[jira] [Commented] (RATIS-2509) Introduce local read API to reduce serde cost

["Ivan Andika (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/RATIS-2509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18078391#comment-18078391 ] 

Ivan Andika commented on RATIS-2509:
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We can also apply this to write, but the solution might be more complex since write need to deal with mechanisms such as RetryCache, Append Logs, etc.

> Introduce local read API to reduce serde cost
> ---------------------------------------------
>
>                 Key: RATIS-2509
>                 URL: https://issues.apache.org/jira/browse/RATIS-2509
>             Project: Ratis
>          Issue Type: Improvement
>            Reporter: Ivan Andika
>            Assignee: Ivan Andika
>            Priority: Major
>         Attachments: om-benchmark-leader-read-all-ratis.html
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Recently, we did a benchmark comparing the OM leader-read that does not go through Ratis and OM leader read that go through Ratis (through submitClientRequestAsync). We saw that there is up to 25% decrease in read throughput although the we make the raft.server.read.option to be DEFAULT which should return immediately (235020 QPS -> 180433 QPS or 24% reduction in throughput for pure reads with 100 threads).
> The overheads seem to be because of request/response proto conversion, RaftClientRequest construction, future chaining, .get() blocking, Ratis metrics/reply building, and parsing the Ratis response back into OMResponse. See [^om-benchmark-leader-read-all-ratis.html] for the flamegraph.
> This means that if we submit linearizable read to follower, we incurs these overhead on top of the linearizable read overhead (e.g. ReadIndex, etc).
> We can try to find a way to reduce this overhead. We might need to implement another read flow without the overhead (unlike writes which requires AppendEntries request to the followers which require serde, read can be served locally). 
> One idea is that if we are submitting to RaftServer, we can use submitServerRequestAsync which does not require RaftClientRequest and RaftClientReply serde.



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