org.glassfish.grizzly.memcached.zookeeper

Class ZKClient

java.lang.Object

org.glassfish.grizzly.memcached.zookeeper.ZKClient

public class ZKClient
extends Object

Zookeeper client implementation for barrier and recoverable operation

All operations will be executed on the valid connection because the failed connection will be reconnected automatically. This has Barrier function. BarrierListener can be registered with a specific region and initial data by the registerBarrier(java.lang.String, org.glassfish.grizzly.memcached.zookeeper.BarrierListener, byte[]) method and unregistered by the unregisterBarrier(java.lang.String) method. If the zookeeper server doesn't have the data node, the given initial data will be set in the server when the registerBarrier(java.lang.String, org.glassfish.grizzly.memcached.zookeeper.BarrierListener, byte[]) method is called. If the specific data will be changed in remote zookeeper server, all clients which have joined will receive changes simultaneously. If all clients receive changes successfully, BarrierListener.onCommit(java.lang.String, java.lang.String, byte[]) will be called simultaneously at the scheduled time(data modification time + commitDelayTimeInSecs).

This also supports some safe APIs which is similar to original ZooKeeper's APIs like create, delete, exists, getChildren, getData and setData.

Examples of barrier's use: // initial <p/> final ZKClient.Builder builder = new ZKClient.Builder("myZookeeperClient", "localhost:2181"); builder.rootPath(ROOT).connectTimeoutInMillis(3000).sessionTimeoutInMillis(30000).commitDelayTimeInSecs(60); final ZKClient zkClient = builder.build(); zkClient.connect() final String registeredPath = zkClient.registerBarrier( "user", myListener, initData ); // ... // cleanup zkClient.unregisterBarrier( "user" ); zkClient.shutdown();

[NOTE] Zookeeper already guides some simple barrier examples: http://zookeeper.apache.org/doc/r3.3.4/zookeeperTutorial.html http://code.google.com/p/good-samples/source/browse/trunk/zookeeper-3.x/src/main/java/com/googlecode/goodsamples/zookeeper/barrier/Barrier.java

But, their examples have a race condision issue: https://issues.apache.org/jira/browse/ZOOKEEPER-1011

Author:

Bongjae Chang

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ZKClient.Builder Builder for ZKClient

Method Summary

Methods

Modifier and Type	Method and Description
boolean	connect() Connect this client to the zookeeper server this method will wait for Watcher.Event.KeeperState#SyncConnected from the zookeeper server.
String	create(String path, byte[] data, List<org.apache.zookeeper.data.ACL> acl, org.apache.zookeeper.CreateMode createMode)
boolean	delete(String path, int version)
org.apache.zookeeper.data.Stat	exists(String path, boolean watch)
org.apache.zookeeper.data.Stat	exists(String path, org.apache.zookeeper.Watcher watch)
List<String>	getChildren(String path, boolean watch)
List<String>	getChildren(String path, org.apache.zookeeper.Watcher watcher)
byte[]	getData(String path, boolean watch, org.apache.zookeeper.data.Stat stat)
byte[]	getData(String path, org.apache.zookeeper.Watcher watcher)
String	registerBarrier(String regionName, BarrierListener listener, byte[] initialData) Register the specific barrier
org.apache.zookeeper.data.Stat	setData(String path, byte[] data, int version)
void	shutdown() Close this client
String	toString()
void	unregisterBarrier(String regionName) Unregister the listener which was registered by registerBarrier(java.lang.String, org.glassfish.grizzly.memcached.zookeeper.BarrierListener, byte[])

Methods inherited from class java.lang.Object

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

Method Detail

connect

public boolean connect()
                throws IOException,
                       InterruptedException

Connect this client to the zookeeper server

this method will wait for Watcher.Event.KeeperState#SyncConnected from the zookeeper server.

Throws:

IOException - the io exception of internal ZooKeeper

InterruptedException - the interrupted exception of internal ZooKeeper

shutdown

public void shutdown()

Close this client

registerBarrier

public String registerBarrier(String regionName,
                     BarrierListener listener,
                     byte[] initialData)

Register the specific barrier

Parameters:

regionName - specific region name

listener - BarrierListener implementations

initialData - initial data. if the zookeeper server doesn't have any data, this will be set. "null" means NO_DATA which is byte[0].

Returns:

the registered data path of the zookeeper server

unregisterBarrier

public void unregisterBarrier(String regionName)

Unregister the listener which was registered by registerBarrier(java.lang.String, org.glassfish.grizzly.memcached.zookeeper.BarrierListener, byte[])

Parameters:

regionName - specific region name

create

public String create(String path,
            byte[] data,
            List<org.apache.zookeeper.data.ACL> acl,
            org.apache.zookeeper.CreateMode createMode)

exists

public org.apache.zookeeper.data.Stat exists(String path,
                                    boolean watch)

exists

public org.apache.zookeeper.data.Stat exists(String path,
                                    org.apache.zookeeper.Watcher watch)

getChildren

public List<String> getChildren(String path,
                       boolean watch)

getChildren

public List<String> getChildren(String path,
                       org.apache.zookeeper.Watcher watcher)

getData

public byte[] getData(String path,
             boolean watch,
             org.apache.zookeeper.data.Stat stat)

getData

public byte[] getData(String path,
             org.apache.zookeeper.Watcher watcher)

setData

public org.apache.zookeeper.data.Stat setData(String path,
                                     byte[] data,
                                     int version)

delete

public boolean delete(String path,
             int version)

toString

public String toString()

Overrides:

toString in class Object