3 * Database load balancing manager
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
23 namespace Wikimedia\Rdbms
;
25 use Psr\Log\LoggerInterface
;
26 use Psr\Log\NullLogger
;
27 use Wikimedia\ScopedCallback
;
32 use InvalidArgumentException
;
37 * Database connection, tracking, load balancing, and transaction manager for a cluster
41 class LoadBalancer
implements ILoadBalancer
{
42 /** @var array[] Map of (server index => server config array) */
44 /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
46 /** @var float[] Map of (server index => weight) */
48 /** @var array[] Map of (group => server index => weight) */
50 /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
51 private $mAllowLagged;
52 /** @var integer Seconds to spend waiting on replica DB lag to resolve */
53 private $mWaitTimeout;
54 /** @var array The LoadMonitor configuration */
55 private $loadMonitorConfig;
56 /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
57 private $tableAliases = [];
59 /** @var ILoadMonitor */
61 /** @var ChronologyProtector|null */
65 /** @var WANObjectCache */
67 /** @var object|string Class name or object With profileIn/profileOut methods */
69 /** @var TransactionProfiler */
70 protected $trxProfiler;
71 /** @var LoggerInterface */
72 protected $replLogger;
73 /** @var LoggerInterface */
74 protected $connLogger;
75 /** @var LoggerInterface */
76 protected $queryLogger;
77 /** @var LoggerInterface */
78 protected $perfLogger;
80 /** @var Database DB connection object that caused a problem */
81 private $errorConnection;
82 /** @var integer The generic (not query grouped) replica DB index (of $mServers) */
84 /** @var bool|DBMasterPos False if not set */
86 /** @var bool Whether the generic reader fell back to a lagged replica DB */
87 private $laggedReplicaMode = false;
88 /** @var bool Whether the generic reader fell back to a lagged replica DB */
89 private $allReplicasDownMode = false;
90 /** @var string The last DB selection or connection error */
91 private $mLastError = 'Unknown error';
92 /** @var string|bool Reason the LB is read-only or false if not */
93 private $readOnlyReason = false;
94 /** @var integer Total connections opened */
95 private $connsOpened = 0;
96 /** @var string|bool String if a requested DBO_TRX transaction round is active */
97 private $trxRoundId = false;
98 /** @var array[] Map of (name => callable) */
99 private $trxRecurringCallbacks = [];
100 /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
101 private $localDomain;
102 /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
103 private $localDomainIdAlias;
104 /** @var string Current server name */
106 /** @var bool Whether this PHP instance is for a CLI script */
108 /** @var string Agent name for query profiling */
111 /** @var callable Exception logger */
112 private $errorLogger;
115 private $disabled = false;
117 private $chronProtInitialized = false;
119 /** @var integer Warn when this many connection are held */
120 const CONN_HELD_WARN_THRESHOLD
= 10;
122 /** @var integer Default 'max lag' when unspecified */
123 const MAX_LAG_DEFAULT
= 10;
124 /** @var integer Seconds to cache master server read-only status */
125 const TTL_CACHE_READONLY
= 5;
127 const KEY_LOCAL
= 'local';
128 const KEY_FOREIGN_FREE
= 'foreignFree';
129 const KEY_FOREIGN_INUSE
= 'foreignInUse';
131 const KEY_LOCAL_NOROUND
= 'localAutoCommit';
132 const KEY_FOREIGN_FREE_NOROUND
= 'foreignFreeAutoCommit';
133 const KEY_FOREIGN_INUSE_NOROUND
= 'foreignInUseAutoCommit';
135 public function __construct( array $params ) {
136 if ( !isset( $params['servers'] ) ) {
137 throw new InvalidArgumentException( __CLASS__
. ': missing servers parameter' );
139 $this->mServers
= $params['servers'];
140 foreach ( $this->mServers
as $i => $server ) {
142 $this->mServers
[$i]['master'] = true;
144 $this->mServers
[$i]['replica'] = true;
148 $this->localDomain
= isset( $params['localDomain'] )
149 ? DatabaseDomain
::newFromId( $params['localDomain'] )
150 : DatabaseDomain
::newUnspecified();
151 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
152 // always true, gracefully handle the case when they fail to account for escaping.
153 if ( $this->localDomain
->getTablePrefix() != '' ) {
154 $this->localDomainIdAlias
=
155 $this->localDomain
->getDatabase() . '-' . $this->localDomain
->getTablePrefix();
157 $this->localDomainIdAlias
= $this->localDomain
->getDatabase();
160 $this->mWaitTimeout
= isset( $params['waitTimeout'] ) ?
$params['waitTimeout'] : 10;
162 $this->mReadIndex
= -1;
164 // Connection were transaction rounds may be applied
165 self
::KEY_LOCAL
=> [],
166 self
::KEY_FOREIGN_INUSE
=> [],
167 self
::KEY_FOREIGN_FREE
=> [],
168 // Auto-committing counterpart connections that ignore transaction rounds
169 self
::KEY_LOCAL_NOROUND
=> [],
170 self
::KEY_FOREIGN_INUSE_NOROUND
=> [],
171 self
::KEY_FOREIGN_FREE_NOROUND
=> []
174 $this->mWaitForPos
= false;
175 $this->mAllowLagged
= false;
177 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
178 $this->readOnlyReason
= $params['readOnlyReason'];
181 if ( isset( $params['loadMonitor'] ) ) {
182 $this->loadMonitorConfig
= $params['loadMonitor'];
184 $this->loadMonitorConfig
= [ 'class' => 'LoadMonitorNull' ];
187 foreach ( $params['servers'] as $i => $server ) {
188 $this->mLoads
[$i] = $server['load'];
189 if ( isset( $server['groupLoads'] ) ) {
190 foreach ( $server['groupLoads'] as $group => $ratio ) {
191 if ( !isset( $this->mGroupLoads
[$group] ) ) {
192 $this->mGroupLoads
[$group] = [];
194 $this->mGroupLoads
[$group][$i] = $ratio;
199 if ( isset( $params['srvCache'] ) ) {
200 $this->srvCache
= $params['srvCache'];
202 $this->srvCache
= new EmptyBagOStuff();
204 if ( isset( $params['wanCache'] ) ) {
205 $this->wanCache
= $params['wanCache'];
207 $this->wanCache
= WANObjectCache
::newEmpty();
209 $this->profiler
= isset( $params['profiler'] ) ?
