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https://github.com/YunoHost-Apps/mediawiki_ynh.git
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374 lines
11 KiB
PHP
374 lines
11 KiB
PHP
<?php
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/**
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* Version of LockManager based on using memcached servers.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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* @ingroup LockManager
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*/
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/**
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* Manage locks using memcached servers.
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*
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* Version of LockManager based on using memcached servers.
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* This is meant for multi-wiki systems that may share files.
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* All locks are non-blocking, which avoids deadlocks.
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*
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* All lock requests for a resource, identified by a hash string, will map to one
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* bucket. Each bucket maps to one or several peer servers, each running memcached.
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* A majority of peers must agree for a lock to be acquired.
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*
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* @ingroup LockManager
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* @since 1.20
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*/
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class MemcLockManager extends QuorumLockManager {
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/** @var Array Mapping of lock types to the type actually used */
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protected $lockTypeMap = array(
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self::LOCK_SH => self::LOCK_SH,
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self::LOCK_UW => self::LOCK_SH,
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self::LOCK_EX => self::LOCK_EX
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);
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/** @var Array Map server names to MemcachedBagOStuff objects */
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protected $bagOStuffs = array();
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/** @var Array */
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protected $serversUp = array(); // (server name => bool)
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protected $session = ''; // string; random UUID
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/**
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* Construct a new instance from configuration.
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*
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* $config paramaters include:
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* - lockServers : Associative array of server names to "<IP>:<port>" strings.
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* - srvsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
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* each having an odd-numbered list of server names (peers) as values.
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* - memcConfig : Configuration array for ObjectCache::newFromParams. [optional]
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* If set, this must use one of the memcached classes.
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*
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* @param array $config
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* @throws MWException
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*/
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public function __construct( array $config ) {
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parent::__construct( $config );
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// Sanitize srvsByBucket config to prevent PHP errors
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$this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
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$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
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$memcConfig = isset( $config['memcConfig'] )
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? $config['memcConfig']
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: array( 'class' => 'MemcachedPhpBagOStuff' );
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foreach ( $config['lockServers'] as $name => $address ) {
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$params = array( 'servers' => array( $address ) ) + $memcConfig;
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$cache = ObjectCache::newFromParams( $params );
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if ( $cache instanceof MemcachedBagOStuff ) {
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$this->bagOStuffs[$name] = $cache;
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} else {
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throw new MWException(
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'Only MemcachedBagOStuff classes are supported by MemcLockManager.' );
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}
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}
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$this->session = wfRandomString( 32 );
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}
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// @TODO: change this code to work in one batch
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protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
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$status = Status::newGood();
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$lockedPaths = array();
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foreach ( $pathsByType as $type => $paths ) {
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$status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
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if ( $status->isOK() ) {
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$lockedPaths[$type] = isset( $lockedPaths[$type] )
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? array_merge( $lockedPaths[$type], $paths )
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: $paths;
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} else {
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foreach ( $lockedPaths as $type => $paths ) {
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$status->merge( $this->doFreeLocksOnServer( $lockSrv, $paths, $type ) );
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}
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break;
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}
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}
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return $status;
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}
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// @TODO: change this code to work in one batch
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protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
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$status = Status::newGood();
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foreach ( $pathsByType as $type => $paths ) {
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$status->merge( $this->doFreeLocksOnServer( $lockSrv, $paths, $type ) );
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}
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return $status;
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}
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/**
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* @see QuorumLockManager::getLocksOnServer()
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* @return Status
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*/
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protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
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$status = Status::newGood();
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$memc = $this->getCache( $lockSrv );
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$keys = array_map( array( $this, 'recordKeyForPath' ), $paths ); // lock records
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// Lock all of the active lock record keys...
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if ( !$this->acquireMutexes( $memc, $keys ) ) {
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foreach ( $paths as $path ) {
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$status->fatal( 'lockmanager-fail-acquirelock', $path );
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}
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return $status;
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}
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// Fetch all the existing lock records...
