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https://issues.apache.org/jira/browse/KAFKA-3210?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15206935#comment-15206935
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Flavio Junqueira commented on KAFKA-3210:
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[~granthenke] my main goal here is to have access to the async API and have
more control over what happens between sessions. I'm more used to programming
against zookeeper directly, so I'm more inclined to pursue that direction.
Also, given how ZkUtils is structured, it is not entirely clear to me how much
we would be able to benefit from the recipes that curator can offer. Having
said that, I don't have any major concern with using a different wrapper if
this community prefers that option as long as we are able to make use of
asynchronous calls and have more control over session creation.
> 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 new logic for
> session management, which is currently handled entirely by ZkClient. We will
> also need to implement the subscription mechanism for event notifications
> (see ZooKeeperLeaderElector as a an exemple).
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