$params['profiler'] : null;
210 if ( isset( $params['trxProfiler'] ) ) {
211 $this->trxProfiler
= $params['trxProfiler'];
213 $this->trxProfiler
= new TransactionProfiler();
216 $this->errorLogger
= isset( $params['errorLogger'] )
217 ?
$params['errorLogger']
218 : function ( Exception
$e ) {
219 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING
);
222 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
223 $this->$key = isset( $params[$key] ) ?
$params[$key] : new NullLogger();
226 $this->host
= isset( $params['hostname'] )
227 ?
$params['hostname']
228 : ( gethostname() ?
: 'unknown' );
229 $this->cliMode
= isset( $params['cliMode'] ) ?
$params['cliMode'] : PHP_SAPI
=== 'cli';
230 $this->agent
= isset( $params['agent'] ) ?
$params['agent'] : '';
232 if ( isset( $params['chronologyProtector'] ) ) {
233 $this->chronProt
= $params['chronologyProtector'];
238 * Get a LoadMonitor instance
240 * @return ILoadMonitor
242 private function getLoadMonitor() {
243 if ( !isset( $this->loadMonitor
) ) {
245 'LoadMonitor' => LoadMonitor
::class,
246 'LoadMonitorNull' => LoadMonitorNull
::class,
247 'LoadMonitorMySQL' => LoadMonitorMySQL
::class,
250 $class = $this->loadMonitorConfig
['class'];
251 if ( isset( $compat[$class] ) ) {
252 $class = $compat[$class];
255 $this->loadMonitor
= new $class(
256 $this, $this->srvCache
, $this->wanCache
, $this->loadMonitorConfig
);
257 $this->loadMonitor
->setLogger( $this->replLogger
);
260 return $this->loadMonitor
;
264 * @param array $loads
265 * @param bool|string $domain Domain to get non-lagged for
266 * @param int $maxLag Restrict the maximum allowed lag to this many seconds
267 * @return bool|int|string
269 private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF
) {
270 $lags = $this->getLagTimes( $domain );
272 # Unset excessively lagged servers
273 foreach ( $lags as $i => $lag ) {
275 # How much lag this server nominally is allowed to have
276 $maxServerLag = isset( $this->mServers
[$i]['max lag'] )
277 ?
$this->mServers
[$i]['max lag']
278 : self
::MAX_LAG_DEFAULT
; // default
279 # Constrain that futher by $maxLag argument
280 $maxServerLag = min( $maxServerLag, $maxLag );
282 $host = $this->getServerName( $i );
283 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
284 $this->replLogger
->error(
285 "Server {host} is not replicating?", [ 'host' => $host ] );
287 } elseif ( $lag > $maxServerLag ) {
288 $this->replLogger
->warning(
289 "Server {host} has {lag} seconds of lag (>= {maxlag})",
290 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
297 # Find out if all the replica DBs with non-zero load are lagged
299 foreach ( $loads as $load ) {
303 # No appropriate DB servers except maybe the master and some replica DBs with zero load
304 # Do NOT use the master
305 # Instead, this function will return false, triggering read-only mode,
306 # and a lagged replica DB will be used instead.
310 if ( count( $loads ) == 0 ) {
314 # Return a random representative of the remainder
315 return ArrayUtils
::pickRandom( $loads );
318 public function getReaderIndex( $group = false, $domain = false ) {
319 if ( count( $this->mServers
) == 1 ) {
320 // Skip the load balancing if there's only one server
321 return $this->getWriterIndex();
322 } elseif ( $group === false && $this->mReadIndex
>= 0 ) {
323 // Shortcut if the generic reader index was already cached
324 return $this->mReadIndex
;
327 if ( $group !== false ) {
328 // Use the server weight array for this load group
329 if ( isset( $this->mGroupLoads
[$group] ) ) {
330 $loads = $this->mGroupLoads
[$group];
332 // No loads for this group, return false and the caller can use some other group
333 $this->connLogger
->info( __METHOD__
. ": no loads for group $group" );
338 // Use the generic load group
339 $loads = $this->mLoads
;
342 // Scale the configured load ratios according to each server's load and state
343 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
345 // Pick a server to use, accounting for weights, load, lag, and mWaitForPos
346 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
347 if ( $i === false ) {
348 // Replica DB connection unsuccessful
352 if ( $this->mWaitForPos
&& $i != $this->getWriterIndex() ) {
353 // Before any data queries are run, wait for the server to catch up to the
354 // specified position. This is used to improve session consistency. Note that
355 // when LoadBalancer::waitFor() sets mWaitForPos, the waiting triggers here,
356 // so update laggedReplicaMode as needed for consistency.
357 if ( !$this->doWait( $i ) ) {
358 $laggedReplicaMode = true;
362 if ( $this->mReadIndex
<= 0 && $this->mLoads
[$i] > 0 && $group === false ) {
363 // Cache the generic reader index for future ungrouped DB_REPLICA handles
364 $this->mReadIndex
= $i;
365 // Record if the generic reader index is in "lagged replica DB" mode
366 if ( $laggedReplicaMode ) {
367 $this->laggedReplicaMode
= true;
371 $serverName = $this->getServerName( $i );
372 $this->connLogger
->debug( __METHOD__
. ": using server $serverName for group '$group'" );
378 * @param array $loads List of server weights
379 * @param string|bool $domain
380 * @return array (reader index, lagged replica mode) or false on failure
382 private function pickReaderIndex( array $loads, $domain = false ) {
383 if ( !count( $loads ) ) {
384 throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
387 /** @var $i int|bool Index of selected server */
389 /** @var $laggedReplicaMode bool Whether server is considered lagged */
390 $laggedReplicaMode = false;
392 // Quickly look through the available servers for a server that meets criteria...
393 $currentLoads = $loads;
394 while ( count( $currentLoads ) ) {
395 if ( $this->mAllowLagged ||
$laggedReplicaMode ) {
396 $i = ArrayUtils
::pickRandom( $currentLoads );
399 if ( $this->mWaitForPos
&& $this->mWaitForPos
->asOfTime() ) {
400 // ChronologyProtecter sets mWaitForPos for session consistency.
401 // This triggers doWait() after connect, so it's especially good to
402 // avoid lagged servers so as to avoid excessive delay in that method.
