org.apache.hadoop.hbase.zookeeper

Class PendingWatcher

java.lang.Object

org.apache.hadoop.hbase.zookeeper.PendingWatcher

All Implemented Interfaces:

org.apache.zookeeper.Watcher

class PendingWatcher
extends Object
implements org.apache.zookeeper.Watcher

Placeholder of a watcher which might be triggered before the instance is not yet created.

ZooKeeper starts its event thread within its constructor (and that is an anti-pattern), and the watcher passed to the constructor might be called back by the event thread before you get the instance of ZooKeeper from the constructor. If your watcher calls methods of ZooKeeper, pass this placeholder to the constructor of the ZooKeeper, create your watcher using the instance of ZooKeeper, and then call the method PendingWatcher.prepare.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.zookeeper.Watcher

org.apache.zookeeper.Watcher.Event, org.apache.zookeeper.Watcher.WatcherType

Field Summary

Fields

Modifier and Type	Field and Description
private InstancePending<org.apache.zookeeper.Watcher>	pending

Constructor Summary

Constructors

Constructor and Description
PendingWatcher()

Method Summary

Modifier and Type	Method and Description
(package private) void	prepare(org.apache.zookeeper.Watcher watcher) Associates the substantial watcher of processing events.
void	process(org.apache.zookeeper.WatchedEvent event)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

pending

private final InstancePending<org.apache.zookeeper.Watcher> pending

Constructor Detail

PendingWatcher

PendingWatcher()

Method Detail

process

public void process(org.apache.zookeeper.WatchedEvent event)

Specified by:

process in interface org.apache.zookeeper.Watcher

prepare

void prepare(org.apache.zookeeper.Watcher watcher)

Associates the substantial watcher of processing events. This method should be called once, and watcher should be non-null. This method is expected to call as soon as possible because the event processing, being invoked by the ZooKeeper event thread, is uninterruptibly blocked until this method is called.