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https://issues.apache.org/jira/browse/ZOOKEEPER-1080?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13048713#comment-13048713
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Aaron T. Myers commented on ZOOKEEPER-1080:
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Thanks a lot for posting this, Eric.
bq. Upon election, support creating a znode that indicates "ACK" of election
and provide a configurable data payload.
This I think would be potentially helpful for this library to be useful in
support of NN HA, since this configurable payload would likely be used to
indicate the hostname/address/identifier of the currently active NN.
bq. Write javadoc.
Specifically, I think it would be very useful to document the guarantees with
respect to which notification events occur when. For example, "an ELECTED_START
event will always correspond to exactly one later ELECTED_COMPLETE event," etc.
> Provide a Leader Election framework based on Zookeeper receipe
> --------------------------------------------------------------
>
> Key: ZOOKEEPER-1080
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1080
> Project: ZooKeeper
> Issue Type: New Feature
> Components: contrib
> Affects Versions: 3.3.2
> Reporter: Hari A V
> Attachments: LeaderElectionService.pdf, zookeeper-leader-0.0.1.tar.gz
>
>
> Currently Hadoop components such as NameNode and JobTracker are single point
> of failure.
> If Namenode or JobTracker goes down, there service will not be available
> until they are up and running again. If there was a Standby Namenode or
> JobTracker available and ready to serve when Active nodes go down, we could
> have reduced the service down time. Hadoop already provides a Standby
> Namenode implementation which is not fully a "hot" Standby.
> The common problem to be addressed in any such Active-Standby cluster is
> Leader Election and Failure detection. This can be done using Zookeeper as
> mentioned in the Zookeeper recipes.
> http://zookeeper.apache.org/doc/r3.3.3/recipes.html
> +Leader Election Service (LES)+
> Any Node who wants to participate in Leader Election can use this service.
> They should start the service with required configurations. The service will
> notify the nodes whether they should be started as Active or Standby mode.
> Also they intimate any changes in the mode at runtime. All other complexities
> can be handled internally by the LES.
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