3 * Version of LockManager based on using DB table locks.
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License along
16 * with this program; if not, write to the Free Software Foundation, Inc.,
17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 * http://www.gnu.org/copyleft/gpl.html
21 * @ingroup LockManager
25 * Version of LockManager based on using named/row DB locks.
27 * This is meant for multi-wiki systems that may share files.
29 * All lock requests for a resource, identified by a hash string, will map to one bucket.
30 * Each bucket maps to one or several peer DBs, each on their own server.
31 * A majority of peer DBs must agree for a lock to be acquired.
33 * Caching is used to avoid hitting servers that are down.
35 * @ingroup LockManager
38 abstract class DBLockManager
extends QuorumLockManager
{
39 /** @var array[] Map of DB names to server config */
40 protected $dbServers; // (DB name => server config array)
42 protected $statusCache;
44 protected $lockExpiry; // integer number of seconds
45 protected $safeDelay; // integer number of seconds
47 protected $session = 0; // random integer
48 /** @var IDatabase[] Map Database connections (DB name => Database) */
49 protected $conns = [];
52 * Construct a new instance from configuration.
54 * @param array $config Parameters include:
55 * - dbServers : Associative array of DB names to server configuration.
56 * Configuration is an associative array that includes:
57 * - host : DB server name
59 * - type : DB type (mysql,postgres,...)
61 * - password : DB user password
62 * - tablePrefix : DB table prefix
63 * - flags : DB flags (see DatabaseBase)
64 * - dbsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
65 * each having an odd-numbered list of DB names (peers) as values.
66 * Any DB named 'localDBMaster' will automatically use the DB master
67 * settings for this wiki (without the need for a dbServers entry).
68 * Only use 'localDBMaster' if the domain is a valid wiki ID.
69 * - lockExpiry : Lock timeout (seconds) for dropped connections. [optional]
70 * This tells the DB server how long to wait before assuming
71 * connection failure and releasing all the locks for a session.
73 public function __construct( array $config ) {
74 parent
::__construct( $config );
76 $this->dbServers
= isset( $config['dbServers'] )
77 ?
$config['dbServers']
78 : []; // likely just using 'localDBMaster'
79 // Sanitize srvsByBucket config to prevent PHP errors
80 $this->srvsByBucket
= array_filter( $config['dbsByBucket'], 'is_array' );
81 $this->srvsByBucket
= array_values( $this->srvsByBucket
); // consecutive
83 if ( isset( $config['lockExpiry'] ) ) {
84 $this->lockExpiry
= $config['lockExpiry'];
86 $met = ini_get( 'max_execution_time' );
87 $this->lockExpiry
= $met ?
$met : 60; // use some sane amount if 0
89 $this->safeDelay
= ( $this->lockExpiry
<= 0 )
90 ?
60 // pick a safe-ish number to match DB timeout default
91 : $this->lockExpiry
; // cover worst case
93 foreach ( $this->srvsByBucket
as $bucket ) {
94 if ( count( $bucket ) > 1 ) { // multiple peers
95 // Tracks peers that couldn't be queried recently to avoid lengthy
96 // connection timeouts. This is useless if each bucket has one peer.
97 $this->statusCache
= ObjectCache
::getLocalServerInstance();
102 $this->session
= wfRandomString( 31 );
105 // @todo change this code to work in one batch
106 protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
107 $status = Status
::newGood();
108 foreach ( $pathsByType as $type => $paths ) {
109 $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
115 abstract protected function doGetLocksOnServer( $lockSrv, array $paths, $type );
117 protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
118 return Status
::newGood();
122 * @see QuorumLockManager::isServerUp()
123 * @param string $lockSrv
126 protected function isServerUp( $lockSrv ) {
127 if ( !$this->cacheCheckFailures( $lockSrv ) ) {
128 return false; // recent failure to connect
131 $this->getConnection( $lockSrv );
132 } catch ( DBError
$e ) {
133 $this->cacheRecordFailure( $lockSrv );
135 return false; // failed to connect
142 * Get (or reuse) a connection to a lock DB
144 * @param string $lockDb
147 * @throws UnexpectedValueException
149 protected function getConnection( $lockDb ) {
150 if ( !isset( $this->conns
[$lockDb] ) ) {
151 if ( $lockDb === 'localDBMaster' ) {
152 $lb = $this->getLocalLB();
153 $db = $lb->getConnection( DB_MASTER
, [], $this->domain
);
154 # Do not mess with settings if the LoadBalancer is the main singleton
155 # to avoid clobbering the settings of handles from wfGetDB( DB_MASTER ).
156 $init = ( wfGetLB() !== $lb );
157 } elseif ( isset( $this->dbServers
[$lockDb] ) ) {
158 $config = $this->dbServers
[$lockDb];
159 $db = DatabaseBase
::factory( $config['type'], $config );
162 throw new UnexpectedValueException( "No server called '$lockDb'." );
166 $db->clearFlag( DBO_TRX
);
167 # If the connection drops, try to avoid letting the DB rollback
168 # and release the locks before the file operations are finished.
169 # This won't handle the case of DB server restarts however.
171 if ( $this->lockExpiry
> 0 ) {
172 $options['connTimeout'] = $this->lockExpiry
;
174 $db->setSessionOptions( $options );
175 $this->initConnection( $lockDb, $db );
178 $this->conns
[$lockDb] = $db;
181 return $this->conns
[$lockDb];
185 * @return LoadBalancer
187 protected function getLocalLB() {
188 return wfGetLBFactory()->getMainLB( $this->domain
);
192 * Do additional initialization for new lock DB connection
194 * @param string $lockDb
195 * @param IDatabase $db
198 protected function initConnection( $lockDb, IDatabase
$db ) {
202 * Checks if the DB has not recently had connection/query errors.
203 * This just avoids wasting time on doomed connection attempts.
205 * @param string $lockDb
208 protected function cacheCheckFailures( $lockDb ) {
209 return ( $this->statusCache
&& $this->safeDelay
> 0 )
210 ?
!$this->statusCache
->get( $this->getMissKey( $lockDb ) )
215 * Log a lock request failure to the cache
217 * @param string $lockDb
218 * @return bool Success
220 protected function cacheRecordFailure( $lockDb ) {
221 return ( $this->statusCache
&& $this->safeDelay
> 0 )
222 ?
$this->statusCache
->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay
)
227 * Get a cache key for recent query misses for a DB
229 * @param string $lockDb
232 protected function getMissKey( $lockDb ) {
233 $lockDb = ( $lockDb === 'localDBMaster' ) ?
wfWikiID() : $lockDb; // non-relative
234 return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
238 * Make sure remaining locks get cleared for sanity
240 function __destruct() {
241 $this->releaseAllLocks();
242 foreach ( $this->conns
as $db ) {