Package org.apache.curator.framework.recipes.nodes

Class PersistentTtlNode

java.lang.Object

org.apache.curator.framework.recipes.nodes.PersistentTtlNode

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public class PersistentTtlNode
extends java.lang.Object
implements java.io.Closeable

Manages a PersistentNode that uses CreateMode.CONTAINER. Asynchronously it creates or updates a child on the persistent node that is marked with a provided TTL.

The effect of this is to have a node that can be watched, etc. The child node serves as a method of having the parent node deleted if the TTL expires. i.e. if the process that is running the PersistentTtlNode crashes and the TTL elapses, first the child node will be deleted due to the TTL expiration and then the parent node will be deleted as it's a container node with no children.

PersistentTtlNode is useful when you need to create a TTL node but don't want to keep it alive manually by periodically setting data - PersistentTtlNode does that for you. Further the keep-alive is done in a way that does not generate watch triggers on the parent node.

Field Summary

Fields

Modifier and Type	Field	Description
static java.lang.String	DEFAULT_CHILD_NODE_NAME
static int	DEFAULT_TOUCH_SCHEDULE_FACTOR

Constructor Summary

Constructors

Constructor	Description
PersistentTtlNode(org.apache.curator.framework.CuratorFramework client, java.lang.String path, long ttlMs, byte[] initData)
PersistentTtlNode(org.apache.curator.framework.CuratorFramework client, java.util.concurrent.ScheduledExecutorService executorService, java.lang.String path, long ttlMs, byte[] initData, java.lang.String childNodeName, int touchScheduleFactor)

Method Summary

Modifier and Type	Method	Description
void	close()	Call when you are done with the PersistentTtlNode.
byte[]	getData()	Return the current value of our data
void	setData(byte[] data)	Set data that node should set in ZK also writes the data to the node.
void	start()	You must call start() to initiate the persistent ttl node
boolean	waitForInitialCreate(long timeout, java.util.concurrent.TimeUnit unit)	Block until the either initial node creation initiated by start() succeeds or the timeout elapses.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_CHILD_NODE_NAME

public static final java.lang.String DEFAULT_CHILD_NODE_NAME

See Also:

Constant Field Values

DEFAULT_TOUCH_SCHEDULE_FACTOR

public static final int DEFAULT_TOUCH_SCHEDULE_FACTOR

See Also:

Constant Field Values

Constructor Detail

PersistentTtlNode

public PersistentTtlNode(org.apache.curator.framework.CuratorFramework client,
                         java.lang.String path,
                         long ttlMs,
                         byte[] initData)

Parameters:

client - the client

path - path for the parent ZNode

ttlMs - max ttl for the node in milliseconds

initData - data for the node

PersistentTtlNode

public PersistentTtlNode(org.apache.curator.framework.CuratorFramework client,
                         java.util.concurrent.ScheduledExecutorService executorService,
                         java.lang.String path,
                         long ttlMs,
                         byte[] initData,
                         java.lang.String childNodeName,
                         int touchScheduleFactor)

Parameters:

client - the client

executorService - ExecutorService to use for background thread. This service should be single threaded, otherwise you may see inconsistent results.

path - path for the parent ZNode

ttlMs - max ttl for the node in milliseconds

initData - data for the node

childNodeName - name to use for the child node of the node created at path

touchScheduleFactor - how ofter to set/create the child node as a factor of the ttlMs. i.e. the child is touched every (ttlMs / touchScheduleFactor)

Method Detail

start

public void start()

You must call start() to initiate the persistent ttl node

waitForInitialCreate

public boolean waitForInitialCreate(long timeout,
                                    java.util.concurrent.TimeUnit unit)
                             throws java.lang.InterruptedException

Block until the either initial node creation initiated by start() succeeds or the timeout elapses.

Parameters:

timeout - the maximum time to wait

unit - time unit

Returns:

if the node was created before timeout

Throws:

java.lang.InterruptedException - if the thread is interrupted

setData

public void setData(byte[] data)
             throws java.lang.Exception

Set data that node should set in ZK also writes the data to the node. NOTE: it is an error to call this method after start() but before the initial create has completed. Use waitForInitialCreate(long, TimeUnit) to ensure initial creation.

Parameters:

data - new data value

Throws:

java.lang.Exception - errors

getData

public byte[] getData()

Return the current value of our data

Returns:

our data

close

public void close()

Call when you are done with the PersistentTtlNode. Note: the ZNode is not immediately deleted. However, if no other PersistentTtlNode with the same path is running the node will get deleted based on the ttl.

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable