[jira] [Commented] (BOOKKEEPER-259) Create a topic manager using versioned write for leader election

["Ivan Kelly (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BOOKKEEPER-259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13412681#comment-13412681 ] 

Ivan Kelly commented on BOOKKEEPER-259:
---------------------------------------

Looks good. I have a couple of comments...
- MMTopicManager#ownerHubId is unused.
- MMGetOwnerOp#shouldClaim is never used
- Load data should be a protobuf message
- PubSubServer#instantiateTopicManager: The message should warn that this could cause scalability issues. Tense of use is incorrect also.
"Uses {} to store hedwig metadata, but uses zookeeper ephemeral znodes to store topic ownershop. Check your configuration as this could lead to scalability issues."

Once fixed it should be ready to go.
                
> Create a topic manager using versioned write for leader election
> ----------------------------------------------------------------
>
>                 Key: BOOKKEEPER-259
>                 URL: https://issues.apache.org/jira/browse/BOOKKEEPER-259
>             Project: Bookkeeper
>          Issue Type: Sub-task
>          Components: hedwig-server
>            Reporter: Sijie Guo
>            Assignee: Sijie Guo
>             Fix For: 4.2.0
>
>         Attachments: BOOKKEEPER-259.diff, BOOKKEEPER-259.diff_v2, BOOKKEEPER-259.diff_v3
>
>
> currently, ZkTopicManager use zookeeper ephemeral node to store the owner information of a topic. so the znode will disappear when the owner hub server is down, the leader election is quite simple based on this model.
> but for most key-value storage, there is no similar concepts like ephemeral node, but just providing versioned writes. so it would be better to provide a topic manager using versioned writes.

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