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
30 * to one bucket. Each bucket maps to one or several peer DBs, each on their
31 * own server, all having the filelocks.sql tables (with row-level locking).
32 * A majority of peer DBs must agree for a lock to be acquired.
34 * Caching is used to avoid hitting servers that are down.
36 * @ingroup LockManager
39 abstract class DBLockManager
extends QuorumLockManager
{
40 /** @var array[] Map of DB names to server config */
41 protected $dbServers; // (DB name => server config array)
43 protected $statusCache;
45 protected $lockExpiry; // integer number of seconds
46 protected $safeDelay; // integer number of seconds
48 protected $session = 0; // random integer
49 /** @var IDatabase[] Map Database connections (DB name => Database) */
50 protected $conns = [];
53 * Construct a new instance from configuration.
55 * @param array $config Parameters include:
56 * - dbServers : Associative array of DB names to server configuration.
57 * Configuration is an associative array that includes:
58 * - host : DB server name
60 * - type : DB type (mysql,postgres,...)
62 * - password : DB user password
63 * - tablePrefix : DB table prefix
64 * - flags : DB flags (see DatabaseBase)
65 * - dbsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
66 * each having an odd-numbered list of DB names (peers) as values.
67 * Any DB named 'localDBMaster' will automatically use the DB master
68 * settings for this wiki (without the need for a dbServers entry).
69 * Only use 'localDBMaster' if the domain is a valid wiki ID.
70 * - lockExpiry : Lock timeout (seconds) for dropped connections. [optional]
71 * This tells the DB server how long to wait before assuming
72 * connection failure and releasing all the locks for a session.
74 public function __construct( array $config ) {
75 parent
::__construct( $config );
77 $this->dbServers
= isset( $config['dbServers'] )
78 ?
$config['dbServers']
79 : []; // likely just using 'localDBMaster'
80 // Sanitize srvsByBucket config to prevent PHP errors
81 $this->srvsByBucket
= array_filter( $config['dbsByBucket'], 'is_array' );
82 $this->srvsByBucket
= array_values( $this->srvsByBucket
); // consecutive
84 if ( isset( $config['lockExpiry'] ) ) {
85 $this->lockExpiry
= $config['lockExpiry'];
87 $met = ini_get( 'max_execution_time' );
88 $this->lockExpiry
= $met ?
$met : 60; // use some sane amount if 0
90 $this->safeDelay
= ( $this->lockExpiry
<= 0 )
91 ?
60 // pick a safe-ish number to match DB timeout default
92 : $this->lockExpiry
; // cover worst case
94 foreach ( $this->srvsByBucket
as $bucket ) {
95 if ( count( $bucket ) > 1 ) { // multiple peers
96 // Tracks peers that couldn't be queried recently to avoid lengthy
97 // connection timeouts. This is useless if each bucket has one peer.
98 $this->statusCache
= ObjectCache
::getLocalServerInstance();
103 $this->session
= wfRandomString( 31 );
106 // @todo change this code to work in one batch
107 protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
108 $status = Status
::newGood();
109 foreach ( $pathsByType as $type => $paths ) {
110 $status->merge( $this->doGetLocksOnServer( $lockSrv, $paths, $type ) );
116 abstract protected function doGetLocksOnServer( $lockSrv, array $paths, $type );
118 protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
119 return Status
::newGood();
123 * @see QuorumLockManager::isServerUp()
124 * @param string $lockSrv
127 protected function isServerUp( $lockSrv ) {
128 if ( !$this->cacheCheckFailures( $lockSrv ) ) {
129 return false; // recent failure to connect
132 $this->getConnection( $lockSrv );
133 } catch ( DBError
$e ) {
134 $this->cacheRecordFailure( $lockSrv );
136 return false; // failed to connect
143 * Get (or reuse) a connection to a lock DB
145 * @param string $lockDb
149 protected function getConnection( $lockDb ) {
150 if ( !isset( $this->conns
[$lockDb] ) ) {
152 if ( $lockDb === 'localDBMaster' ) {
153 $db = $this->getLocalLB()->getConnection( DB_MASTER
, [], $this->domain
);
154 } elseif ( isset( $this->dbServers
[$lockDb] ) ) {
155 $config = $this->dbServers
[$lockDb];
156 $db = DatabaseBase
::factory( $config['type'], $config );
159 return null; // config error?
