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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-1974) HA: Introduce active and standby states to the namenode
Date Mon, 08 Aug 2011 23:58:28 GMT

     [ https://issues.apache.org/jira/browse/HDFS-1974?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Suresh Srinivas updated HDFS-1974:
----------------------------------

    Attachment: HDFS-1974.3.patch

Thanks for the comments. I have addressed most of them in the new patch.

bq. public static boolean isHAEnabled(Configuration conf) - is the intention that this will
return true if HA is enabled on the cluster? yes

bq. this.state = DFSUtil.isHAEnabled(conf) ? ACTIVE_STATE : STANDBY_STATE; - should probably
be replaced with a TODO. It's obviously not reasonable to have both NNs start as active just
because HA is enabled. There needs to be some leader determination.
I meant !isHAEnabled, then retain the older functionality. New patch addresses it.

bq. UnsupportedActionException seems redundant with o.a.h.ipc.StandbyException.
How do you handle operations related to checkpointing and journaling that namenode in it's
various states/roles cannot satisfy?

Further we need to think if StandbyException should be at IPC layer? Is this not Service related
exception?

bq. I don't understand the purpose of having both HAState.setState and HAState.(standbyToActive|activeToStandby).
Shouldn't just setState be sufficient?
Setting a state involves multiple steps - that existing current state and entering a new state.
standbyToActive and activeToStandby are interface methods.

bq. In HAState.setState, you have exitState(nn); s.enterState(nn);. What state should the
NN be considered to be in between these calls?
exitState does the cleanup required for exiting a state, with in the state. I have made a
change to set the state of NN before enterState.


> HA: Introduce active and standby states to the namenode
> -------------------------------------------------------
>
>                 Key: HDFS-1974
>                 URL: https://issues.apache.org/jira/browse/HDFS-1974
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: name-node
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>         Attachments: HDFS-1974.1.patch, HDFS-1974.2.patch, HDFS-1974.3.patch, HDFS-1974.patch
>
>
> Currently namenode supports active, secondary and backup roles. To support namenode high
availability, active and standby states are needed. Note that this is different from the existing
notion of namenode role, where a namenode cannot transition from one role to the other.

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