[jira] [Updated] (ZOOKEEPER-2037) ZooKeeper methods to wait on client connection (re)establishment.

["Hongchao Deng (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-2037?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hongchao Deng updated ZOOKEEPER-2037:
-------------------------------------
    Attachment: ZOOKEEPER-2037.patch

> ZooKeeper methods to wait on client connection (re)establishment.
> -----------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2037
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2037
>             Project: ZooKeeper
>          Issue Type: Sub-task
>          Components: java client
>            Reporter: Hongchao Deng
>            Assignee: Hongchao Deng
>         Attachments: ZOOKEEPER-2037.patch
>
>
> When a ZooKeeper object is created and returned, it is not guaranteed that connection to a server is established.
> Usually, a wait/signal pattern is used for the ZK watcher
> {code}
> latch = new CountDownLatch(1)
> zk = new ZooKeeper(..., new Watcher() {
>   override void process(WatchedEvent event) {
>     if (event.type = SyncConnected) {
>       latch.countDown()
>     }
>   }
> },...)
> latch.wait();
> // connection has been established. do something with zk.
> {code}
> There are two disadvantages:
> 1. The latch object isn't being garbage-collected. Because the watcher keeps monitoring all kinds of events.
> 2. With the introduction of dynamic reconfig, client move to other servers on needed and this latch method doesn't work so well.
> Here I propose to add (both sync and async) wait methods to act as latch for connection establish such that it becomes much easier to manage and work around:
> {code}
> zk = new ZooKeeper(...)
> zk.waitUntilConnected()
> {code}



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