Package org.apache.curator.framework.recipes.queue

Class QueueBuilder<T>

java.lang.Object

org.apache.curator.framework.recipes.queue.QueueBuilder<T>

public class QueueBuilder<T>
extends java.lang.Object

The builder for both DistributedQueue and DistributedPriorityQueue

Method Summary

Modifier and Type	Method	Description
DistributedDelayQueue<T>	buildDelayQueue()	Build a DistributedDelayQueue from the current builder values.
static <T> QueueBuilder<T>	builder(org.apache.curator.framework.CuratorFramework client, QueueConsumer<T> consumer, QueueSerializer<T> serializer, java.lang.String queuePath)	Allocate a new builder
DistributedIdQueue<T>	buildIdQueue()	Build a DistributedIdQueue from the current builder values
DistributedPriorityQueue<T>	buildPriorityQueue(int minItemsBeforeRefresh)	Build a DistributedPriorityQueue from the current builder values.
DistributedQueue<T>	buildQueue()	Build a DistributedQueue from the current builder values
QueueBuilder<T>	executor(java.util.concurrent.Executor executor)	Change the executor used.
QueueBuilder<T>	finalFlushTime(int time, java.util.concurrent.TimeUnit unit)	Sets an amount of time to call DistributedQueue.flushPuts(long, TimeUnit) when the queue is closed.
QueueBuilder<T>	lockPath(java.lang.String path)	Without a lock set, queue items are removed before being sent to the queue consumer.
QueueBuilder<T>	maxItems(int maxItems)	By default, the various queues are unbounded.
QueueBuilder<T>	putInBackground(boolean putInBackground)	By default, messages are added in the background.
QueueBuilder<T>	threadFactory(java.util.concurrent.ThreadFactory factory)	Change the thread factory used.

Methods inherited from class java.lang.Object

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

Method Detail

builder

public static <T> QueueBuilder<T> builder(org.apache.curator.framework.CuratorFramework client,
                                          QueueConsumer<T> consumer,
                                          QueueSerializer<T> serializer,
                                          java.lang.String queuePath)

Allocate a new builder

Parameters:

client - the curator client

consumer - functor to consume messages - NOTE: pass null to make this a producer-only queue

serializer - serializer to use for items

queuePath - path to store queue

Returns:

builder

buildQueue

public DistributedQueue<T> buildQueue()

Build a DistributedQueue from the current builder values

Returns:

distributed queue

buildIdQueue

public DistributedIdQueue<T> buildIdQueue()

Build a DistributedIdQueue from the current builder values

Returns:

distributed id queue

buildPriorityQueue

public DistributedPriorityQueue<T> buildPriorityQueue(int minItemsBeforeRefresh)

Build a DistributedPriorityQueue from the current builder values.

When the priority queue detects an item addition/removal, it will stop processing its current list of items and refresh the list. minItemsBeforeRefresh modifies this. It determines the minimum number of items from the active list that will get processed before a refresh.

Due to a quirk in the way ZooKeeper notifies changes, the queue will get an item addition/remove notification after every item is processed. This can lead to poor performance. Set minItemsBeforeRefresh to the value your application can tolerate being out of sync.

For example: if the queue sees 10 items to process, it will end up making 10 calls to ZooKeeper to check status. You can control this by setting minItemsBeforeRefresh to 10 (or more) and the queue will only refresh with ZooKeeper after 10 items are processed

Parameters:

minItemsBeforeRefresh - minimum items to process before refreshing the item list

Returns:

distributed priority queue

buildDelayQueue

public DistributedDelayQueue<T> buildDelayQueue()

Build a DistributedDelayQueue from the current builder values.

Returns:

distributed delay queue

threadFactory

public QueueBuilder<T> threadFactory(java.util.concurrent.ThreadFactory factory)

Change the thread factory used. The default is Executors.defaultThreadFactory()

Parameters:

factory - new thread factory to use

Returns:

this

executor

public QueueBuilder<T> executor(java.util.concurrent.Executor executor)

Change the executor used. The default is MoreExecutors#directExectutor()

Parameters:

executor - new executor to use

Returns:

this

lockPath

public QueueBuilder<T> lockPath(java.lang.String path)

Without a lock set, queue items are removed before being sent to the queue consumer. This can result in message loss if the consumer fails to complete the message or the process dies.

Use a lock to make the message recoverable. A lock is held while the message is being processed - this prevents other processes from taking the message. The message will not be removed from the queue until the consumer functor returns. Thus, if there is a failure or the process dies, the message will get sent to another process. There is a small performance penalty for this behavior however.

Parameters:

path - path for the lock

Returns:

this

maxItems

public QueueBuilder<T> maxItems(int maxItems)

By default, the various queues are unbounded. This method allows setting a max number of items to have in the queue. With this value set, the various put methods will block when the number of items in the queue approaches maxItems. NOTE: maxItems cannot be exactly achieved. The only guarantee is that approximately maxItems will cause puts to block.

Parameters:

maxItems - the upper bound for the queue

Returns:

this

putInBackground

public QueueBuilder<T> putInBackground(boolean putInBackground)

By default, messages are added in the background. However, this can flood the background thread.

Parameters:

putInBackground - true to put in the background (default). false to put in the foreground.

Returns:

this

finalFlushTime

public QueueBuilder<T> finalFlushTime(int time,
                                      java.util.concurrent.TimeUnit unit)

Sets an amount of time to call DistributedQueue.flushPuts(long, TimeUnit) when the queue is closed. The default is 5 seconds. Pass 0 to turn flushing on close off.

Parameters:

time - time

unit - the unit

Returns:

this