[jira] [Commented] (KAFKA-5258) move all partition and replica state transition rules into their states

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-5258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16015555#comment-16015555 ] 

ASF GitHub Bot commented on KAFKA-5258:
---------------------------------------

Github user asfgit closed the pull request at:

    https://github.com/apache/kafka/pull/3071


> move all partition and replica state transition rules into their states
> -----------------------------------------------------------------------
>
>                 Key: KAFKA-5258
>                 URL: https://issues.apache.org/jira/browse/KAFKA-5258
>             Project: Kafka
>          Issue Type: Sub-task
>            Reporter: Onur Karaman
>            Assignee: Onur Karaman
>            Priority: Minor
>             Fix For: 0.11.0.0
>
>
> Today the PartitionStateMachine and ReplicaStateMachine defines and asserts the valid state transitions inline for each state, looking something like:
> {code}
> private def handleStateChange(...) {
>   targetState match {
>     case stateA => {
>       assertValidPreviousStates(topicAndPartition, List(stateX, stateY, stateZ), stateA)
>       // actual work
>     }
>     case stateB => {
>       assertValidPreviousStates(topicAndPartition, List(stateD, stateE), stateB)
>       // actual work
>     }
>   }
> }
> {code}
> It would be cleaner to move all partition and replica state transition rules into their states and simply do the assertion at the top of the handleStateChange method like so:
> {code}
> private def handleStateChange(...) {
>   assertValidTransition(targetState)
>   targetState match {
>     case stateA => {
>       // actual work
>     }
>     case stateB => {
>       // actual work
>     }
>   }
> }
> sealed trait State {
>   def state: Byte
>   def validPreviousStates: Set[State]
> }
> case object StateA extends State {
>   val state: Byte = 1
>   val validPreviousStates: Set[State] = Set(StateX)
> }
> case object StateB extends State {
>   val state: Byte = 2
>   val validPreviousStates: Set[State] = Set(StateX, StateY, StateZ)
> }
> {code}



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