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https://issues.apache.org/jira/browse/FLINK-10333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16923170#comment-16923170
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TisonKun edited comment on FLINK-10333 at 9/5/19 8:17 AM:
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{{LeaderServer}} is regarded as a prerequisite for new high-availability
services, otherwise we have to implement embedded one which should not be
required as design(see also
[here|https://lists.apache.org/x/thread.html/0da7ff1f985125f5f0f16b15cd1b6617f68d15cf11c421245071a485@%3Cdev.flink.apache.org%3E])
and live with the inconsistency views/apis between different
implementation(see concerns about retrieve JobMaster address above).
We can start a separated thread to handle its details and implementation if we
reach a consensus here. It would be cleanly individually integrated in current
codebase.
was (Author: tison):
Details and implementation of {{LeaderServer}} is regarded as a prerequisite
for new high-availability services, otherwise we have to implement embedded one
which should not be required as design(see also
[here|https://lists.apache.org/x/thread.html/0da7ff1f985125f5f0f16b15cd1b6617f68d15cf11c421245071a485@%3Cdev.flink.apache.org%3E])
and live with the inconsistency views/apis between different
implementation(see concerns about retrieve JobMaster address above).
We can start a separated thread to handle it if we reach a consensus here. It
would be cleanly individually integrated in current codebase.
> Rethink ZooKeeper based stores (SubmittedJobGraph, MesosWorker,
> CompletedCheckpoints)
> -------------------------------------------------------------------------------------
>
> Key: FLINK-10333
> URL: https://issues.apache.org/jira/browse/FLINK-10333
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Coordination
> Affects Versions: 1.5.3, 1.6.0, 1.7.0
> Reporter: Till Rohrmann
> Priority: Major
> Attachments: screenshot-1.png
>
>
> While going over the ZooKeeper based stores
> ({{ZooKeeperSubmittedJobGraphStore}}, {{ZooKeeperMesosWorkerStore}},
> {{ZooKeeperCompletedCheckpointStore}}) and the underlying
> {{ZooKeeperStateHandleStore}} I noticed several inconsistencies which were
> introduced with past incremental changes.
> * Depending whether {{ZooKeeperStateHandleStore#getAllSortedByNameAndLock}}
> or {{ZooKeeperStateHandleStore#getAllAndLock}} is called, deserialization
> problems will either lead to removing the Znode or not
> * {{ZooKeeperStateHandleStore}} leaves inconsistent state in case of
> exceptions (e.g. {{#getAllAndLock}} won't release the acquired locks in case
> of a failure)
> * {{ZooKeeperStateHandleStore}} has too many responsibilities. It would be
> better to move {{RetrievableStateStorageHelper}} out of it for a better
> separation of concerns
> * {{ZooKeeperSubmittedJobGraphStore}} overwrites a stored {{JobGraph}} even
> if it is locked. This should not happen since it could leave another system
> in an inconsistent state (imagine a changed {{JobGraph}} which restores from
> an old checkpoint)
> * Redundant but also somewhat inconsistent put logic in the different stores
> * Shadowing of ZooKeeper specific exceptions in {{ZooKeeperStateHandleStore}}
> which were expected to be caught in {{ZooKeeperSubmittedJobGraphStore}}
> * Getting rid of the {{SubmittedJobGraphListener}} would be helpful
> These problems made me think how reliable these components actually work.
> Since these components are very important, I propose to refactor them.
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