When you have many workers (threads/servers) giving service, and a cached item expensive to produce expires, you may get several workers doing the job at the same time. More...

Inheritance diagram for PoolCounter:

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List of all members.

Public Member Functions
	acquireForAnyone ()
	I want to do this task, but if anyone else does it instead, it's also fine for me.
	acquireForMe ()
	I want to do this task and I need to do it myself.
	release ()
	I have successfully finished my task.
Static Public Member Functions
static	factory ($type, $key)
	Create a Pool counter.
Public Attributes
	$maxqueue
	$timeout
	$workers
const	DONE = 3
const	ERROR = -1
const	LOCK_HELD = -5
const	LOCKED = 1
const	NOT_LOCKED = -2
const	QUEUE_FULL = -3
const	RELEASED = 2
const	TIMEOUT = -4
Protected Member Functions
	__construct ($conf, $type, $key)
Protected Attributes
	$key
	$key: All workers with the same key share the lock.

Detailed Description

When you have many workers (threads/servers) giving service, and a cached item expensive to produce expires, you may get several workers doing the job at the same time.

Given enough requests and the item expiring fast (non-cacheable, lots of edits...) that single work can end up unfairly using most (all) of the cpu of the pool. This is also known as 'Michael Jackson effect' since this effect triggered on the english wikipedia on the day Michael Jackson died, the biographical article got hit with several edits per minutes and hundreds of read hits.

The PoolCounter provides semaphore semantics for restricting the number of workers that may be concurrently performing such single task.

By default PoolCounter_Stub is used, which provides no locking. You can get a useful one in the PoolCounter extension.

Definition at line 21 of file PoolCounter.php.

Constructor & Destructor Documentation

PoolCounter::__construct	(	$	conf,
		$	type,
		$	key
	)		`[protected]`

Definition at line 87 of file PoolCounter.php.

References $key.

Member Function Documentation

PoolCounter::acquireForAnyone ( ) [abstract]

I want to do this task, but if anyone else does it instead, it's also fine for me.

I will read its cached data.

Returns:: Locked/Done/Error

Reimplemented in PoolCounter_Stub.

PoolCounter::acquireForMe ( ) [abstract]

I want to do this task and I need to do it myself.

Returns:: Locked/Error

Reimplemented in PoolCounter_Stub.

static PoolCounter::factory	(	$	type,
		$	key
	)		`[static]`

Create a Pool counter.

This should only be called from the PoolWorks.

Parameters:

$type
$key

Returns:: PoolCounter

Definition at line 76 of file PoolCounter.php.

References $key, and $wgPoolCounterConf.

Referenced by PoolCounterWork\__construct().

Here is the caller graph for this function:

PoolCounter::release ( ) [abstract]

I have successfully finished my task.

Lets another one grab the lock, and returns the workers waiting on acquireForAnyone()

Returns:: Released/NotLocked/Error

Reimplemented in PoolCounter_Stub.

Member Data Documentation

PoolCounter::$key [protected]

$key: All workers with the same key share the lock.

$workers: It wouldn't be a good idea to have more than this number of workers doing the task simultaneously. $maxqueue: If this number of workers are already working/waiting, fail instead of wait. $timeout: Maximum time in seconds to wait for the lock.

Definition at line 66 of file PoolCounter.php.

Referenced by __construct(), and factory().

PoolCounter::$maxqueue

Definition at line 66 of file PoolCounter.php.

PoolCounter::$timeout

Definition at line 66 of file PoolCounter.php.

PoolCounter::$workers

Definition at line 66 of file PoolCounter.php.

const PoolCounter::DONE = 3

Definition at line 26 of file PoolCounter.php.

Referenced by PoolCounterWork\execute().

const PoolCounter::ERROR = -1