403 $ago = microtime( true ) - $this->mWaitForPos
->asOfTime();
404 // Aim for <= 1 second of waiting (being too picky can backfire)
405 $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago +
1 );
407 if ( $i === false ) {
408 // Any server with less lag than it's 'max lag' param is preferable
409 $i = $this->getRandomNonLagged( $currentLoads, $domain );
411 if ( $i === false && count( $currentLoads ) != 0 ) {
412 // All replica DBs lagged. Switch to read-only mode
413 $this->replLogger
->error( "All replica DBs lagged. Switch to read-only mode" );
414 $i = ArrayUtils
::pickRandom( $currentLoads );
415 $laggedReplicaMode = true;
419 if ( $i === false ) {
420 // pickRandom() returned false.
421 // This is permanent and means the configuration or the load monitor
422 // wants us to return false.
423 $this->connLogger
->debug( __METHOD__
. ": pickRandom() returned false" );
425 return [ false, false ];
428 $serverName = $this->getServerName( $i );
429 $this->connLogger
->debug( __METHOD__
. ": Using reader #$i: $serverName..." );
431 $conn = $this->openConnection( $i, $domain );
433 $this->connLogger
->warning( __METHOD__
. ": Failed connecting to $i/$domain" );
434 unset( $currentLoads[$i] ); // avoid this server next iteration
439 // Decrement reference counter, we are finished with this connection.
440 // It will be incremented for the caller later.
441 if ( $domain !== false ) {
442 $this->reuseConnection( $conn );
445 // Return this server
449 // If all servers were down, quit now
450 if ( !count( $currentLoads ) ) {
451 $this->connLogger
->error( "All servers down" );
454 return [ $i, $laggedReplicaMode ];
457 public function waitFor( $pos ) {
458 $oldPos = $this->mWaitForPos
;
460 $this->mWaitForPos
= $pos;
461 // If a generic reader connection was already established, then wait now
462 $i = $this->mReadIndex
;
464 if ( !$this->doWait( $i ) ) {
465 $this->laggedReplicaMode
= true;
469 // Restore the older position if it was higher since this is used for lag-protection
470 $this->setWaitForPositionIfHigher( $oldPos );
474 public function waitForOne( $pos, $timeout = null ) {
475 $oldPos = $this->mWaitForPos
;
477 $this->mWaitForPos
= $pos;
479 $i = $this->mReadIndex
;
481 // Pick a generic replica DB if there isn't one yet
482 $readLoads = $this->mLoads
;
483 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
484 $readLoads = array_filter( $readLoads ); // with non-zero load
485 $i = ArrayUtils
::pickRandom( $readLoads );
489 $ok = $this->doWait( $i, true, $timeout );
491 $ok = true; // no applicable loads
494 # Restore the old position, as this is not used for lag-protection but for throttling
495 $this->mWaitForPos
= $oldPos;
501 public function waitForAll( $pos, $timeout = null ) {
502 $oldPos = $this->mWaitForPos
;
504 $this->mWaitForPos
= $pos;
505 $serverCount = count( $this->mServers
);
508 for ( $i = 1; $i < $serverCount; $i++
) {
509 if ( $this->mLoads
[$i] > 0 ) {
510 $ok = $this->doWait( $i, true, $timeout ) && $ok;
514 # Restore the old position, as this is not used for lag-protection but for throttling
515 $this->mWaitForPos
= $oldPos;
522 * @param DBMasterPos|bool $pos
524 private function setWaitForPositionIfHigher( $pos ) {
529 if ( !$this->mWaitForPos ||
$pos->hasReached( $this->mWaitForPos
) ) {
530 $this->mWaitForPos
= $pos;
536 * @return IDatabase|bool
538 public function getAnyOpenConnection( $i ) {
539 foreach ( $this->mConns
as $connsByServer ) {
540 if ( !empty( $connsByServer[$i] ) ) {
541 /** @var $serverConns IDatabase[] */
542 $serverConns = $connsByServer[$i];
544 return reset( $serverConns );
552 * Wait for a given replica DB to catch up to the master pos stored in $this
553 * @param int $index Server index
554 * @param bool $open Check the server even if a new connection has to be made
555 * @param int $timeout Max seconds to wait; default is mWaitTimeout
558 protected function doWait( $index, $open = false, $timeout = null ) {
559 $close = false; // close the connection afterwards
561 // Check if we already know that the DB has reached this point
562 $server = $this->getServerName( $index );
563 $key = $this->srvCache
->makeGlobalKey( __CLASS__
, 'last-known-pos', $server, 'v1' );
564 /** @var DBMasterPos $knownReachedPos */
565 $knownReachedPos = $this->srvCache
->get( $key );
567 $knownReachedPos instanceof DBMasterPos
&&
568 $knownReachedPos->hasReached( $this->mWaitForPos
)
570 $this->replLogger
->debug( __METHOD__
.
571 ": replica DB $server known to be caught up (pos >= $knownReachedPos)." );
575 // Find a connection to wait on, creating one if needed and allowed
576 $conn = $this->getAnyOpenConnection( $index );
579 $this->replLogger
->debug( __METHOD__
. ": no connection open for $server" );
583 $conn = $this->openConnection( $index, self
::DOMAIN_ANY
);
585 $this->replLogger
->warning( __METHOD__
. ": failed to connect to $server" );
589 // Avoid connection spam in waitForAll() when connections
590 // are made just for the sake of doing this lag check.
595 $this->replLogger
->info( __METHOD__
. ": Waiting for replica DB $server to catch up..." );
596 $timeout = $timeout ?
: $this->mWaitTimeout
;
597 $result = $conn->masterPosWait( $this->mWaitForPos
, $timeout );
599 if ( $result == -1 ||
is_null( $result ) ) {
600 // Timed out waiting for replica DB, use master instead
601 $this->replLogger
->warning(
602 __METHOD__
. ": Timed out waiting on {host} pos {$this->mWaitForPos}",
603 [ 'host' => $server ]
607 $this->replLogger
->info( __METHOD__
. ": Done" );
609 // Remember that the DB reached this point
610 $this->srvCache
->set( $key, $this->mWaitForPos
, BagOStuff
::TTL_DAY
);
614 $this->closeConnection( $conn );
620 public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
621 if ( $i === null ||
$i === false ) {
622 throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__
.
623 ' with invalid server index' );
626 if ( $this->localDomain
->equals( $domain ) ||
$domain === $this->localDomainIdAlias
) {
627 $domain = false; // local connection requested
630 $groups = ( $groups === false ||
$groups === [] )
631 ?
