[jira] [Updated] (RATIS-1548) use stateMachine#lastAppliedIndex instead of stateMachinUpdater#lastAppliedIndex when checking snapshot should be taken

["Jie Yao (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/RATIS-1548?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jie Yao updated RATIS-1548:
---------------------------
    Summary: use stateMachine#lastAppliedIndex instead of stateMachinUpdater#lastAppliedIndex when checking snapshot should be taken  (was: use stateMachine#lastAppliedIndex instead of stateMachinUpdater#lastAppliedIndex when check snapshot should be taken)

> use stateMachine#lastAppliedIndex instead of stateMachinUpdater#lastAppliedIndex when checking snapshot should be taken
> -----------------------------------------------------------------------------------------------------------------------
>
>                 Key: RATIS-1548
>                 URL: https://issues.apache.org/jira/browse/RATIS-1548
>             Project: Ratis
>          Issue Type: Bug
>            Reporter: Jie Yao
>            Assignee: Jie Yao
>            Priority: Major
>
> for now, the following is used to check whether a snapshot should be taken
> {code:java}
> return state == State.RUNNING && getLastAppliedIndex() - snapshotIndex.get() >= autoSnapshotThreshold; {code}
> but `getLastAppliedIndex` is the index recorded by stateMachineUpdater, not state machine itself. in some other case (for example, om), the lastAppliedIndex of state machine will not be updated immediately after `applyTransaction` is called . in om , lastAppliedIndex will be updated until the ready queue of double buffer is flushed.
> so here `stateMachineUpdater#getLastAppliedIndex()` does not always equal to `stateMachine#lastAppliedIndex`



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