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Merge "Added reentrant lock support to BagOStuff"

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jenkins-bot 2015-08-25 01:28:24 +00:00 committed by Gerrit Code Review
commit f0c88b2163
5 changed files with 71 additions and 36 deletions
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86
includes/libs/objectcache/BagOStuff.php
View file

@ -43,16 +43,17 @@ use Psr\Log\NullLogger;
* @ingroup Cache
*/
abstract class BagOStuff implements LoggerAwareInterface {
private $debugMode = false;
/** @var array[] Lock tracking */
protected $locks = array();
/** @var integer */
protected $lastError = self::ERR_NONE;
/**
* @var LoggerInterface
*/
/** @var LoggerInterface */
protected $logger;
/** @var bool */
private $debugMode = false;
/** Possible values for getLastError() */
const ERR_NONE = 0; // no error
const ERR_NO_RESPONSE = 1; // no response
@ -221,49 +222,77 @@ abstract class BagOStuff implements LoggerAwareInterface {
}
/**
* Acquire an advisory lock on a key string
*
* Note that if reentry is enabled, duplicate calls ignore $expiry
*
* @param string $key
* @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
* @param int $expiry Lock expiry [optional]; 1 day maximum
* @param string $rclass Allow reentry if set and the current lock used this value
* @return bool Success
*/
public function lock( $key, $timeout = 6, $expiry = 6 ) {
public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
// Avoid deadlocks and allow lock reentry if specified
if ( isset( $this->locks[$key] ) ) {
if ( $rclass != '' && $this->locks[$key]['class'] === $rclass ) {
++$this->locks[$key]['depth'];
return true;
} else {
return false;
}
}
$expiry = min( $expiry ?: INF, 86400 );
$this->clearLastError();
$timestamp = microtime( true ); // starting UNIX timestamp
if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
return true;
$locked = true;
} elseif ( $this->getLastError() || $timeout <= 0 ) {
return false; // network partition or non-blocking
$locked = false; // network partition or non-blocking
} else {
$uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us)
$sleep = 2 * $uRTT; // rough time to do get()+set()
$attempts = 0; // failed attempts
do {
if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
// Exponentially back off after failed attempts to avoid network spam.
// About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
$sleep *= 2;
}
usleep( $sleep ); // back off
$this->clearLastError();
$locked = $this->add( "{$key}:lock", 1, $expiry );
if ( $this->getLastError() ) {
$locked = false; // network partition
break;
}
} while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
}
$uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us)
$sleep = 2 * $uRTT; // rough time to do get()+set()
$attempts = 0; // failed attempts
do {
if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
// Exponentially back off after failed attempts to avoid network spam.
// About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
$sleep *= 2;
}
usleep( $sleep ); // back off
$this->clearLastError();
$locked = $this->add( "{$key}:lock", 1, $expiry );
if ( $this->getLastError() ) {
return false; // network partition
}
} while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
if ( $locked ) {
$this->locks[$key] = array( 'class' => $rclass, 'depth' => 1 );
}
return $locked;
}
/**
* Release an advisory lock on a key string
*
* @param string $key
* @return bool Success
*/
public function unlock( $key ) {
return $this->delete( "{$key}:lock" );
if ( isset( $this->locks[$key] ) && --$this->locks[$key]['depth'] <= 0 ) {
unset( $this->locks[$key] );
return $this->delete( "{$key}:lock" );
}
return true;
}
/**
@ -278,13 +307,14 @@ abstract class BagOStuff implements LoggerAwareInterface {
* @param string $key
* @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
* @param int $expiry Lock expiry [optional]; 1 day maximum
* @param string $rclass Allow reentry if set and the current lock used this value
* @return ScopedCallback|null Returns null on failure
* @since 1.26
*/
final public function getScopedLock( $key, $timeout = 6, $expiry = 30 ) {
final public function getScopedLock( $key, $timeout = 6, $expiry = 30, $rclass = '' ) {
$expiry = min( $expiry ?: INF, 86400 );
if ( !$this->lock( $key, $timeout, $expiry ) ) {
if ( !$this->lock( $key, $timeout, $expiry, $rclass ) ) {
return null;
}

4
includes/libs/objectcache/HashBagOStuff.php
View file

@ -68,10 +68,6 @@ class HashBagOStuff extends BagOStuff {
}
function delete( $key ) {
if ( !isset( $this->bag[$key] ) ) {
return false;
}
unset( $this->bag[$key] );
return true;

4
includes/libs/objectcache/ReplicatedBagOStuff.php
View file

@ -104,8 +104,8 @@ class ReplicatedBagOStuff extends BagOStuff {
return $this->writeStore->decr( $key, $value );
}
public function lock( $key, $timeout = 6, $expiry = 6 ) {
return $this->writeStore->lock( $key, $timeout, $expiry );
public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
return $this->writeStore->lock( $key, $timeout, $expiry, $rclass );
}
public function unlock( $key ) {

5
includes/objectcache/MultiWriteBagOStuff.php
View file

@ -121,12 +121,13 @@ class MultiWriteBagOStuff extends BagOStuff {
* @param string $key
* @param int $timeout
* @param int $expiry
* @param string $rclass
* @return bool
*/
public function lock( $key, $timeout = 6, $expiry = 6 ) {
public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
// Lock only the first cache, to avoid deadlocks
if ( isset( $this->caches[0] ) ) {
return $this->caches[0]->lock( $key, $timeout, $expiry );
return $this->caches[0]->lock( $key, $timeout, $expiry, $rclass );
} else {
return true;
}

8
tests/phpunit/includes/objectcache/BagOStuffTest.php
View file

@ -1,6 +1,7 @@
<?php
/**
* @author Matthias Mullie <mmullie@wikimedia.org>
* @group BagOStuff
*/
class BagOStuffTest extends MediaWikiTestCase {
/** @var BagOStuff */
@ -169,5 +170,12 @@ class BagOStuffTest extends MediaWikiTestCase {
$value3 = $this->cache->getScopedLock( $key, 0 );
$this->assertType( 'ScopedCallback', $value3, 'Lock returned callback after release' );
unset( $value3 );
$value1 = $this->cache->getScopedLock( $key, 0, 5, 'reentry' );
$value2 = $this->cache->getScopedLock( $key, 0, 5, 'reentry' );
$this->assertType( 'ScopedCallback', $value1, 'First reentrant call returned lock' );
$this->assertType( 'ScopedCallback', $value1, 'Second reentrant call returned lock' );
}
}