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From "Amit Anand (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-10665) Provide a way to add a new Journalnode to an existing quorum
Date Wed, 20 Jul 2016 23:45:20 GMT
Amit Anand created HDFS-10665:

             Summary: Provide a way to add a new Journalnode to an existing quorum
                 Key: HDFS-10665
                 URL: https://issues.apache.org/jira/browse/HDFS-10665
             Project: Hadoop HDFS
          Issue Type: New Feature
          Components: ha, hdfs, journal-node
            Reporter: Amit Anand

In current implementation of {{HDFS}} {{HA}} using {{QJOURNAL}} there is no way to add a new
{{Journalnode(JN)}} to an existing {{JN}} quorum or reinstall a failed {{JN}} machine.

The current process to populate {{JN}} directories is:
* Start {{JN}} daemons on multiple machines (usually an odd number 3 or 5)
* Shutdown {{Namenode}}
* Issue {{hdfs namenode -initializeSharedEdits}} - This will populate {{JN}}

After {{JN}} are populated; if a machine, after hardware failure, is reinstalled or a new
set of machines are added to expand the {{JN}} quorum the new {{JN}} machines will not be
populated by {{NameNode}} without following the current process that is described above. 

The current process causes downtime on a 24x7 operation cluster if {{JN}} needs any maintenance.

Although, one can follow steps given below to work around the issue described above:
1. Install a new {{JN}} or reinstall an existing {{JN}} machine.
2. Created the required {{JN}} directory structure
3. Copy {{VERSION}} file from an existing {{JN}} to {{JN's}} {{current}} directory
4. Manually create {{paxos}} directory under {{JN's}} {{current}} directory
5. Start the {{JN}} daemon.
6. Add new set of {{JNs}} to {{hdfs-site.xml}} and restart {{NN}}

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