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https://issues.apache.org/jira/browse/RATIS-666?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16918976#comment-16918976
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Tsz Wo Nicholas Sze commented on RATIS-666:
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If the connection is good, heartbeats in both pipeline 1 and 2 will be good.
When the leader in pipeline 1 calls appendEntries, since the follower is bad,
it will fail. When the leader in pipeline 2 calls appendEntries, it will
succeed.
Suppose there is no appendEntries in pipeline 1, the leader won't realize the
follower is bad as long as all the previous calls were acknowledged.
> Coalesced heartbeat in multiraft
> --------------------------------
>
> Key: RATIS-666
> URL: https://issues.apache.org/jira/browse/RATIS-666
> Project: Ratis
> Issue Type: Improvement
> Components: raft-group
> Reporter: Li Cheng
> Priority: Major
>
> I'm using this issue to discuss the coalesced heartbeat plan in multi-raft.
> We are looking at incorporating multi-raft feature in ratis into Hadoop
> Ozone. So in ozone, every datanode would be in multiple raft groups or say
> pipelines with multi-raft, which brings:
> # Is there any plan for coalesced heartbeat on single node?
> # Are we going to use gRPC to achieve coalesced heartbeat like what
> cockroach does? Shall we assume only Java APIs are required?
> # Either we have coalesced heartbeat, every node would have chances to be
> selected as leader in each raft group. So to the extreme extend, one node,
> say node A, would be the leader to all raft groups. If we implement coalesced
> heartbeat, there would more easily push node A to be the bottleneck for
> future stumbling in performance. Any idea on how to avoid this extremity?
> Maybe do a candidate scrub?
> # How do we plan to test the 'single node, multi raft groups' scenario?
> Furthermore, if we allow coalesced heartbeat configurable, how to determine
> when and whether to use it?
>
> [~szetszwo] [~Sammi] [~xyao] [~waterlx]
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