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https://github.com/YunoHost-Apps/mediawiki_ynh.git
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432 lines
14 KiB
PHP
432 lines
14 KiB
PHP
<?php
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/**
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* Version of LockManager based on using DB table locks.
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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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* Version of LockManager based on using named/row DB locks.
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*
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* This is meant for multi-wiki systems that may share files.
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*
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* All lock requests for a resource, identified by a hash string, will map
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* to one bucket. Each bucket maps to one or several peer DBs, each on their
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* own server, all having the filelocks.sql tables (with row-level locking).
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* A majority of peer DBs must agree for a lock to be acquired.
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*
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* Caching is used to avoid hitting servers that are down.
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*
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* @ingroup LockManager
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* @since 1.19
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*/
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abstract class DBLockManager extends QuorumLockManager {
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/** @var Array Map of DB names to server config */
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protected $dbServers; // (DB name => server config array)
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/** @var BagOStuff */
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protected $statusCache;
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protected $lockExpiry; // integer number of seconds
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protected $safeDelay; // integer number of seconds
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protected $session = 0; // random integer
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/** @var Array Map Database connections (DB name => Database) */
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protected $conns = array();
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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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* - dbServers : Associative array of DB names to server configuration.
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* Configuration is an associative array that includes:
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* - host : DB server name
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* - dbname : DB name
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* - type : DB type (mysql,postgres,...)
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* - user : DB user
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* - password : DB user password
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* - tablePrefix : DB table prefix
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* - flags : DB flags (see DatabaseBase)
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* - dbsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
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* each having an odd-numbered list of DB names (peers) as values.
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* Any DB named 'localDBMaster' will automatically use the DB master
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* settings for this wiki (without the need for a dbServers entry).
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* Only use 'localDBMaster' if the domain is a valid wiki ID.
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* - lockExpiry : Lock timeout (seconds) for dropped connections. [optional]
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* This tells the DB server how long to wait before assuming
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* connection failure and releasing all the locks for a session.
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*
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* @param array $config
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*/
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public function __construct( array $config ) {
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parent::__construct( $config );
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$this->dbServers = isset( $config['dbServers'] )
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? $config['dbServers']
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: array(); // likely just using 'localDBMaster'
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// Sanitize srvsByBucket config to prevent PHP errors
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$this->srvsByBucket = array_filter( $config['dbsByBucket'], 'is_array' );
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$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
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if ( isset( $config['lockExpiry'] ) ) {
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$this->lockExpiry = $config['lockExpiry'];
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} else {
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$met = ini_get( 'max_execution_time' );
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$this->lockExpiry = $met ? $met : 60; // use some sane amount if 0
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}
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$this->safeDelay = ( $this->lockExpiry <= 0 )
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? 60 // pick a safe-ish number to match DB timeout default
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: $this->lockExpiry; // cover worst case
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foreach ( $this->srvsByBucket as $bucket ) {
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if ( count( $bucket ) > 1 ) { // multiple peers
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// Tracks peers that couldn't be queried recently to avoid lengthy
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// connection timeouts. This is useless if each bucket has one peer.
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try {
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$this->statusCache = ObjectCache::newAccelerator( array() );
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} catch ( MWException $e ) {
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trigger_error( __CLASS__ .
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" using multiple DB peers without apc, xcache, or wincache." );
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}
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break;
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}
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}
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$this->session = wfRandomString( 31 );
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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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foreach ( $pathsByType as $type => $paths ) {
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$status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
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}
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return $status;
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}
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protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
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return Status::newGood();
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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( $lockSrv ) {
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if ( !$this->cacheCheckFailures( $lockSrv ) ) {
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return false; // recent failure to connect
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}
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try {
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$this->getConnection( $lockSrv );
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} catch ( DBError $e ) {
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$this->cacheRecordFailure( $lockSrv );
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return false; // failed to connect
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}
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return true;
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}
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/**
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* Get (or reuse) a connection to a lock DB
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*
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* @param $lockDb string
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* @return DatabaseBase
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* @throws DBError
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*/
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protected function getConnection( $lockDb ) {
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if ( !isset( $this->conns[$lockDb] ) ) {
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$db = null;
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if ( $lockDb === 'localDBMaster' ) {
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$lb = wfGetLBFactory()->getMainLB( $this->domain );
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$db = $lb->getConnection( DB_MASTER, array(), $this->domain );
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} elseif ( isset( $this->dbServers[$lockDb] ) ) {
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$config = $this->dbServers[$lockDb];
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$db = DatabaseBase::factory( $config['type'], $config );
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}
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if ( !$db ) {
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return null; // config error?
