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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2141) Remove NameNode roles Active and Standby (they become states)
Date Wed, 20 Jul 2011 15:50:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13068448#comment-13068448

Konstantin Shvachko commented on HDFS-2141:

Guys, you are changing the meaning of the role and calling it state. I intentionally tried
to avoid using "state" while designing BackupNode, because word state is highly overloaded.

Yes original NameNode was not designed for HA, but BackupNode was. Therefore the roles.

Please read here:
"[Standby node (SN) - a name-node in "standby" state.|https://issues.apache.org/jira/secure/attachment/12400631/StreamEditsToBN.pdf]
Standby is a backup node, which is able to take over the active role if the current active

Role is not a name of the daemon its the what defines the functionality of NN. NN functions
as single active node, but cannot checkpoint. BN keeps the copy of the namepsace, but cannot
turn into standby. CN creates checkpoints but does not keep the namespace. SBN can turn into
What is wrong with current terminology and why it needs to be changed?

Todd, could we please stay on the topic and not diverge to inheritance issues. I agree NN
should evolve into a single class for all nodes, but lets do it somewhere else.

> Remove NameNode roles Active and Standby (they become states)
> -------------------------------------------------------------
>                 Key: HDFS-2141
>                 URL: https://issues.apache.org/jira/browse/HDFS-2141
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: name-node
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>             Fix For: 0.23.0
>         Attachments: HDFS-2141.1.patch, HDFS-2141.patch
> In HDFS, following roles are supported in NameNodeRole: ACTIVE, BACKUP, CHECKPOINT and
> Active and Standby are the state of the NameNode. While Backup and CheckPoint are the
name/role of the daemons that are started. This mixes up the run time state of NameNode with
the daemon role. I propose changing the NameNodeRole to: NAMENODE, BACKUP, CHECKPOINT. HDFS-1974
will introduce the states active and standby to the daemon that is running in the role NAMENODE.

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