Dong Lin created KAFKA-5879:
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Summary: 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
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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