06fc5ddb56
I set up a local test instance with RedisLockManager, but some things seemed more complicated than they needed to be. So: * Add lockManager option to $wgLocalFileRepo, which becomes the lockManager of the auto-generated file backend. * Made srvsByBucket be optional. I made the same change to the identical code in MemcLockManager and DBLockManager, but I didn't test them. * Improved doc comments for RedisLockManager::__construct() and $wgLocalFileRepo. Change-Id: I8ce430b8e849589d4ea87c90a56ee3659da085a0
361 lines
11 KiB
PHP
361 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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use Wikimedia\WaitConditionLoop;
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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 = [
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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 MemcachedBagOStuff[] Map of (server name => MemcachedBagOStuff) */
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protected $cacheServers = [];
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/** @var MapCacheLRU Server status cache */
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protected $statusCache;
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/**
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* Construct a new instance from configuration.
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*
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* @param array $config Parameters include:
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* - lockServers : Associative array of server names to "<IP>:<port>" strings.
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* - srvsByBucket : An array of up to 16 arrays, each containing the server names
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* in a bucket. Each bucket should have an odd number of servers.
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* If omitted, all servers will be in one bucket. [optional].
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* - memcConfig : Configuration array for MemcachedBagOStuff::construct() with an
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* additional 'class' parameter specifying which MemcachedBagOStuff
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* subclass to use. The server names will be injected. [optional]
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* @throws Exception
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*/
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public function __construct( array $config ) {
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parent::__construct( $config );
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if ( isset( $config['srvsByBucket'] ) ) {
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// Sanitize srvsByBucket config to prevent PHP errors
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$this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
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$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
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} else {
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$this->srvsByBucket = [ array_keys( $config['lockServers'] ) ];
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}
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$memcConfig = $config['memcConfig'] ?? [];
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$memcConfig += [ 'class' => MemcachedPhpBagOStuff::class ]; // default
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$class = $memcConfig['class'];
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if ( !is_subclass_of( $class, MemcachedBagOStuff::class ) ) {
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throw new InvalidArgumentException( "$class is not of type MemcachedBagOStuff." );
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}
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foreach ( $config['lockServers'] as $name => $address ) {
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$params = [ 'servers' => [ $address ] ] + $memcConfig;
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$this->cacheServers[$name] = new $class( $params );
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}
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$this->statusCache = new MapCacheLRU( 100 );
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}
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protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
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$status = StatusValue::newGood();
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$memc = $this->getCache( $lockSrv );
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// List of affected paths
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$paths = array_merge( ...array_values( $pathsByType ) );
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$paths = array_unique( $paths );
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// List of affected lock record keys
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$keys = array_map( [ $this, 'recordKeyForPath' ], $paths );
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// Lock all of the active lock record keys...
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if ( !$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 ( $pathsByType as $type => $paths ) {
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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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}
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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, $locksHeld, self::MAX_LOCK_TTL );
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if ( !$ok ) {
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$status->fatal( 'lockmanager-fail-acquirelock', $path );
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} else {
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$this->logger->debug( __METHOD__ . ": acquired lock on key $locksKey." );
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}
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}
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}
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// Unlock all of the active lock record keys...
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$this->releaseMutexes( $memc, $keys );
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return $status;
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}
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protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
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$status = StatusValue::newGood();
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$memc = $this->getCache( $lockSrv );
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// List of affected paths
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$paths = array_merge( ...array_values( $pathsByType ) );
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$paths = array_unique( $paths );
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// List of affected lock record keys
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$keys = array_map( [ $this, 'recordKeyForPath' ], $paths );
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// Lock all of the active lock record keys...
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if ( !$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 $status;
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}
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// Fetch all the existing lock records...
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$lockRecords = $memc->getMulti( $keys );
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// Remove the requested locks from all records...
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foreach ( $pathsByType as $type => $paths ) {
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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 = $this->sanitizeLockArray( $lockRecords[$locksKey] );
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if ( isset( $locksHeld[$type][$this->session] ) ) {
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unset( $locksHeld[$type][$this->session] ); // unregister this session
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$lockRecords[$locksKey] = $locksHeld;
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} else {
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$status->warning( 'lockmanager-fail-releaselock', $path );
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}
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}
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}
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// Persist the new lock record values...
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foreach ( $paths as $path ) {
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$locksKey = $this->recordKeyForPath( $path );
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if ( !isset( $lockRecords[$locksKey] ) ) {
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continue; // nothing to do
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}
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$locksHeld = $lockRecords[$locksKey];
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if ( $locksHeld === $this->newLockArray() ) {
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$ok = $memc->delete( $locksKey );
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} else {
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$ok = $memc->set( $locksKey, $locksHeld, self::MAX_LOCK_TTL );
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}
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if ( $ok ) {
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$this->logger->debug( __METHOD__ . ": released lock on key $locksKey." );
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} else {
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$status->fatal( 'lockmanager-fail-releaselock', $path );
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}
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}
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// Unlock all of the active lock record keys...
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$this->releaseMutexes( $memc, $keys );
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return $status;
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}
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/**
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* @see QuorumLockManager::releaseAllLocks()
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* @return StatusValue
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*/
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protected function releaseAllLocks() {
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return StatusValue::newGood(); // not supported
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}
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/**
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* @see QuorumLockManager::isServerUp()
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* @param string $lockSrv
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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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if ( !isset( $this->cacheServers[$lockSrv] ) ) {
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throw new InvalidArgumentException( "Invalid cache server '$lockSrv'." );
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}
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$online = $this->statusCache->get( "online:$lockSrv", 30 );
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if ( $online === null ) {
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$online = $this->cacheServers[$lockSrv]->set( __CLASS__ . ':ping', 1, 1 );
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if ( !$online ) { // server down?
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$this->logger->warning( __METHOD__ . ": Could not contact $lockSrv." );
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}
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$this->statusCache->set( "online:$lockSrv", (int)$online );
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}
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return $online ? $this->cacheServers[$lockSrv] : null;
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}
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/**
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* @param string $path
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* @return string
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*/
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protected function recordKeyForPath( $path ) {
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return implode( ':', [ __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 function newLockArray() {
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return [ self::LOCK_SH => [], self::LOCK_EX => [] ];
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}
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/**
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* @param array $a
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* @return array An empty lock structure for a key
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*/
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protected 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 $a;
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}
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$this->logger->error( __METHOD__ . ": reset invalid lock array." );
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return $this->newLockArray();
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}
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/**
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* @param MemcachedBagOStuff $memc
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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 = [];
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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( $keys );
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// Try to quickly loop to acquire the keys, but back off after a few rounds.
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// This reduces memcached spam, especially in the rare case where a server acquires
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// some lock keys and dies without releasing them. Lock keys expire after a few minutes.
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$loop = new WaitConditionLoop(
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static function () use ( $memc, $keys, &$lockedKeys ) {
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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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}
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}
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return array_diff( $keys, $lockedKeys )
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? WaitConditionLoop::CONDITION_CONTINUE
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: true;
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},
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3.0 // timeout
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);
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$loop->invoke();
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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 MemcachedBagOStuff $memc
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* @param array $keys List of acquired keys
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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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public 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( [ $path ], self::LOCK_EX );
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$this->doUnlock( [ $path ], self::LOCK_SH );
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}
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}
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}
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}
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