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$lockRecords = $memc->getMulti( $keys );
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$now = time();
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// Check if the requested locks conflict with existing ones...
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foreach ( $paths as $path ) {
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$locksKey = $this->recordKeyForPath( $path );
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$locksHeld = isset( $lockRecords[$locksKey] )
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? self::sanitizeLockArray( $lockRecords[$locksKey] )
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: self::newLockArray(); // init
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foreach ( $locksHeld[self::LOCK_EX] as $session => $expiry ) {
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if ( $expiry < $now ) { // stale?
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unset( $locksHeld[self::LOCK_EX][$session] );
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} elseif ( $session !== $this->session ) {
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$status->fatal( 'lockmanager-fail-acquirelock', $path );
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}
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}
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if ( $type === self::LOCK_EX ) {
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foreach ( $locksHeld[self::LOCK_SH] as $session => $expiry ) {
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if ( $expiry < $now ) { // stale?
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unset( $locksHeld[self::LOCK_SH][$session] );
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} elseif ( $session !== $this->session ) {
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$status->fatal( 'lockmanager-fail-acquirelock', $path );
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}
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}
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}
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if ( $status->isOK() ) {
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// Register the session in the lock record array
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$locksHeld[$type][$this->session] = $now + $this->lockTTL;
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// We will update this record if none of the other locks conflict
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$lockRecords[$locksKey] = $locksHeld;
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}
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}
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// If there were no lock conflicts, update all the lock records...
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if ( $status->isOK() ) {
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foreach ( $paths as $path ) {
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$locksKey = $this->recordKeyForPath( $path );
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$locksHeld = $lockRecords[$locksKey];
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$ok = $memc->set( $locksKey, $locksHeld, 7 * 86400 );
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if ( !$ok ) {
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$status->fatal( 'lockmanager-fail-acquirelock', $path );
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} else {
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wfDebug( __METHOD__ . ": acquired lock on key $locksKey.\n" );
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}
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}
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}
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// Unlock all of the active lock record keys...
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$this->releaseMutexes( $memc, $keys );
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return $status;
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}
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/**
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* @see QuorumLockManager::freeLocksOnServer()
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* @return Status
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*/
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protected function doFreeLocksOnServer( $lockSrv, array $paths, $type ) {
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$status = Status::newGood();
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$memc = $this->getCache( $lockSrv );
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$keys = array_map( array( $this, 'recordKeyForPath' ), $paths ); // lock records
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// Lock all of the active lock record keys...
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if ( !$this->acquireMutexes( $memc, $keys ) ) {
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foreach ( $paths as $path ) {
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$status->fatal( 'lockmanager-fail-releaselock', $path );
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}
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return;
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}
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// Fetch all the existing lock records...
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$lockRecords = $memc->getMulti( $keys );
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// Remove the requested locks from all records...
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foreach ( $paths as $path ) {
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$locksKey = $this->recordKeyForPath( $path ); // lock record
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if ( !isset( $lockRecords[$locksKey] ) ) {
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$status->warning( 'lockmanager-fail-releaselock', $path );
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continue; // nothing to do
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}
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$locksHeld = self::sanitizeLockArray( $lockRecords[$locksKey] );
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if ( isset( $locksHeld[$type][$this->session] ) ) {
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unset( $locksHeld[$type][$this->session] ); // unregister this session
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if ( $locksHeld === self::newLockArray() ) {
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$ok = $memc->delete( $locksKey );
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} else {
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$ok = $memc->set( $locksKey, $locksHeld );
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}
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if ( !$ok ) {
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$status->fatal( 'lockmanager-fail-releaselock', $path );
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}
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} else {
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$status->warning( 'lockmanager-fail-releaselock', $path );
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}
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wfDebug( __METHOD__ . ": released lock on key $locksKey.\n" );
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}
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// Unlock all of the active lock record keys...
