ch.cern.dirq

Class QueueNull

java.lang.Object

ch.cern.dirq.QueueNull

All Implemented Interfaces:

Queue, Iterable<String>

public class QueueNull
extends Object
implements Queue

QueueNull - object oriented interface to a null directory based queue.
The goal of this module is to offer a null queue system using the same API as the other directory queue implementations. The queue will behave like a black hole: added data will disappear immediately so the queue will therefore always appear empty.
This can be used for testing purposes or to discard data like one would do on Unix by redirecting output to /dev/null.
Please refer to Queue for general information about directory queues.
All the methods that add data will return an invalid element name.
All the methods that work on elements will throw an UnsupportedOperationException exception.

Author:

Lionel Cons <lionel.cons@cern.ch>, Massimo Paladin <massimo.paladin@gmail.com> Copyright (C) CERN 2012-2016

Constructor Summary

Constructors

Constructor and Description
QueueNull() Constructor for the null directory queue.

Method Summary

Modifier and Type	Method and Description
String	add(byte[] data) Add byte array data to the queue.
String	add(String data) Add String data to the queue.
String	addPath(String path) Add the given file (identified by its path) to the queue and return the corresponding element name, the file must be on the same filesystem and will be moved to the queue.
int	count() Return the number of elements in the queue.
String	get(String name) Get the given locked element as String data.
byte[]	getAsByteArray(String name) Get the given locked element as byte array data.
String	getId() Return a unique identifier for the queue.
String	getPath(String path) Get the path of the given locked element.
String	getQueuePath() Return the path of the queue.
Iterator<String>	iterator() Iterator for the null directory queue.
boolean	lock(String name) Lock an element in permissive mode.
boolean	lock(String name, boolean permissive) Lock an element.
void	purge() Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
void	purge(int maxLock) Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
void	purge(int maxLock, int maxTemp) Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
void	remove(String name) Remove a locked element from the queue.
boolean	unlock(String name) Unlock an element in non-permissive mode.
boolean	unlock(String name, boolean permissive) Unlock an element.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

QueueNull

public QueueNull()

Constructor for the null directory queue.

Method Detail

getQueuePath

public String getQueuePath()

Description copied from interface: Queue

Return the path of the queue.

Specified by:

getQueuePath in interface Queue

Returns:

queue path

getId

public String getId()

Description copied from interface: Queue

Return a unique identifier for the queue.

Specified by:

getId in interface Queue

Returns:

unique queue identifier

add

public String add(String data)

Description copied from interface: Queue

Add String data to the queue.

Specified by:

add in interface Queue

Parameters:

data - data to be added

Returns:

element name (as directory_name/file_name)

add

public String add(byte[] data)

Description copied from interface: Queue

Add byte array data to the queue.

Specified by:

add in interface Queue

Parameters:

data - data to be added

Returns:

element name (as directory_name/file_name)

addPath

public String addPath(String path)
               throws IOException

Description copied from interface: Queue

Add the given file (identified by its path) to the queue and return the corresponding element name, the file must be on the same filesystem and will be moved to the queue.

Specified by:

addPath in interface Queue

Parameters:

path - path of the file to be added

Returns:

element name (as directory_name/file_name)

Throws:

IOException - if any file operation fails

get

public String get(String name)

Description copied from interface: Queue

Get the given locked element as String data.

Specified by:

get in interface Queue

Parameters:

name - name of the element to be retrieved

Returns:

data associated with the given element

getAsByteArray

public byte[] getAsByteArray(String name)

Description copied from interface: Queue

Get the given locked element as byte array data.

Specified by:

getAsByteArray in interface Queue

Parameters:

name - name of the element to be retrieved

Returns:

data associated with the given element

getPath

public String getPath(String path)

Description copied from interface: Queue

Get the path of the given locked element.
This pathFile can be read but not removed, you must use the remove() method for this purpose.

Specified by:

getPath in interface Queue

Parameters:

path - name of the element

Returns:

path of the element

lock

public boolean lock(String name)

Description copied from interface: Queue

Lock an element in permissive mode.

Specified by:

lock in interface Queue

Parameters:

name - name of the element to be locked

Returns:

true on success, false if the element could not be locked

lock

public boolean lock(String name,
                    boolean permissive)

Description copied from interface: Queue

Lock an element.

Specified by:

lock in interface Queue

Parameters:

name - name of the element to be locked

permissive - work in permissive mode

Returns:

true on success, false if the element could not be locked

unlock

public boolean unlock(String name)

Description copied from interface: Queue

Unlock an element in non-permissive mode.

Specified by:

unlock in interface Queue

Parameters:

name - name of the element to be unlocked

Returns:

true on success, false if the element could not be unlocked

unlock

public boolean unlock(String name,
                      boolean permissive)

Description copied from interface: Queue

Unlock an element.

Specified by:

unlock in interface Queue

Parameters:

name - name of the element to be unlocked

permissive - work in permissive mode

Returns:

true on success, false if the element could not be unlocked

remove

public void remove(String name)

Description copied from interface: Queue

Remove a locked element from the queue.

Specified by:

remove in interface Queue

Parameters:

name - name of the element to be removed

count

public int count()

Description copied from interface: Queue

Return the number of elements in the queue.
Locked elements are counted but temporary elements are not.

Specified by:

count in interface Queue

Returns:

number of elements in the queue

purge

public void purge()

Description copied from interface: Queue

Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
It uses default value for maxTemp and maxLock

Specified by:

purge in interface Queue

purge

public void purge(int maxLock)

Description copied from interface: Queue

Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.

Specified by:

purge in interface Queue

Parameters:

maxLock - maximum time for a locked element (in seconds); if set to 0, locked elements will not be unlocked; if set to null, the object's default value will be used

purge

public void purge(int maxLock,
                  int maxTemp)

Description copied from interface: Queue

Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.

Specified by:

purge in interface Queue

Parameters:

maxLock - maximum time for a locked element (in seconds); if set to 0, locked elements will not be unlocked; if set to null, the object's default value will be used

maxTemp - maximum time for a temporary element (in seconds); if set to 0, temporary elements will not be removed if set to null, the object's default value will be used

iterator

public Iterator<String> iterator()

Iterator for the null directory queue.

Specified by:

iterator in interface Iterable<String>