Hongchao Deng created ZOOKEEPER-2037:
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Summary: 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
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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