161 $this->conns
[$lockDb] = $db;
162 $this->conns
[$lockDb]->clearFlag( DBO_TRX
);
163 # If the connection drops, try to avoid letting the DB rollback
164 # and release the locks before the file operations are finished.
165 # This won't handle the case of DB server restarts however.
167 if ( $this->lockExpiry
> 0 ) {
168 $options['connTimeout'] = $this->lockExpiry
;
170 $this->conns
[$lockDb]->setSessionOptions( $options );
171 $this->initConnection( $lockDb, $this->conns
[$lockDb] );
173 if ( !$this->conns
[$lockDb]->trxLevel() ) {
174 $this->conns
[$lockDb]->begin( __METHOD__
); // start transaction
177 return $this->conns
[$lockDb];
181 * @return LoadBalancer
183 protected function getLocalLB() {
184 return wfGetLBFactory()->getMainLB( $this->domain
);
188 * Do additional initialization for new lock DB connection
190 * @param string $lockDb
191 * @param IDatabase $db
194 protected function initConnection( $lockDb, IDatabase
$db ) {
198 * Checks if the DB has not recently had connection/query errors.
199 * This just avoids wasting time on doomed connection attempts.
201 * @param string $lockDb
204 protected function cacheCheckFailures( $lockDb ) {
205 return ( $this->statusCache
&& $this->safeDelay
> 0 )
206 ?
!$this->statusCache
->get( $this->getMissKey( $lockDb ) )
211 * Log a lock request failure to the cache
213 * @param string $lockDb
214 * @return bool Success
216 protected function cacheRecordFailure( $lockDb ) {
217 return ( $this->statusCache
&& $this->safeDelay
> 0 )
218 ?
$this->statusCache
->set( $this->getMissKey( $lockDb ), 1, $this->safeDelay
)
223 * Get a cache key for recent query misses for a DB
225 * @param string $lockDb
228 protected function getMissKey( $lockDb ) {
229 $lockDb = ( $lockDb === 'localDBMaster' ) ?
wfWikiID() : $lockDb; // non-relative
230 return 'dblockmanager:downservers:' . str_replace( ' ', '_', $lockDb );
234 * Make sure remaining locks get cleared for sanity
236 function __destruct() {
237 $this->releaseAllLocks();
238 foreach ( $this->conns
as $db ) {
245 * MySQL version of DBLockManager that supports shared locks.
246 * All locks are non-blocking, which avoids deadlocks.
248 * @ingroup LockManager
250 class MySqlLockManager
extends DBLockManager
{
251 /** @var array Mapping of lock types to the type actually used */
252 protected $lockTypeMap = [
253 self
::LOCK_SH
=> self
::LOCK_SH
,
254 self
::LOCK_UW
=> self
::LOCK_SH
,
255 self
::LOCK_EX
=> self
::LOCK_EX
258 protected function getLocalLB() {
259 // Use a separate connection so releaseAllLocks() doesn't rollback the main trx
260 return wfGetLBFactory()->newMainLB( $this->domain
);
263 protected function initConnection( $lockDb, IDatabase
$db ) {
264 # Let this transaction see lock rows from other transactions
265 $db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" );
269 * Get a connection to a lock DB and acquire locks on $paths.
270 * This does not use GET_LOCK() per http://bugs.mysql.com/bug.php?id=1118.
272 * @see DBLockManager::getLocksOnServer()
273 * @param string $lockSrv
274 * @param array $paths
275 * @param string $type
278 protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
279 $status = Status
::newGood();
281 $db = $this->getConnection( $lockSrv ); // checked in isServerUp()
283 $keys = []; // list of hash keys for the paths
284 $data = []; // list of rows to insert
285 $checkEXKeys = []; // list of hash keys that this has no EX lock on
286 # Build up values for INSERT clause
287 foreach ( $paths as $path ) {
288 $key = $this->sha1Base36Absolute( $path );
290 $data[] = [ 'fls_key' => $key, 'fls_session' => $this->session
];
291 if ( !isset( $this->locksHeld
[$path][self
::LOCK_EX
] ) ) {
292 $checkEXKeys[] = $key;
296 # Block new writers (both EX and SH locks leave entries here)...
297 $db->insert( 'filelocks_shared', $data, __METHOD__
, [ 'IGNORE' ] );
298 # Actually do the locking queries...
