org.apache.hadoop.hbase.master.normalizer

Class RegionNormalizerWorkQueue<E>

java.lang.Object

org.apache.hadoop.hbase.master.normalizer.RegionNormalizerWorkQueue<E>

@InterfaceAudience.Private
class RegionNormalizerWorkQueue<E>
extends Object

A specialized collection that holds pending work for the RegionNormalizerWorker. It is an ordered collection class that has the following properties:

• Guarantees uniqueness of elements, as a Set.
• Consumers retrieve objects from the head, as a Queue, via take().
• Work is retrieved on a FIFO policy.
• Work retrieval blocks the calling thread until new work is available, as a BlockingQueue.
• Allows a producer to insert an item at the head of the queue, if desired.

Assumes low-frequency and low-parallelism concurrent access, so protects state using a simplistic synchronization strategy.

Field Summary

Fields

Modifier and Type	Field and Description
private LinkedHashSet<E>	delegate Underlying storage structure that gives us the Set behavior and FIFO retrieval policy.
private Condition	notEmpty Wait queue for waiting takes
private ReentrantLock	putLock Lock held by put, offer, etc
private ReentrantLock	takeLock Lock held by take, poll, etc

Constructor Summary

Constructors

Constructor and Description
RegionNormalizerWorkQueue()

Method Summary

Modifier and Type	Method and Description
void	clear() Atomically removes all of the elements from this queue.
private void	fullyLock() Locks to prevent both puts and takes.
private void	fullyUnlock() Unlocks to allow both puts and takes.
void	put(E e) Inserts the specified element at the tail of the queue, if it's not already present.
void	putAll(Collection<? extends E> c) Inserts the specified elements at the tail of the queue.
void	putAllFirst(Collection<? extends E> c) Inserts the specified elements at the head of the queue.
void	putFirst(E e) Inserts the specified element at the head of the queue.
private void	signalNotEmpty() Signals a waiting take.
int	size() Returns the number of elements in this queue.
E	take() Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

delegate

private LinkedHashSet<E> delegate

Underlying storage structure that gives us the Set behavior and FIFO retrieval policy.

takeLock

private final ReentrantLock takeLock

Lock held by take, poll, etc

notEmpty

private final Condition notEmpty

Wait queue for waiting takes

putLock

private final ReentrantLock putLock

Lock held by put, offer, etc

Constructor Detail

RegionNormalizerWorkQueue

RegionNormalizerWorkQueue()

Method Detail

signalNotEmpty

private void signalNotEmpty()

Signals a waiting take. Called only from put/offer (which do not otherwise ordinarily lock takeLock.)

fullyLock

private void fullyLock()

Locks to prevent both puts and takes.

fullyUnlock

private void fullyUnlock()

Unlocks to allow both puts and takes.

put

public void put(E e)

Inserts the specified element at the tail of the queue, if it's not already present.

Parameters:

e - the element to add

putFirst

public void putFirst(E e)

Inserts the specified element at the head of the queue.

Parameters:

e - the element to add

putAll

public void putAll(Collection<? extends E> c)

Inserts the specified elements at the tail of the queue. Any elements already present in the queue are ignored.

Parameters:

c - the elements to add

putAllFirst

public void putAllFirst(Collection<? extends E> c)

Inserts the specified elements at the head of the queue.

Parameters:

c - the elements to add

take

public E take()
       throws InterruptedException

Retrieves and removes the head of this queue, waiting if necessary until an element becomes available.

Returns:

the head of this queue

Throws:

InterruptedException - if interrupted while waiting

clear

public void clear()

Atomically removes all of the elements from this queue. The queue will be empty after this call returns.

size

public int size()

Returns the number of elements in this queue.

Returns:

the number of elements in this queue

toString

public String toString()

Overrides:

toString in class Object