[ false ] // check one "group": the generic pool
634 $masterOnly = ( $i == self
::DB_MASTER ||
$i == $this->getWriterIndex() );
635 $oldConnsOpened = $this->connsOpened
; // connections open now
637 if ( $i == self
::DB_MASTER
) {
638 $i = $this->getWriterIndex();
640 # Try to find an available server in any the query groups (in order)
641 foreach ( $groups as $group ) {
642 $groupIndex = $this->getReaderIndex( $group, $domain );
643 if ( $groupIndex !== false ) {
650 # Operation-based index
651 if ( $i == self
::DB_REPLICA
) {
652 $this->mLastError
= 'Unknown error'; // reset error string
653 # Try the general server pool if $groups are unavailable.
654 $i = ( $groups === [ false ] )
655 ?
false // don't bother with this if that is what was tried above
656 : $this->getReaderIndex( false, $domain );
657 # Couldn't find a working server in getReaderIndex()?
658 if ( $i === false ) {
659 $this->mLastError
= 'No working replica DB server: ' . $this->mLastError
;
660 // Throw an exception
661 $this->reportConnectionError();
662 return null; // not reached
666 # Now we have an explicit index into the servers array
667 $conn = $this->openConnection( $i, $domain, $flags );
669 // Throw an exception
670 $this->reportConnectionError();
671 return null; // not reached
674 # Profile any new connections that happen
675 if ( $this->connsOpened
> $oldConnsOpened ) {
676 $host = $conn->getServer();
677 $dbname = $conn->getDBname();
678 $this->trxProfiler
->recordConnection( $host, $dbname, $masterOnly );
682 # Make master-requested DB handles inherit any read-only mode setting
683 $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
689 public function reuseConnection( $conn ) {
690 $serverIndex = $conn->getLBInfo( 'serverIndex' );
691 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
692 if ( $serverIndex === null ||
$refCount === null ) {
694 * This can happen in code like:
695 * foreach ( $dbs as $db ) {
696 * $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
698 * $lb->reuseConnection( $conn );
700 * When a connection to the local DB is opened in this way, reuseConnection()
704 } elseif ( $conn instanceof DBConnRef
) {
705 // DBConnRef already handles calling reuseConnection() and only passes the live
706 // Database instance to this method. Any caller passing in a DBConnRef is broken.
707 $this->connLogger
->error( __METHOD__
. ": got DBConnRef instance.\n" .
708 ( new RuntimeException() )->getTraceAsString() );
713 if ( $this->disabled
) {
714 return; // DBConnRef handle probably survived longer than the LoadBalancer
717 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
718 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
719 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
721 $connFreeKey = self
::KEY_FOREIGN_FREE
;
722 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
725 $domain = $conn->getDomainID();
726 if ( !isset( $this->mConns
[$connInUseKey][$serverIndex][$domain] ) ) {
727 throw new InvalidArgumentException( __METHOD__
.
728 ": connection $serverIndex/$domain not found; it may have already been freed." );
729 } elseif ( $this->mConns
[$connInUseKey][$serverIndex][$domain] !== $conn ) {
730 throw new InvalidArgumentException( __METHOD__
.
731 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
734 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
735 if ( $refCount <= 0 ) {
736 $this->mConns
[$connFreeKey][$serverIndex][$domain] = $conn;
737 unset( $this->mConns
[$connInUseKey][$serverIndex][$domain] );
738 if ( !$this->mConns
[$connInUseKey][$serverIndex] ) {
739 unset( $this->mConns
[$connInUseKey][$serverIndex] ); // clean up
741 $this->connLogger
->debug( __METHOD__
. ": freed connection $serverIndex/$domain" );
743 $this->connLogger
->debug( __METHOD__
.
744 ": reference count for $serverIndex/$domain reduced to $refCount" );
748 public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
749 $domain = ( $domain !== false ) ?
$domain : $this->localDomain
;
751 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
754 public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
755 $domain = ( $domain !== false ) ?
$domain : $this->localDomain
;
757 return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
760 public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
761 $domain = ( $domain !== false ) ?
$domain : $this->localDomain
;
763 return new MaintainableDBConnRef(
764 $this, $this->getConnection( $db, $groups, $domain, $flags ) );
767 public function openConnection( $i, $domain = false, $flags = 0 ) {
768 if ( $this->localDomain
->equals( $domain ) ||
$domain === $this->localDomainIdAlias
) {
769 $domain = false; // local connection requested
772 if ( !$this->chronProtInitialized
&& $this->chronProt
) {
773 $this->connLogger
->debug( __METHOD__
. ': calling initLB() before first connection.' );
774 // Load CP positions before connecting so that doWait() triggers later if needed
775 $this->chronProtInitialized
= true;
776 $this->chronProt
->initLB( $this );
779 // Check if an auto-commit connection is being requested. If so, it will not reuse the
780 // main set of DB connections but rather its own pool since:
781 // a) those are usually set to implicitly use transaction rounds via DBO_TRX
782 // b) those must support the use of explicit transaction rounds via beginMasterChanges()
783 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTO
) == self
::CONN_TRX_AUTO
);
785 if ( $domain !== false ) {
786 // Connection is to a foreign domain
787 $conn = $this->openForeignConnection( $i, $domain, $flags );
789 // Connection is to the local domain
790 $connKey = $autoCommit ? self
::KEY_LOCAL_NOROUND
: self
::KEY_LOCAL
;
791 if ( isset( $this->mConns
[$connKey][$i][0] ) ) {
792 $conn = $this->mConns
[$connKey][$i][0];
794 if ( !isset( $this->mServers
[$i] ) ||
!is_array( $this->mServers
[$i] ) ) {
795 throw new InvalidArgumentException( "No server with index '$i'." );
797 // Open a new connection
798 $server = $this->mServers
[$i];
799 $server['serverIndex'] = $i;
800 $server['autoCommitOnly'] = $autoCommit;
801 $conn = $this->reallyOpenConnection( $server, false );
802 $host = $this->getServerName( $i );
803 if ( $conn->isOpen() ) {
804 $this->connLogger
->debug( "Connected to database $i at '$host'." );
805 $this->mConns
[$connKey][$i][0] = $conn;
807 $this->connLogger
->warning( "Failed to connect to database $i at '$host'." );
808 $this->errorConnection
= $conn;
814 if ( $conn instanceof IDatabase
&& !$conn->isOpen() ) {
815 // Connection was made but later unrecoverably lost for some reason.
816 // Do not return a handle that will just throw exceptions on use,
817 // but let the calling code (e.g. getReaderIndex) try another server.
818 // See DatabaseMyslBase::ping() for how this can happen.
