[jira] [Reopened] (HDFS-7964) Add support for async edit logging

["Zhe Zhang (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-7964?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Zhe Zhang reopened HDFS-7964:
-----------------------------

I think this'd be a very useful addition to branch-2.8 and branch-2.7. Especially since the patch has been used in 2.6 production cluster for a long time.

Attaching branch-2.8/branch-2.7 patches to verify with Jenkins.

> 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
>             Fix For: 2.9.0, 3.0.0-alpha1
>
>         Attachments: HDFS-7964-rebase.patch, HDFS-7964.patch, HDFS-7964.patch, HDFS-7964.patch, HDFS-7964.patch
>
>
> 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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