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$this->releaseMutexes( $memc, $keys );
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return $status;
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}
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/**
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* @see QuorumLockManager::releaseAllLocks()
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* @return Status
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*/
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protected function releaseAllLocks() {
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return Status::newGood(); // not supported
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}
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/**
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* @see QuorumLockManager::isServerUp()
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* @return bool
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*/
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protected function isServerUp( $lockSrv ) {
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return (bool)$this->getCache( $lockSrv );
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}
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/**
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* Get the MemcachedBagOStuff object for a $lockSrv
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*
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* @param string $lockSrv Server name
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* @return MemcachedBagOStuff|null
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*/
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protected function getCache( $lockSrv ) {
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$memc = null;
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if ( isset( $this->bagOStuffs[$lockSrv] ) ) {
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$memc = $this->bagOStuffs[$lockSrv];
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if ( !isset( $this->serversUp[$lockSrv] ) ) {
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$this->serversUp[$lockSrv] = $memc->set( __CLASS__ . ':ping', 1, 1 );
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if ( !$this->serversUp[$lockSrv] ) {
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trigger_error( __METHOD__ . ": Could not contact $lockSrv.", E_USER_WARNING );
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}
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}
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if ( !$this->serversUp[$lockSrv] ) {
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return null; // server appears to be down
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}
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}
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return $memc;
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}
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/**
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* @param $path string
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* @return string
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*/
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protected function recordKeyForPath( $path ) {
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return implode( ':', array( __CLASS__, 'locks', $this->sha1Base36Absolute( $path ) ) );
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}
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/**
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* @return Array An empty lock structure for a key
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*/
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protected static function newLockArray() {
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return array( self::LOCK_SH => array(), self::LOCK_EX => array() );
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}
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/**
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* @param $a array
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* @return Array An empty lock structure for a key
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*/
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protected static function sanitizeLockArray( $a ) {
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if ( is_array( $a ) && isset( $a[self::LOCK_EX] ) && isset( $a[self::LOCK_SH] ) ) {
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return $a;
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} else {
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trigger_error( __METHOD__ . ": reset invalid lock array.", E_USER_WARNING );
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return self::newLockArray();
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}
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}
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/**
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* @param $memc MemcachedBagOStuff
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* @param array $keys List of keys to acquire
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* @return bool
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*/
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protected function acquireMutexes( MemcachedBagOStuff $memc, array $keys ) {
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$lockedKeys = array();
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// Acquire the keys in lexicographical order, to avoid deadlock problems.
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// If P1 is waiting to acquire a key P2 has, P2 can't also be waiting for a key P1 has.
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sort( $keys );
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// Try to quickly loop to acquire the keys, but back off after a few rounds.
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// This reduces memcached spam, especially in the rare case where a server acquires
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// some lock keys and dies without releasing them. Lock keys expire after a few minutes.
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$rounds = 0;
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$start = microtime( true );
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do {
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if ( ( ++$rounds % 4 ) == 0 ) {
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usleep( 1000 * 50 ); // 50 ms
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}
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foreach ( array_diff( $keys, $lockedKeys ) as $key ) {
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if ( $memc->add( "$key:mutex", 1, 180 ) ) { // lock record
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$lockedKeys[] = $key;
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} else {
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continue; // acquire in order
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}
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}
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} while ( count( $lockedKeys ) < count( $keys ) && ( microtime( true ) - $start ) <= 3 );
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if ( count( $lockedKeys ) != count( $keys ) ) {
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$this->releaseMutexes( $memc, $lockedKeys ); // failed; release what was locked
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return false;
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}
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return true;
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}
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/**
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* @param $memc MemcachedBagOStuff
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* @param array $keys List of acquired keys
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* @return void
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*/
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protected function releaseMutexes( MemcachedBagOStuff $memc, array $keys ) {
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foreach ( $keys as $key ) {
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$memc->delete( "$key:mutex" );
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}
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}
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/**
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* Make sure remaining locks get cleared for sanity
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*/
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function __destruct() {
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while ( count( $this->locksHeld ) ) {
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foreach ( $this->locksHeld as $path => $locks ) {
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$this->doUnlock( array( $path ), self::LOCK_EX );
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$this->doUnlock( array( $path ), self::LOCK_SH );
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}
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}
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}
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}
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