299 if ( $type == self
::LOCK_SH
) { // reader locks
301 # Bail if there are any existing writers...
302 if ( count( $checkEXKeys ) ) {
303 $blocked = $db->selectField( 'filelocks_exclusive', '1',
304 [ 'fle_key' => $checkEXKeys ],
308 # Other prospective writers that haven't yet updated filelocks_exclusive
309 # will recheck filelocks_shared after doing so and bail due to this entry.
310 } else { // writer locks
311 $encSession = $db->addQuotes( $this->session
);
312 # Bail if there are any existing writers...
313 # This may detect readers, but the safe check for them is below.
314 # Note: if two writers come at the same time, both bail :)
315 $blocked = $db->selectField( 'filelocks_shared', '1',
316 [ 'fls_key' => $keys, "fls_session != $encSession" ],
320 # Build up values for INSERT clause
322 foreach ( $keys as $key ) {
323 $data[] = [ 'fle_key' => $key ];
325 # Block new readers/writers...
326 $db->insert( 'filelocks_exclusive', $data, __METHOD__
);
327 # Bail if there are any existing readers...
328 $blocked = $db->selectField( 'filelocks_shared', '1',
329 [ 'fls_key' => $keys, "fls_session != $encSession" ],
336 foreach ( $paths as $path ) {
337 $status->fatal( 'lockmanager-fail-acquirelock', $path );
345 * @see QuorumLockManager::releaseAllLocks()
348 protected function releaseAllLocks() {
349 $status = Status
::newGood();
351 foreach ( $this->conns
as $lockDb => $db ) {
352 if ( $db->trxLevel() ) { // in transaction
354 $db->rollback( __METHOD__
); // finish transaction and kill any rows
355 } catch ( DBError
$e ) {
356 $status->fatal( 'lockmanager-fail-db-release', $lockDb );
366 * PostgreSQL version of DBLockManager that supports shared locks.
367 * All locks are non-blocking, which avoids deadlocks.
369 * @ingroup LockManager
371 class PostgreSqlLockManager
extends DBLockManager
{
372 /** @var array Mapping of lock types to the type actually used */
373 protected $lockTypeMap = [
374 self
::LOCK_SH
=> self
::LOCK_SH
,
375 self
::LOCK_UW
=> self
::LOCK_SH
,
376 self
::LOCK_EX
=> self
::LOCK_EX
379 protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
380 $status = Status
::newGood();
381 if ( !count( $paths ) ) {
382 return $status; // nothing to lock
385 $db = $this->getConnection( $lockSrv ); // checked in isServerUp()
386 $bigints = array_unique( array_map(
388 return Wikimedia\base_convert
( substr( $key, 0, 15 ), 16, 10 );
390 array_map( [ $this, 'sha1Base16Absolute' ], $paths )
393 // Try to acquire all the locks...
395 foreach ( $bigints as $bigint ) {
396 $fields[] = ( $type == self
::LOCK_SH
)
397 ?
"pg_try_advisory_lock_shared({$db->addQuotes( $bigint )}) AS K$bigint"
398 : "pg_try_advisory_lock({$db->addQuotes( $bigint )}) AS K$bigint";
400 $res = $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__
);
401 $row = $res->fetchRow();
403 if ( in_array( 'f', $row ) ) {
404 // Release any acquired locks if some could not be acquired...
406 foreach ( $row as $kbigint => $ok ) {
407 if ( $ok === 't' ) { // locked
408 $bigint = substr( $kbigint, 1 ); // strip off the "K"
409 $fields[] = ( $type == self
::LOCK_SH
)
410 ?
"pg_advisory_unlock_shared({$db->addQuotes( $bigint )})"
411 : "pg_advisory_unlock({$db->addQuotes( $bigint )})";
414 if ( count( $fields ) ) {
415 $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__
);
417 foreach ( $paths as $path ) {
418 $status->fatal( 'lockmanager-fail-acquirelock', $path );
426 * @see QuorumLockManager::releaseAllLocks()
429 protected function releaseAllLocks() {
430 $status = Status
::newGood();
432 foreach ( $this->conns
as $lockDb => $db ) {
434 $db->query( "SELECT pg_advisory_unlock_all()", __METHOD__
);
435 } catch ( DBError
$e ) {
436 $status->fatal( 'lockmanager-fail-db-release', $lockDb );