: 0.17.0
> Reporter: Raghu Angadi
>
> The number of threads are currently limited on datanodes. Once these threads
> are occupied, DataNode does not accept any more requests (DOS). Recently we
> saw a case where most of the 256 threads were waiting in
> {{DataXceiver.replaceBlock()}} trying to acquire {{balancingSem}}. Since
> rebalancing is (heavily) throttled, I would think this would be the common
> case.
> These operations waiting for active rebalancing threads to finish need not
> take up a thread.
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