819 $this->errorConnection
= $conn;
823 if ( $autoCommit && $conn instanceof IDatabase
) {
824 $conn->clearFlag( $conn::DBO_TRX
); // auto-commit mode
831 * Open a connection to a foreign DB, or return one if it is already open.
833 * Increments a reference count on the returned connection which locks the
834 * connection to the requested domain. This reference count can be
835 * decremented by calling reuseConnection().
837 * If a connection is open to the appropriate server already, but with the wrong
838 * database, it will be switched to the right database and returned, as long as
839 * it has been freed first with reuseConnection().
841 * On error, returns false, and the connection which caused the
842 * error will be available via $this->errorConnection.
844 * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
846 * @param int $i Server index
847 * @param string $domain Domain ID to open
848 * @param integer $flags Class CONN_* constant bitfield
851 private function openForeignConnection( $i, $domain, $flags = 0 ) {
852 $domainInstance = DatabaseDomain
::newFromId( $domain );
853 $dbName = $domainInstance->getDatabase();
854 $prefix = $domainInstance->getTablePrefix();
855 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTO
) == self
::CONN_TRX_AUTO
);
858 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
859 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
861 $connFreeKey = self
::KEY_FOREIGN_FREE
;
862 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
865 if ( isset( $this->mConns
[$connInUseKey][$i][$domain] ) ) {
866 // Reuse an in-use connection for the same domain
867 $conn = $this->mConns
[$connInUseKey][$i][$domain];
868 $this->connLogger
->debug( __METHOD__
. ": reusing connection $i/$domain" );
869 } elseif ( isset( $this->mConns
[$connFreeKey][$i][$domain] ) ) {
870 // Reuse a free connection for the same domain
871 $conn = $this->mConns
[$connFreeKey][$i][$domain];
872 unset( $this->mConns
[$connFreeKey][$i][$domain] );
873 $this->mConns
[$connInUseKey][$i][$domain] = $conn;
874 $this->connLogger
->debug( __METHOD__
. ": reusing free connection $i/$domain" );
875 } elseif ( !empty( $this->mConns
[$connFreeKey][$i] ) ) {
876 // Reuse a free connection from another domain
877 $conn = reset( $this->mConns
[$connFreeKey][$i] );
878 $oldDomain = key( $this->mConns
[$connFreeKey][$i] );
879 // The empty string as a DB name means "don't care".
880 // DatabaseMysqlBase::open() already handle this on connection.
881 if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
882 $this->mLastError
= "Error selecting database '$dbName' on server " .
883 $conn->getServer() . " from client host {$this->host}";
884 $this->errorConnection
= $conn;
887 $conn->tablePrefix( $prefix );
888 unset( $this->mConns
[$connFreeKey][$i][$oldDomain] );
889 $this->mConns
[$connInUseKey][$i][$domain] = $conn;
890 $this->connLogger
->debug( __METHOD__
.
891 ": reusing free connection from $oldDomain for $domain" );
894 if ( !isset( $this->mServers
[$i] ) ||
!is_array( $this->mServers
[$i] ) ) {
895 throw new InvalidArgumentException( "No server with index '$i'." );
897 // Open a new connection
898 $server = $this->mServers
[$i];
899 $server['serverIndex'] = $i;
900 $server['foreignPoolRefCount'] = 0;
901 $server['foreign'] = true;
902 $server['autoCommitOnly'] = $autoCommit;
903 $conn = $this->reallyOpenConnection( $server, $dbName );
904 if ( !$conn->isOpen() ) {
905 $this->connLogger
->warning( __METHOD__
. ": connection error for $i/$domain" );
906 $this->errorConnection
= $conn;
909 $conn->tablePrefix( $prefix );
910 $this->mConns
[$connInUseKey][$i][$domain] = $conn;
911 $this->connLogger
->debug( __METHOD__
. ": opened new connection for $i/$domain" );
915 // Increment reference count
916 if ( $conn instanceof IDatabase
) {
917 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
918 $conn->setLBInfo( 'foreignPoolRefCount', $refCount +
1 );
925 * Test if the specified index represents an open connection
927 * @param int $index Server index
931 private function isOpen( $index ) {
932 if ( !is_integer( $index ) ) {
936 return (bool)$this->getAnyOpenConnection( $index );
940 * Really opens a connection. Uncached.
941 * Returns a Database object whether or not the connection was successful.
944 * @param array $server
945 * @param string|bool $dbNameOverride Use "" to not select any database
947 * @throws DBAccessError
948 * @throws InvalidArgumentException
950 protected function reallyOpenConnection( array $server, $dbNameOverride = false ) {
951 if ( $this->disabled
) {
952 throw new DBAccessError();
955 if ( $dbNameOverride !== false ) {
956 $server['dbname'] = $dbNameOverride;
959 // Let the handle know what the cluster master is (e.g. "db1052")
960 $masterName = $this->getServerName( $this->getWriterIndex() );
961 $server['clusterMasterHost'] = $masterName;
963 // Log when many connection are made on requests
964 if ( ++
$this->connsOpened
>= self
::CONN_HELD_WARN_THRESHOLD
) {
965 $this->perfLogger
->warning( __METHOD__
. ": " .
966 "{$this->connsOpened}+ connections made (master=$masterName)" );
969 $server['srvCache'] = $this->srvCache
;
970 // Set loggers and profilers
971 $server['connLogger'] = $this->connLogger
;
972 $server['queryLogger'] = $this->queryLogger
;
973 $server['errorLogger'] = $this->errorLogger
;
974 $server['profiler'] = $this->profiler
;
975 $server['trxProfiler'] = $this->trxProfiler
;
976 // Use the same agent and PHP mode for all DB handles
977 $server['cliMode'] = $this->cliMode
;
978 $server['agent'] = $this->agent
;
979 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
980 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
981 $server['flags'] = isset( $server['flags'] ) ?
