at.salzburgresearch.nodekeeper

Class NodeKeeper

java.lang.Object

at.salzburgresearch.nodekeeper.NodeKeeper

All Implemented Interfaces:

org.apache.zookeeper.Watcher

public class NodeKeeper
extends Object
implements org.apache.zookeeper.Watcher

NodeKeeper is a ZooKeeper API wrapper, that makes it more comfortable to work with ZooKeeper nodes. The main methods are:

• handle reading and writing nodes with type specific (and expandable) data handlers
• handle node lifecycle easily (no existence checks etc.)
• appending NodeListeners to path patterns

Author: Thomas Kurz (tkurz@apache.org)

Nested Class Summary

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

org.apache.zookeeper.Watcher.Event

Constructor Summary

Constructors

Constructor and Description
NodeKeeper(String connectionString, int sessionTimeout, Properties properties) NodeKeeper enables a ZooKeeper connection.
NodeKeeper(String connectionString, int sessionTimeout, Properties properties, String startNode) NodeKeeper enables a ZooKeeper connection.

Method Summary

Methods

Modifier and Type	Method and Description
void	addDataHandler(DataHandler dataHandler) Adds a data handler that is used to read and write node data
void	addListener(String pathPattern, NodeListener listener) Appends a listener to the pathPattern.
<T> void	deleteNode(Node<T> node) delete the node from ZooKeeper
DataHandler	getDataHandler(Class clazz)
org.apache.zookeeper.ZooKeeper	getZooKeeper() returns the ZooKeeper connection if it is connected
boolean	hasChildren(String path)
<T> Set<Node<T>>	listChildrenNodes(String path, Class<T> clazz)
List<DataHandler>	listDataHandlers()
int	nbOfChildren(String path)
void	process(org.apache.zookeeper.WatchedEvent watchedEvent)
<T> Node<T>	readNode(String path, Class<T> clazz) read node to ZooKeeper, return null if it does not exist
void	removeListener(String pathPattern, NodeListener listener)
void	shutdown() shut down ZooKeeper connection
void	startListeners()
<T> void	writeNode(Node<T> node, Class<T> clazz) write node to ZooKeeper, create parent nodes recursively if they do not exist

Methods inherited from class java.lang.Object

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

Constructor Detail

NodeKeeper

public NodeKeeper(String connectionString,
          int sessionTimeout,
          Properties properties)
           throws InterruptedException,
                  NodeKeeperException,
                  IOException

NodeKeeper enables a ZooKeeper connection.

Parameters:

connectionString - comma-separated list of url-strings of ZooKeeper servers

sessionTimeout - sessionTimeout for connection

properties - should be persisted at the end to guarantee clean node versioning (on re-startup)

Throws:

IOException

InterruptedException

NodeKeeperException

NodeKeeper

public NodeKeeper(String connectionString,
          int sessionTimeout,
          Properties properties,
          String startNode)
           throws InterruptedException,
                  IOException,
                  NodeKeeperException

NodeKeeper enables a ZooKeeper connection.

Parameters:

connectionString - comma-separated list of url-strings of ZooKeeper servers

sessionTimeout - sessionTimeout for connection

properties - should be persisted at the end to guarantee clean node versioning (on re-startup)

startNode - juts children of this node and the node itself are taken into account

Throws:

IOException

InterruptedException

NodeKeeperException

Method Detail

startListeners

public void startListeners()
                    throws InterruptedException,
                           NodeKeeperException,
                           IOException

Throws:

InterruptedException

NodeKeeperException

IOException

process

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

Specified by:

process in interface org.apache.zookeeper.Watcher

getZooKeeper

public org.apache.zookeeper.ZooKeeper getZooKeeper()

returns the ZooKeeper connection if it is connected

Returns:

shutdown

public void shutdown()
              throws InterruptedException

shut down ZooKeeper connection

Throws:

InterruptedException

readNode

public <T> Node<T> readNode(String path,
                   Class<T> clazz)
                 throws InterruptedException,
                        NodeKeeperException,
                        IOException

read node to ZooKeeper, return null if it does not exist

Type Parameters:

T - class of the node, is handled by handler

Parameters:

path - path of the node

clazz - class of the node, is handled by handler

Returns:

Throws:

InterruptedException

NodeKeeperException

IOException

writeNode

public <T> void writeNode(Node<T> node,
                 Class<T> clazz)
               throws InterruptedException,
                      NodeKeeperException,
                      IOException

write node to ZooKeeper, create parent nodes recursively if they do not exist

Type Parameters:

T - the handler for writing the data

Parameters:

node - the node that should be written

clazz -

Throws:

InterruptedException

NodeKeeperException

IOException

deleteNode

public <T> void deleteNode(Node<T> node)
                throws InterruptedException,
                       NodeKeeperException

delete the node from ZooKeeper

Type Parameters:

T - the class for the handler (not used in this method)

Parameters:

node - a node instance

Throws:

InterruptedException

NodeKeeperException

listChildrenNodes

public <T> Set<Node<T>> listChildrenNodes(String path,
                                 Class<T> clazz)
                               throws InterruptedException,
                                      NodeKeeperException

Throws:

InterruptedException

NodeKeeperException

nbOfChildren

public int nbOfChildren(String path)
                 throws NodeKeeperException,
                        InterruptedException

Throws:

NodeKeeperException

InterruptedException

hasChildren

public boolean hasChildren(String path)
                    throws NodeKeeperException,
                           InterruptedException

Throws:

NodeKeeperException

InterruptedException

addListener

public void addListener(String pathPattern,
               NodeListener listener)
                 throws NodeKeeperException

Appends a listener to the pathPattern. The methods of the lister are called when a node that matches the pathPattern is created, updated or deleted.

Parameters:

pathPattern - a regular expression that declares the node the listener is listen to.

listener - a implementation of the NodeListener interface that handles the node events create, update and delete.

Throws:

NodeKeeperException

removeListener

public void removeListener(String pathPattern,
                  NodeListener listener)

addDataHandler

public void addDataHandler(DataHandler dataHandler)

Adds a data handler that is used to read and write node data

Parameters:

dataHandler -

getDataHandler

public DataHandler getDataHandler(Class clazz)

listDataHandlers

public List<DataHandler> listDataHandlers()