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}
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$this->conns[$lockDb] = $db;
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$this->conns[$lockDb]->clearFlag( DBO_TRX );
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# If the connection drops, try to avoid letting the DB rollback
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# and release the locks before the file operations are finished.
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# This won't handle the case of DB server restarts however.
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$options = array();
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if ( $this->lockExpiry > 0 ) {
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$options['connTimeout'] = $this->lockExpiry;
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}
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$this->conns[$lockDb]->setSessionOptions( $options );
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$this->initConnection( $lockDb, $this->conns[$lockDb] );
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}
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if ( !$this->conns[$lockDb]->trxLevel() ) {
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$this->conns[$lockDb]->begin( __METHOD__ ); // start transaction
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}
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return $this->conns[$lockDb];
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}
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/**
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* Do additional initialization for new lock DB connection
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*
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* @param $lockDb string
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* @param $db DatabaseBase
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* @return void
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* @throws DBError
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*/
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protected function initConnection( $lockDb, DatabaseBase $db ) {}
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/**
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* Checks if the DB has not recently had connection/query errors.
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* This just avoids wasting time on doomed connection attempts.
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*
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* @param $lockDb string
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* @return bool
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*/
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protected function cacheCheckFailures( $lockDb ) {
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return ( $this->statusCache && $this->safeDelay > 0 )
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? !$this->statusCache->get( $this->getMissKey( $lockDb ) )
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: true;
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}
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/**
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* Log a lock request failure to the cache
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*
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* @param $lockDb string
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* @return bool Success
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*/
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protected function cacheRecordFailure( $lockDb ) {
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return ( $this->statusCache && $this->safeDelay > 0 )
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? $this->statusCache->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay )
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: true;
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}
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/**
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* Get a cache key for recent query misses for a DB
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*
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* @param $lockDb string
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* @return string
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*/
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protected function getMissKey( $lockDb ) {
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$lockDb = ( $lockDb === 'localDBMaster' ) ? wfWikiID() : $lockDb; // non-relative
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return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
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}
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/**
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* Make sure remaining locks get cleared for sanity
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*/
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function __destruct() {
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$this->releaseAllLocks();
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foreach ( $this->conns as $db ) {
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$db->close();
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}
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}
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}
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/**
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* MySQL version of DBLockManager that supports shared locks.
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* All locks are non-blocking, which avoids deadlocks.
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*
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* @ingroup LockManager
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*/
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class MySqlLockManager extends DBLockManager {
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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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/**
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* @param $lockDb string
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* @param $db DatabaseBase
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*/
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protected function initConnection( $lockDb, DatabaseBase $db ) {
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# Let this transaction see lock rows from other transactions
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$db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" );
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}
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/**
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* Get a connection to a lock DB and acquire locks on $paths.
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* This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118.
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*
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* @see DBLockManager::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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$db = $this->getConnection( $lockSrv ); // checked in isServerUp()
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$keys = array(); // list of hash keys for the paths
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$data = array(); // list of rows to insert
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$checkEXKeys = array(); // list of hash keys that this has no EX lock on
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# Build up values for INSERT clause
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foreach ( $paths as $path ) {
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$key = $this->sha1Base36Absolute( $path );
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$keys[] = $key;
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$data[] = array( 'fls_key' => $key, 'fls_session' => $this->session );
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if ( !isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
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$checkEXKeys[] = $key;
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}
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}
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# Block new writers (both EX and SH locks leave entries here)...
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$db->insert( 'filelocks_shared', $data, __METHOD__, array( 'IGNORE' ) );
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# Actually do the locking queries...
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if ( $type == self::LOCK_SH ) { // reader locks
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$blocked = false;
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# Bail if there are any existing writers...
