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https://issues.apache.org/jira/browse/RATIS-2055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17836383#comment-17836383
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Duong commented on RATIS-2055:
------------------------------
cc. [~szetszwo] , [~tanxinyu]
> Changed logic of LeaderState.isReady impacts application
> --------------------------------------------------------
>
> Key: RATIS-2055
> URL: https://issues.apache.org/jira/browse/RATIS-2055
> Project: Ratis
> Issue Type: Bug
> Reporter: Duong
> Priority: Major
>
> RATIS-2019 changes the logic of `LeaderState.isReady`. Before, isReady itself
> performs the logic to check if the leader state is ready. After the change,
> the logic is moved to `LeaderState.checkReady` and `isReady` now only reads
> the result.
> This change impacts client applications that rely on `isReady` check. For
> example, Ozone's SCMStateMachine [listens to notifyTermIndexUpdated
> |https://github.com/apache/ozone/blob/5ff79613e546a09f23b2c3bae61d62fb757eaf70/hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/ha/SCMStateMachine.java#L359]
> and checks if the leader state is ready. However, because the
> `leader.checkReady` is called after the `notifyTermIndexUpdated`,
> SCMStateMachine never sees leader ready state in the intercepted
> `notifyTermIndexUpdated` events.
> {code:java|title=applyLogToStateMachine}
> CompletableFuture<Message>
> applyLogToStateMachine(ReferenceCountedObject<LogEntryProto> nextRef)
> throws RaftLogIOException {
> LogEntryProto next = nextRef.get();
> if (!next.hasStateMachineLogEntry()) {
> stateMachine.event().notifyTermIndexUpdated(next.getTerm(),
> next.getIndex());
> }
> if (next.hasConfigurationEntry()) {
> // the reply should have already been set. only need to record
> // the new conf in the metadata file and notify the StateMachine.
> state.writeRaftConfiguration(next);
> stateMachine.event().notifyConfigurationChanged(next.getTerm(),
> next.getIndex(), next.getConfigurationEntry());
> role.getLeaderState().ifPresent(leader -> leader.checkReady(next)); {code}
>
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