$server['flags'] : IDatabase
::DBO_DEFAULT
;
983 // Create a live connection object
985 $db = Database
::factory( $server['type'], $server );
986 } catch ( DBConnectionError
$e ) {
987 // FIXME: This is probably the ugliest thing I have ever done to
988 // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
992 $db->setLBInfo( $server );
993 $db->setLazyMasterHandle(
994 $this->getLazyConnectionRef( self
::DB_MASTER
, [], $db->getDomainID() )
996 $db->setTableAliases( $this->tableAliases
);
998 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
999 if ( $this->trxRoundId
!== false ) {
1000 $this->applyTransactionRoundFlags( $db );
1002 foreach ( $this->trxRecurringCallbacks
as $name => $callback ) {
1003 $db->setTransactionListener( $name, $callback );
1011 * @throws DBConnectionError
1013 private function reportConnectionError() {
1014 $conn = $this->errorConnection
; // the connection which caused the error
1016 'method' => __METHOD__
,
1017 'last_error' => $this->mLastError
,
1020 if ( $conn instanceof IDatabase
) {
1021 $context['db_server'] = $conn->getServer();
1022 $this->connLogger
->warning(
1023 "Connection error: {last_error} ({db_server})",
1027 // throws DBConnectionError
1028 $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
1030 // No last connection, probably due to all servers being too busy
1031 $this->connLogger
->error(
1032 "LB failure with no last connection. Connection error: {last_error}",
1036 // If all servers were busy, mLastError will contain something sensible
1037 throw new DBConnectionError( null, $this->mLastError
);
1041 public function getWriterIndex() {
1045 public function haveIndex( $i ) {
1046 return array_key_exists( $i, $this->mServers
);
1049 public function isNonZeroLoad( $i ) {
1050 return array_key_exists( $i, $this->mServers
) && $this->mLoads
[$i] != 0;
1053 public function getServerCount() {
1054 return count( $this->mServers
);
1057 public function getServerName( $i ) {
1058 if ( isset( $this->mServers
[$i]['hostName'] ) ) {
1059 $name = $this->mServers
[$i]['hostName'];
1060 } elseif ( isset( $this->mServers
[$i]['host'] ) ) {
1061 $name = $this->mServers
[$i]['host'];
1066 return ( $name != '' ) ?
$name : 'localhost';
1069 public function getServerType( $i ) {
1070 return isset( $this->mServers
[$i]['type'] ) ?
$this->mServers
[$i]['type'] : 'unknown';
1074 * @deprecated Since 1.30, no alternative
1076 public function getServerInfo( $i ) {
1077 wfDeprecated( __METHOD__
, '1.30' );
1078 if ( isset( $this->mServers
[$i] ) ) {
1079 return $this->mServers
[$i];
1086 * @deprecated Since 1.30, construct new object
1088 public function setServerInfo( $i, array $serverInfo ) {
1089 wfDeprecated( __METHOD__
, '1.30' );
1090 $this->mServers
[$i] = $serverInfo;
1093 public function getMasterPos() {
1094 # If this entire request was served from a replica DB without opening a connection to the
1095 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1096 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1097 if ( !$masterConn ) {
1098 $serverCount = count( $this->mServers
);
1099 for ( $i = 1; $i < $serverCount; $i++
) {
1100 $conn = $this->getAnyOpenConnection( $i );
1102 return $conn->getReplicaPos();
1106 return $masterConn->getMasterPos();
1112 public function disable() {
1114 $this->disabled
= true;
1117 public function closeAll() {
1118 $this->forEachOpenConnection( function ( IDatabase
$conn ) {
1119 $host = $conn->getServer();
1120 $this->connLogger
->debug( "Closing connection to database '$host'." );
1125 self
::KEY_LOCAL
=> [],
1126 self
::KEY_FOREIGN_INUSE
=> [],
1127 self
::KEY_FOREIGN_FREE
=> [],
1128 self
::KEY_LOCAL_NOROUND
=> [],
1129 self
::KEY_FOREIGN_INUSE_NOROUND
=> [],
1130 self
::KEY_FOREIGN_FREE_NOROUND
=> []
1132 $this->connsOpened
= 0;
1135 public function closeConnection( IDatabase
$conn ) {
1136 $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
1137 foreach ( $this->mConns
as $type => $connsByServer ) {
1138 if ( !isset( $connsByServer[$serverIndex] ) ) {
1142 foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1143 if ( $conn === $trackedConn ) {
1144 $host = $this->getServerName( $i );
1145 $this->connLogger
->debug( "Closing connection to database $i at '$host'." );
1146 unset( $this->mConns
[$type][$serverIndex][$i] );
1147 --$this->connsOpened
;
1156 public function commitAll( $fname = __METHOD__
) {
1159 $restore = ( $this->trxRoundId
!== false );
1160 $this->trxRoundId
= false;
1161 $this->forEachOpenConnection(
1162 function ( IDatabase
$conn ) use ( $fname, $restore, &$failures ) {
1164 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1165 } catch ( DBError
$e ) {
1166 call_user_func( $this->errorLogger
, $e );
1167 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1169 if ( $restore && $conn->getLBInfo( 'master' ) ) {
1170 $this->undoTransactionRoundFlags( $conn );
1176 throw new DBExpectedError(
1178 "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1183 public function finalizeMasterChanges() {
1184 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1185 // Any error should cause all DB transactions to be rolled back together
1186 $conn->setTrxEndCallbackSuppression( false );
1187 $conn->runOnTransactionPreCommitCallbacks();
1188 // Defer post-commit callbacks until COMMIT finishes for all DBs
1189 $conn->setTrxEndCallbackSuppression( true );
1193 public function approveMasterChanges( array $options ) {
1194 $limit = isset( $options['maxWriteDuration'] ) ?
$options['maxWriteDuration'] : 0;
1195 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $limit ) {
1196 // If atomic sections or explicit transactions are still open, some caller must have
1197 // caught an exception but failed to properly rollback any changes. Detect that and
1198 // throw and error (causing rollback).
1199 if ( $conn->explicitTrxActive() ) {
1200 throw new DBTransactionError(
1202 "Explicit transaction still active. A caller may have caught an error."
1205 // Assert that the time to replicate the transaction will be sane.
1206 // If this fails, then all DB transactions will be rollback back together.
1207 $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY
);
1208 if ( $limit > 0 && $time > $limit ) {
1209 throw new DBTransactionSizeError(
1211 "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
1215 // If a connection sits idle while slow queries execute on another, that connection
1216 // may end up dropped before the commit round is reached. Ping servers to detect this.
1217 if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1218 throw new DBTransactionError(
1220 "A connection to the {$conn->getDBname()} database was lost before commit."
1226 public function beginMasterChanges( $fname = __METHOD__
) {
1227 if ( $this->trxRoundId
!== false ) {
1228 throw new DBTransactionError(
1230 "$fname: Transaction round '{$this->trxRoundId}' already started."
