org.apache.hadoop.hbase.zookeeper

Class ZKNodeTracker

java.lang.Object

org.apache.hadoop.hbase.zookeeper.ZKListener

org.apache.hadoop.hbase.zookeeper.ZKNodeTracker

Direct Known Subclasses:

ClusterStatusTracker, LoadBalancerTracker, MasterAddressTracker, RegionNormalizerTracker, SnapshotCleanupTracker, SplitOrMergeTracker.SwitchStateTracker

@InterfaceAudience.Private
public abstract class ZKNodeTracker
extends ZKListener

Tracks the availability and value of a single ZooKeeper node.

Utilizes the ZKListener interface to get the necessary ZooKeeper events related to the node.

This is the base class used by trackers in both the Master and RegionServers.

Field Summary

Fields

Modifier and Type	Field and Description
protected Abortable	abortable Used to abort if a fatal error occurs
private byte[]	data Data of the node being tracked
protected static org.slf4j.Logger	LOG
protected String	node Path of node being tracked
private boolean	stopped

Fields inherited from class org.apache.hadoop.hbase.zookeeper.ZKListener

watcher

Constructor Summary

Constructors

Constructor and Description
ZKNodeTracker(ZKWatcher watcher, String node, Abortable abortable) Constructs a new ZK node tracker.

Method Summary

Modifier and Type	Method and Description
byte[]	blockUntilAvailable() Gets the data of the node, blocking until the node is available.
byte[]	blockUntilAvailable(long timeout, boolean refresh) Gets the data of the node, blocking until the node is available or the specified timeout has elapsed.
boolean	checkIfBaseNodeAvailable() Checks if the baseznode set as per the property 'zookeeper.znode.parent' exists.
byte[]	getData(boolean refresh) Gets the data of the node.
String	getNode()
void	nodeCreated(String path) Called when a new node has been created.
void	nodeDataChanged(String path) Called when an existing node has changed data.
void	nodeDeleted(String path) Called when a node has been deleted
protected void	postStart() Called after start is called.
void	start() Starts the tracking of the node in ZooKeeper.
void	stop()
String	toString()

Methods inherited from class org.apache.hadoop.hbase.zookeeper.ZKListener

getWatcher, nodeChildrenChanged

Methods inherited from class java.lang.Object

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

Field Detail

LOG

protected static final org.slf4j.Logger LOG

node

protected final String node

Path of node being tracked

data

private byte[] data

Data of the node being tracked

abortable

protected final Abortable abortable

Used to abort if a fatal error occurs

stopped

private boolean stopped

Constructor Detail

ZKNodeTracker

public ZKNodeTracker(ZKWatcher watcher,
                     String node,
                     Abortable abortable)

Constructs a new ZK node tracker.

After construction, use start() to kick off tracking.

Parameters:

watcher - reference to the ZKWatcher which also contains configuration and constants

node - path of the node being tracked

abortable - used to abort if a fatal error occurs

Method Detail

start

public void start()

Starts the tracking of the node in ZooKeeper.

Use blockUntilAvailable() to block until the node is available or getData(boolean) to get the data of the node if it is available.

postStart

protected void postStart()

Called after start is called. Sub classes could implement this method to load more data on zk.

stop

public void stop()

blockUntilAvailable

public byte[] blockUntilAvailable()
                           throws InterruptedException

Gets the data of the node, blocking until the node is available.

Returns:

data of the node

Throws:

InterruptedException - if the waiting thread is interrupted

blockUntilAvailable

public byte[] blockUntilAvailable(long timeout,
                                  boolean refresh)
                           throws InterruptedException

Gets the data of the node, blocking until the node is available or the specified timeout has elapsed.

Parameters:

timeout - maximum time to wait for the node data to be available, n milliseconds. Pass 0 for no timeout.

Returns:

data of the node

Throws:

InterruptedException - if the waiting thread is interrupted

getData

public byte[] getData(boolean refresh)

Gets the data of the node.

If the node is currently available, the most up-to-date known version of the data is returned. If the node is not currently available, null is returned.

Parameters:

refresh - whether to refresh the data by calling ZK directly.

Returns:

data of the node, null if unavailable

getNode

public String getNode()

nodeCreated

public void nodeCreated(String path)

Description copied from class: ZKListener

Called when a new node has been created.

Overrides:

nodeCreated in class ZKListener

Parameters:

path - full path of the new node

nodeDeleted

public void nodeDeleted(String path)

Description copied from class: ZKListener

Called when a node has been deleted

Overrides:

nodeDeleted in class ZKListener

Parameters:

path - full path of the deleted node

nodeDataChanged

public void nodeDataChanged(String path)

Description copied from class: ZKListener

Called when an existing node has changed data.

Overrides:

nodeDataChanged in class ZKListener

Parameters:

path - full path of the updated node

checkIfBaseNodeAvailable

public boolean checkIfBaseNodeAvailable()

Checks if the baseznode set as per the property 'zookeeper.znode.parent' exists.

Returns:

true if baseznode exists. false if doesnot exists.

toString

public String toString()

Overrides:

toString in class Object