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https://issues.apache.org/jira/browse/HDFS-2141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13068484#comment-13068484
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Suresh Srinivas commented on HDFS-2141:
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> 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.
I think state is more appropriate word - from state machines perspective. What
I am building is indeed state machine for HA.
> 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.
This is what I intend to do by introducing states in NameNode. Role as an
abstraction, in my opinion, is what caused the inheritance mess.
> 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 STANDBY.
> 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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