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From "Ismael Juma (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-5879) Controller should read the latest IsrChangeNotification znodes when handling IsrChangeNotification event
Date Thu, 28 Sep 2017 11:01:00 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-5879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16183999#comment-16183999
] 

Ismael Juma commented on KAFKA-5879:
------------------------------------

Discussion in progress on whether we need this for 1.0.0 or not.

> Controller should read the latest IsrChangeNotification znodes when handling IsrChangeNotification
event
> --------------------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-5879
>                 URL: https://issues.apache.org/jira/browse/KAFKA-5879
>             Project: Kafka
>          Issue Type: Bug
>            Reporter: Dong Lin
>            Assignee: Dong Lin
>            Priority: Critical
>             Fix For: 1.0.0
>
>
> Currently controller can be very inefficient in handling IsrChangeNotification event
because it may need to access znode O(n^2) times to handle O( n ) IsrChangeNotification znodes.
> For example, say there are 100 IsrChangeNotification nodes added to the zookeeper. This
will generate 100 IsrChangeNotification events with children [1], [1, 2], [1, 2, 3], ... [1,
2, .. 100]. Let's say the controller now needs to handle the IsrChangeNotification event with
children [1, 2, ... 100]. Controller will read zookeeper 100 times, delete these 100 znodes,
which further generates 100 IsrChangeNotification events with children count from 0 to 99.
> The main cause of the problem is that, controller will attempt to access zookeeper n
times, where n is the count of the children at the time the IsrChangeNotification event is
generated, even though there is no IsrChangeNotification znodes in the zookeeper.



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