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From "Neha Narkhede (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-813) Minor cleanup in Controller
Date Wed, 20 Mar 2013 15:21:15 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-813?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13607705#comment-13607705
] 

Neha Narkhede commented on KAFKA-813:
-------------------------------------

Thanks for patch v2 -

1. KafkaController
1.1 The change to OfflinePartitionsCount looks good. However, there is a distinction between
a partition whose leader is not alive but other replicas are so leader election will happen
and a partition for which all replicas are dead. In the latter case, there can be no leader
for that partition which is a much more dangerous state for a partition to be in. I suggest
two metrics, OfflinePartitionsCount to indicate the former and UnavailablePartitionsCount
to indicate the latter
1.2 I wonder why ActiveControllerCount and OfflinePartitionsCount are not part of ControllerStats
?

2. NoOpLeaderSelector
Minor code style suggestion - return is not required here.

3. PartitionStateMachine
We don't have to define the noOpLeaderSelector in the controller since it is used only in
PartitionStateMachine.handleStateChanges(). Let's move it there. The reason offlineLeaderSelector
is there since both the controller and the partition state machine access it.

Nit pick - Can we change PartitionNoReplicaOnlineException to NoReplicaForPartitionException
? :)
                
> Minor cleanup in Controller
> ---------------------------
>
>                 Key: KAFKA-813
>                 URL: https://issues.apache.org/jira/browse/KAFKA-813
>             Project: Kafka
>          Issue Type: Bug
>    Affects Versions: 0.8
>            Reporter: Swapnil Ghike
>            Assignee: Swapnil Ghike
>            Priority: Blocker
>              Labels: kafka-0.8
>             Fix For: 0.8
>
>         Attachments: kafka-813-v1.patch, kafka-813-v2.patch
>
>
> Before starting work on delete topic support, uploading a patch first to address some
minor hiccups that touch a bunch of files:
> 1. Change PartitionOfflineException to PartitionUnavailableException because in the partition
state machine we mark a partition offline when its leader is down, whereas the PartitionOfflineException
is thrown when all the assigned replicas of the partition are down.
> 2. Change PartitionOfflineRate to UnavailablePartitionRate
> 3. Remove default leader selector from partition state machine's handleStateChange. We
can specify null as default when we don't need to use a leader selector.
> 4. Include controller info in the client id of LeaderAndIsrRequest.
> 5. Rename controllerContext.allleaders to something more meaningful - partitionLeadershipInfo.
> 6. We don't need to put partition in OnlinePartition state in partition state machine
initializeLeaderAndIsrForPartition, the state change occurs in handleStateChange.
> 7. Add todo in handleStateChanges
> 8. Left a comment above ReassignedPartitionLeaderSelector that reassigned replicas are
already in the ISR (this is not true for other leader selectors), renamed the vals in the
selector.

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