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From "nkeywal (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5573) Replace client ZooKeeper watchers by simple ZooKeeper reads
Date Wed, 21 Mar 2012 15:19:39 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13234413#comment-13234413
] 

nkeywal commented on HBASE-5573:
--------------------------------

bq; This seems way broke Nicolas: "zk.ZooKeeper contains (hb.ZooKeeperWatcher implements zk.ZooKeeper)"
I wanted to say that in ZK API, you want give a Watcher as a parameter to the ZooKeeper object.
In HBase, this watcher is the ZooKeeperWatcher. And this ZooKeeperWatcher  contains the RecoverableZK
that contains the ZooKeeper object, so we have a loop.

bq. Is ZKW doing everything, not just Watching? If so, would fixing this help?
Yes it does everything. With the split there is now a new object when we just want to read/write.

For the name, let's go for NoWatchZK.

I'm currently testing the patch. There is still an issue with stuff like ZKAssign.getData:
it sets a watcher, but is it really needed?

                
> Replace client ZooKeeper watchers by simple ZooKeeper reads
> -----------------------------------------------------------
>
>                 Key: HBASE-5573
>                 URL: https://issues.apache.org/jira/browse/HBASE-5573
>             Project: HBase
>          Issue Type: Improvement
>          Components: client, zookeeper
>    Affects Versions: 0.96.0
>            Reporter: nkeywal
>            Assignee: nkeywal
>            Priority: Minor
>         Attachments: 5573.v1.patch, 5573.v2.patch
>
>
> Some code in the package needs to read data in ZK. This could be done by a simple read,
but is actually implemented with a watcher. This holds ZK resources.
> Fixing this could also be an opportunity to remove the need for the client to provide
the master address and port.

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