[jira] [Created] (HDFS-4923) Save namespace when the namenode is stopped

["Suresh Srinivas (JIRA)" <ji...@apache.org>]

Suresh Srinivas created HDFS-4923:
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             Summary: Save namespace when the namenode is stopped
                 Key: HDFS-4923
                 URL: https://issues.apache.org/jira/browse/HDFS-4923
             Project: Hadoop HDFS
          Issue Type: Improvement
    Affects Versions: 3.0.0
            Reporter: Suresh Srinivas
            Assignee: Suresh Srinivas


In rare instances the namenode fails to load editlog due to corruption during startup. This has more severe impact if editlog segment to be checkpointed has corruption, as checkpointing fails because the editlog with corruption cannot be consumed. If an administrator does not notice this and address it by saving the namespace, recovering the namespace would involve complex file editing, using previous backups or losing last set of modifications.

The other issue that also happens frequently is, checkpointing fails and has not happened for a long time, resulting in long editlogs and even corrupt editlogs.

To handle these issues, when namenode is stopped, we can put it in safemode and save the namespace, before the process is shutdown. As an added benefit, the namenode restart would be faster, given there is no editlog to consume.

What do folks think?

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