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if ( count( $checkEXKeys ) ) {
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$blocked = $db->selectField( 'filelocks_exclusive', '1',
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array( 'fle_key' => $checkEXKeys ),
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__METHOD__
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);
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}
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# Other prospective writers that haven't yet updated filelocks_exclusive
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# will recheck filelocks_shared after doing so and bail due to this entry.
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} else { // writer locks
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$encSession = $db->addQuotes( $this->session );
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# Bail if there are any existing writers...
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# This may detect readers, but the safe check for them is below.
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# Note: if two writers come at the same time, both bail :)
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$blocked = $db->selectField( 'filelocks_shared', '1',
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array( 'fls_key' => $keys, "fls_session != $encSession" ),
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__METHOD__
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);
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if ( !$blocked ) {
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# Build up values for INSERT clause
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$data = array();
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foreach ( $keys as $key ) {
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$data[] = array( 'fle_key' => $key );
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}
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# Block new readers/writers...
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$db->insert( 'filelocks_exclusive', $data, __METHOD__ );
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# Bail if there are any existing readers...
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$blocked = $db->selectField( 'filelocks_shared', '1',
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array( 'fls_key' => $keys, "fls_session != $encSession" ),
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__METHOD__
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);
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}
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}
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if ( $blocked ) {
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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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}
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return $status;
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}
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/**
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* @see QuorumLockManager::releaseAllLocks()
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* @return Status
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*/
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protected function releaseAllLocks() {
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$status = Status::newGood();
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foreach ( $this->conns as $lockDb => $db ) {
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if ( $db->trxLevel() ) { // in transaction
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try {
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$db->rollback( __METHOD__ ); // finish transaction and kill any rows
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} catch ( DBError $e ) {
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$status->fatal( 'lockmanager-fail-db-release', $lockDb );
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}
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}
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}
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return $status;
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}
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}
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/**
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* PostgreSQL version of DBLockManager that supports shared locks.
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* All locks are non-blocking, which avoids deadlocks.
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*
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* @ingroup LockManager
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*/
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class PostgreSqlLockManager extends DBLockManager {
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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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protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
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$status = Status::newGood();
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if ( !count( $paths ) ) {
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return $status; // nothing to lock
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}
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$db = $this->getConnection( $lockSrv ); // checked in isServerUp()
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$bigints = array_unique( array_map(
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function( $key ) {
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return wfBaseConvert( substr( $key, 0, 15 ), 16, 10 );
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},
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array_map( array( $this, 'sha1Base16Absolute' ), $paths )
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) );
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// Try to acquire all the locks...
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$fields = array();
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foreach ( $bigints as $bigint ) {
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$fields[] = ( $type == self::LOCK_SH )
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? "pg_try_advisory_lock_shared({$db->addQuotes( $bigint )}) AS K$bigint"
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: "pg_try_advisory_lock({$db->addQuotes( $bigint )}) AS K$bigint";
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}
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$res = $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
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$row = (array)$res->fetchObject();
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if ( in_array( 'f', $row ) ) {
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// Release any acquired locks if some could not be acquired...
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$fields = array();
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foreach ( $row as $kbigint => $ok ) {
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if ( $ok === 't' ) { // locked
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$bigint = substr( $kbigint, 1 ); // strip off the "K"
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$fields[] = ( $type == self::LOCK_SH )
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? "pg_advisory_unlock_shared({$db->addQuotes( $bigint )})"
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: "pg_advisory_unlock({$db->addQuotes( $bigint )})";
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}
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}
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if ( count( $fields ) ) {
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$db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
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}
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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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}
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return $status;
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}
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/**
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* @see QuorumLockManager::releaseAllLocks()
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* @return Status
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*/
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protected function releaseAllLocks() {
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$status = Status::newGood();
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foreach ( $this->conns as $lockDb => $db ) {
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try {
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$db->query( "SELECT pg_advisory_unlock_all()", __METHOD__ );
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} catch ( DBError $e ) {
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$status->fatal( 'lockmanager-fail-db-release', $lockDb );
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}
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}
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return $status;
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}
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}
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