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https://issues.apache.org/jira/browse/HDDS-12864?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Uma Maheswara Rao G reassigned HDDS-12864:
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Assignee: Sergey Soldatov (was: Swaminathan Balachandran)
> All commit semantics in replication writes
> -------------------------------------------
>
> Key: HDDS-12864
> URL: https://issues.apache.org/jira/browse/HDDS-12864
> Project: Apache Ozone
> Issue Type: New Feature
> Components: Ozone Client, Ozone Datanode
> Reporter: Uma Maheswara Rao G
> Assignee: Sergey Soldatov
> Priority: Major
>
> In Ozone replication(Raft based) has the semantics of majority commit. While
> this has the advantage of not suffering from a slow node, this will allow the
> system to move forward with majority replication for a short duration of time
> without having to have all 3 replicas consistently committed. Catching a slow
> replica is dependent on a raft.
> Since Ozone has a variable length of blocks, it is just fine to close the
> container/block when some of the replicas are not acknowledged in time. So,
> it does need to recopy the content to new nodes, instead, it can just move
> forward with a new pipeline.
> With this advantage, we should provide all commit semantics to make sure all
> replicas are consistently committed to a length that the client got
> acknowledgments for.
> There are two/three areas where we do the majority of commits today:
> 1. Client falls back to the majority commits in watchForCommit if all commits
> fail.
> 2. Leader DN always waits for the majority quorum for transactions
> 3. The leader only waits for self applyTransaction completion.
> Making the above scenarios streamlines and achieving all commits can bring
> all replicas into a consistent state at any point in time, on write acks.
> As a side note: Today, in EC, we already do ALL COMMIT like protocol in write
> path. Which avoids QUASI_CLOSED state altogether as replicas always have at
> the minimum length of data, as it is acknowledged to the clients.
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