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https://issues.apache.org/jira/browse/HDFS-7964?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daryn Sharp updated HDFS-7964:
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Description:
Edit logging is a major source of contention within the NN. LogEdit is called
within the namespace write log, while logSync is called outside of the lock to
allow greater concurrency. The handler thread remains busy until logSync
returns to provide the client with a durability guarantee for the response.
Write heavy RPC load and/or slow IO causes handlers to stall in logSync.
Although the write lock is not held, readers are limited/starved and the call
queue fills. Combining an edit log thread with postponed RPC responses from
HADOOP-10300 will provide the same durability guarantee but immediately free up
the handlers.
was:
Edit logging is a major source of contention within the NN. LogEdit is called
within the namespace write log, while logSync is called outside of the lock to
allow greater concurrency. The handler thread remains busy until logSync
returns to provide the client with a durability guarantee for the response.
Write heavy RPC load and/or slow IO causes handlers to stall in logSync.
Although the write lock is not held, readers are limited/starved and the call
queue fills. Combining an edit log thread with postponed RPC responses from
HADOOP-9953 will provide the same durability guarantee but immediately free up
the handlers.
> Add support for async edit logging
> ----------------------------------
>
> Key: HDFS-7964
> URL: https://issues.apache.org/jira/browse/HDFS-7964
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Affects Versions: 2.0.2-alpha
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
>
> Edit logging is a major source of contention within the NN. LogEdit is
> called within the namespace write log, while logSync is called outside of the
> lock to allow greater concurrency. The handler thread remains busy until
> logSync returns to provide the client with a durability guarantee for the
> response.
> Write heavy RPC load and/or slow IO causes handlers to stall in logSync.
> Although the write lock is not held, readers are limited/starved and the call
> queue fills. Combining an edit log thread with postponed RPC responses from
> HADOOP-10300 will provide the same durability guarantee but immediately free
> up the handlers.
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