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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-7964) Add support for async edit logging
Date Tue, 16 Feb 2016 18:40:18 GMT

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

Jing Zhao updated HDFS-7964:
----------------------------
    Attachment: HDFS-7964-rebase.patch

There are actually another "//if(LOG.isDebugEnabled)" in the patch. Changed it to
{code}
      if (LOG.isDebugEnabled()) {
        LOG.debug("logSync " + edit);
      }
{code}

Could you please check if the rebased patch looks good to you, [~daryn] and [~kihwal]?

> 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
>         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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