1233 $this->trxRoundId
= $fname;
1236 $this->forEachOpenMasterConnection(
1237 function ( Database
$conn ) use ( $fname, &$failures ) {
1238 $conn->setTrxEndCallbackSuppression( true );
1240 $conn->flushSnapshot( $fname );
1241 } catch ( DBError
$e ) {
1242 call_user_func( $this->errorLogger
, $e );
1243 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1245 $conn->setTrxEndCallbackSuppression( false );
1246 $this->applyTransactionRoundFlags( $conn );
1251 throw new DBExpectedError(
1253 "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
1258 public function commitMasterChanges( $fname = __METHOD__
) {
1261 /** @noinspection PhpUnusedLocalVariableInspection */
1262 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1264 $restore = ( $this->trxRoundId
!== false );
1265 $this->trxRoundId
= false;
1266 $this->forEachOpenMasterConnection(
1267 function ( IDatabase
$conn ) use ( $fname, $restore, &$failures ) {
1269 if ( $conn->writesOrCallbacksPending() ) {
1270 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1271 } elseif ( $restore ) {
1272 $conn->flushSnapshot( $fname );
1274 } catch ( DBError
$e ) {
1275 call_user_func( $this->errorLogger
, $e );
1276 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1279 $this->undoTransactionRoundFlags( $conn );
1285 throw new DBExpectedError(
1287 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1292 public function runMasterPostTrxCallbacks( $type ) {
1293 $e = null; // first exception
1294 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( $type, &$e ) {
1295 $conn->setTrxEndCallbackSuppression( false );
1296 if ( $conn->writesOrCallbacksPending() ) {
1297 // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
1298 // (which finished its callbacks already). Warn and recover in this case. Let the
1299 // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
1300 $this->queryLogger
->info( __METHOD__
. ": found writes/callbacks pending." );
1302 } elseif ( $conn->trxLevel() ) {
1303 // This happens for single-DB setups where DB_REPLICA uses the master DB,
1304 // thus leaving an implicit read-only transaction open at this point. It
1305 // also happens if onTransactionIdle() callbacks leave implicit transactions
1306 // open on *other* DBs (which is slightly improper). Let these COMMIT on the
1307 // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
1311 $conn->runOnTransactionIdleCallbacks( $type );
1312 } catch ( Exception
$ex ) {
1316 $conn->runTransactionListenerCallbacks( $type );
1317 } catch ( Exception
$ex ) {
1325 public function rollbackMasterChanges( $fname = __METHOD__
) {
1326 $restore = ( $this->trxRoundId
!== false );
1327 $this->trxRoundId
= false;
1328 $this->forEachOpenMasterConnection(
1329 function ( IDatabase
$conn ) use ( $fname, $restore ) {
1330 if ( $conn->writesOrCallbacksPending() ) {
1331 $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS
);
1334 $this->undoTransactionRoundFlags( $conn );
1340 public function suppressTransactionEndCallbacks() {
1341 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1342 $conn->setTrxEndCallbackSuppression( true );
1347 * @param IDatabase $conn
1349 private function applyTransactionRoundFlags( IDatabase
$conn ) {
1350 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1351 return; // transaction rounds do not apply to these connections
1354 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1355 // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1356 // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1357 $conn->setFlag( $conn::DBO_TRX
, $conn::REMEMBER_PRIOR
);
1358 // If config has explicitly requested DBO_TRX be either on or off by not
1359 // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
1360 // for things like blob stores (ExternalStore) which want auto-commit mode.
1365 * @param IDatabase $conn
1367 private function undoTransactionRoundFlags( IDatabase
$conn ) {
1368 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1369 return; // transaction rounds do not apply to these connections
1372 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1373 $conn->restoreFlags( $conn::RESTORE_PRIOR
);
1377 public function flushReplicaSnapshots( $fname = __METHOD__
) {
1378 $this->forEachOpenReplicaConnection( function ( IDatabase
$conn ) {
1379 $conn->flushSnapshot( __METHOD__
);
1383 public function hasMasterConnection() {
1384 return $this->isOpen( $this->getWriterIndex() );
1387 public function hasMasterChanges() {
1389 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$pending ) {
1390 $pending |
= $conn->writesOrCallbacksPending();
1393 return (bool)$pending;
1396 public function lastMasterChangeTimestamp() {
1398 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$lastTime ) {
1399 $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1405 public function hasOrMadeRecentMasterChanges( $age = null ) {
1406 $age = ( $age === null ) ?
$this->mWaitTimeout
: $age;
1408 return ( $this->hasMasterChanges()
1409 ||
$this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1412 public function pendingMasterChangeCallers() {
1414 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$fnames ) {
1415 $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1421 public function getLaggedReplicaMode( $domain = false ) {
1422 // No-op if there is only one DB (also avoids recursion)
1423 if ( !$this->laggedReplicaMode
&& $this->getServerCount() > 1 ) {
1425 // See if laggedReplicaMode gets set
1426 $conn = $this->getConnection( self
::DB_REPLICA
, false, $domain );
1427 $this->reuseConnection( $conn );
1428 } catch ( DBConnectionError
$e ) {
1429 // Avoid expensive re-connect attempts and failures
1430 $this->allReplicasDownMode
= true;
1431 $this->laggedReplicaMode
= true;
1435 return $this->laggedReplicaMode
;
1439 * @param bool $domain
1441 * @deprecated 1.28; use getLaggedReplicaMode()
1443 public function getLaggedSlaveMode( $domain = false ) {
1444 return $this->getLaggedReplicaMode( $domain );
1447 public function laggedReplicaUsed() {
1448 return $this->laggedReplicaMode
;
1454 * @deprecated Since 1.28; use laggedReplicaUsed()
1456 public function laggedSlaveUsed() {
1457 return $this->laggedReplicaUsed();
1460 public function getReadOnlyReason( $domain = false, IDatabase
$conn = null ) {
1461 if ( $this->readOnlyReason
!== false ) {
1462 return $this->readOnlyReason
;
1463 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1464 if ( $this->allReplicasDownMode
) {
1465 return 'The database has been automatically locked ' .
1466 'until the replica database servers become available';
1468 return 'The database has been automatically locked ' .
1469 'while the replica database servers catch up to the master.';
1471 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1472 return 'The database master is running in read-only mode.';
1479 * @param string $domain Domain ID, or false for the current domain
1480 * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1483 private function masterRunningReadOnly( $domain, IDatabase
$conn = null ) {
1484 $cache = $this->wanCache
;
1485 $masterServer = $this->getServerName( $this->getWriterIndex() );
1487 return (bool)$cache->getWithSetCallback(
1488 $cache->makeGlobalKey( __CLASS__
, 'server-read-only', $masterServer ),
1489 self
::TTL_CACHE_READONLY
,
1490 function () use ( $domain, $conn ) {
1491 $old = $this->trxProfiler
->setSilenced( true );
1493 $dbw = $conn ?
