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https://issues.apache.org/jira/browse/HDFS-2185?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13241500#comment-13241500
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Bikas Saha commented on HDFS-2185:
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I am surprised that only an inElection state suffices instead of an
inElectionActive and inElectionStandby. Arent there actions that need to be
performed differently when the FC is active or standby?
There is no state transition dependent on the result of transitionToActive().
If transitionToActive on NN fails then FC should quitElection IMO. Currently,
it quits election only on HM events. Same for transitionToStandby on NN. If
that fails then should we not do something?
Which state is performing fencing? The state machine does not show fencing? Is
it happening in the the HAService?
IMO - this state diagram has to be more clear about handling the
success/failure of each operation. That is key to determining the robustness of
FC. FC needs to be super robust by design right?
> HA: HDFS portion of ZK-based FailoverController
> -----------------------------------------------
>
> Key: HDFS-2185
> URL: https://issues.apache.org/jira/browse/HDFS-2185
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: auto-failover, ha
> Affects Versions: 0.24.0, 0.23.3
> Reporter: Eli Collins
> Assignee: Todd Lipcon
> Attachments: Failover_Controller.jpg, hdfs-2185.txt, hdfs-2185.txt,
> hdfs-2185.txt, hdfs-2185.txt, zkfc-design.pdf, zkfc-design.pdf,
> zkfc-design.tex
>
>
> This jira is for a ZK-based FailoverController daemon. The FailoverController
> is a separate daemon from the NN that does the following:
> * Initiates leader election (via ZK) when necessary
> * Performs health monitoring (aka failure detection)
> * Performs fail-over (standby to active and active to standby transitions)
> * Heartbeats to ensure the liveness
> It should have the same/similar interface as the Linux HA RM to aid
> pluggability.
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