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https://issues.apache.org/jira/browse/KAFKA-3210?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Flavio Junqueira updated KAFKA-3210:
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Assignee: (was: Neha Narkhede)
> Using asynchronous calls through the raw ZK API in ZkUtils
> ----------------------------------------------------------
>
> Key: KAFKA-3210
> URL: https://issues.apache.org/jira/browse/KAFKA-3210
> Project: Kafka
> Issue Type: Improvement
> Components: controller, zkclient
> Affects Versions: 0.9.0.0
> Reporter: Flavio Junqueira
>
> We have observed a number of issues with the controller interaction with
> ZooKeeper mainly because ZkClient creates new sessions transparently under
> the hood. Creating sessions transparently enables, for example, old
> controller to successfully update znodes in ZooKeeper even when they aren't
> the controller any longer (e.g., KAFKA-3083). To fix this, we need to bypass
> the ZkClient lib like we did with ZKWatchedEphemeral.
> In addition to fixing such races with the controller, it would improve
> performance significantly if we used the async API (see KAFKA-3038). The
> async API is more efficient because it pipelines the requests to ZooKeeper,
> and the number of requests upon controller recovery can be large.
> This jira proposes to make these two changes to the calls in ZkUtils and to
> do it, one path is to first replace the calls in ZkUtils with raw async ZK
> calls and block so that we don't have to change the controller code in this
> phase. Once this step is accomplished and it is stable, we make changes to
> the controller to handle the asynchronous calls to ZooKeeper.
> Note that in the first step, we will need to introduce some logic for session
> management, which is currently handled entirely by ZkClient.
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