: $this->getConnection( self
::DB_MASTER
, [], $domain );
1494 $readOnly = (int)$dbw->serverIsReadOnly();
1496 $this->reuseConnection( $dbw );
1498 } catch ( DBError
$e ) {
1501 $this->trxProfiler
->setSilenced( $old );
1504 [ 'pcTTL' => $cache::TTL_PROC_LONG
, 'busyValue' => 0 ]
1508 public function allowLagged( $mode = null ) {
1509 if ( $mode === null ) {
1510 return $this->mAllowLagged
;
1512 $this->mAllowLagged
= $mode;
1514 return $this->mAllowLagged
;
1517 public function pingAll() {
1519 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$success ) {
1520 if ( !$conn->ping() ) {
1528 public function forEachOpenConnection( $callback, array $params = [] ) {
1529 foreach ( $this->mConns
as $connsByServer ) {
1530 foreach ( $connsByServer as $serverConns ) {
1531 foreach ( $serverConns as $conn ) {
1532 $mergedParams = array_merge( [ $conn ], $params );
1533 call_user_func_array( $callback, $mergedParams );
1539 public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1540 $masterIndex = $this->getWriterIndex();
1541 foreach ( $this->mConns
as $connsByServer ) {
1542 if ( isset( $connsByServer[$masterIndex] ) ) {
1543 /** @var IDatabase $conn */
1544 foreach ( $connsByServer[$masterIndex] as $conn ) {
1545 $mergedParams = array_merge( [ $conn ], $params );
1546 call_user_func_array( $callback, $mergedParams );
1552 public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1553 foreach ( $this->mConns
as $connsByServer ) {
1554 foreach ( $connsByServer as $i => $serverConns ) {
1555 if ( $i === $this->getWriterIndex() ) {
1556 continue; // skip master
1558 foreach ( $serverConns as $conn ) {
1559 $mergedParams = array_merge( [ $conn ], $params );
1560 call_user_func_array( $callback, $mergedParams );
1566 public function getMaxLag( $domain = false ) {
1571 if ( $this->getServerCount() <= 1 ) {
1572 return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1575 $lagTimes = $this->getLagTimes( $domain );
1576 foreach ( $lagTimes as $i => $lag ) {
1577 if ( $this->mLoads
[$i] > 0 && $lag > $maxLag ) {
1579 $host = $this->mServers
[$i]['host'];
1584 return [ $host, $maxLag, $maxIndex ];
1587 public function getLagTimes( $domain = false ) {
1588 if ( $this->getServerCount() <= 1 ) {
1589 return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1592 $knownLagTimes = []; // map of (server index => 0 seconds)
1593 $indexesWithLag = [];
1594 foreach ( $this->mServers
as $i => $server ) {
1595 if ( empty( $server['is static'] ) ) {
1596 $indexesWithLag[] = $i; // DB server might have replication lag
1598 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1602 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) +
$knownLagTimes;
1605 public function safeGetLag( IDatabase
$conn ) {
1606 if ( $this->getServerCount() <= 1 ) {
1609 return $conn->getLag();
1614 * @param IDatabase $conn
1615 * @param DBMasterPos|bool $pos
1616 * @param int $timeout
1619 public function safeWaitForMasterPos( IDatabase
$conn, $pos = false, $timeout = 10 ) {
1620 if ( $this->getServerCount() <= 1 ||
!$conn->getLBInfo( 'replica' ) ) {
1621 return true; // server is not a replica DB
1625 // Get the current master position, opening a connection if needed
1626 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1627 if ( $masterConn ) {
1628 $pos = $masterConn->getMasterPos();
1630 $masterConn = $this->openConnection( $this->getWriterIndex(), self
::DOMAIN_ANY
);
1631 $pos = $masterConn->getMasterPos();
1632 $this->closeConnection( $masterConn );
1636 if ( $pos instanceof DBMasterPos
) {
1637 $result = $conn->masterPosWait( $pos, $timeout );
1638 if ( $result == -1 ||
is_null( $result ) ) {
1639 $msg = __METHOD__
. ": Timed out waiting on {$conn->getServer()} pos {$pos}";
1640 $this->replLogger
->warning( "$msg" );
1643 $this->replLogger
->info( __METHOD__
. ": Done" );
1647 $ok = false; // something is misconfigured
1648 $this->replLogger
->error( "Could not get master pos for {$conn->getServer()}." );
1654 public function setTransactionListener( $name, callable
$callback = null ) {
1656 $this->trxRecurringCallbacks
[$name] = $callback;
1658 unset( $this->trxRecurringCallbacks
[$name] );
1660 $this->forEachOpenMasterConnection(
1661 function ( IDatabase
$conn ) use ( $name, $callback ) {
1662 $conn->setTransactionListener( $name, $callback );
1667 public function setTableAliases( array $aliases ) {
1668 $this->tableAliases
= $aliases;
1671 public function setDomainPrefix( $prefix ) {
1672 // Find connections to explicit foreign domains still marked as in-use...
1674 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$domainsInUse ) {
1675 // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1676 // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1677 if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1678 $domainsInUse[] = $conn->getDomainID();
1682 // Do not switch connections to explicit foreign domains unless marked as safe
1683 if ( $domainsInUse ) {
1684 $domains = implode( ', ', $domainsInUse );
1685 throw new DBUnexpectedError( null,
1686 "Foreign domain connections are still in use ($domains)." );
1689 $this->localDomain
= new DatabaseDomain(
1690 $this->localDomain
->getDatabase(),
1695 $this->forEachOpenConnection( function ( IDatabase
$db ) use ( $prefix ) {
1696 $db->tablePrefix( $prefix );
1701 * Make PHP ignore user aborts/disconnects until the returned
1702 * value leaves scope. This returns null and does nothing in CLI mode.
1704 * @return ScopedCallback|null
1706 final protected function getScopedPHPBehaviorForCommit() {
1707 if ( PHP_SAPI
!= 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1708 $old = ignore_user_abort( true ); // avoid half-finished operations
1709 return new ScopedCallback( function () use ( $old ) {
1710 ignore_user_abort( $old );
1717 function __destruct() {
1718 // Avoid connection leaks for sanity
1723 class_alias( LoadBalancer
::class, 'LoadBalancer' );