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
22 namespace Wikimedia\Rdbms
;
24 use Psr\Log\LoggerInterface
;
25 use Psr\Log\NullLogger
;
26 use Wikimedia\ScopedCallback
;
32 use UnexpectedValueException
;
33 use InvalidArgumentException
;
38 * Database connection, tracking, load balancing, and transaction manager for a cluster
42 class LoadBalancer
implements ILoadBalancer
{
43 /** @var ILoadMonitor */
45 /** @var callable|null Callback to run before the first connection attempt */
46 private $chronologyCallback;
49 /** @var WANObjectCache */
51 /** @var mixed Class name or object With profileIn/profileOut methods */
53 /** @var TransactionProfiler */
55 /** @var LoggerInterface */
57 /** @var LoggerInterface */
59 /** @var LoggerInterface */
61 /** @var LoggerInterface */
63 /** @var callable Exception logger */
65 /** @var callable Deprecation logger */
66 private $deprecationLogger;
68 /** @var DatabaseDomain Local DB domain ID and default for selectDB() calls */
71 /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
74 /** @var array[] Map of (server index => server config array) */
76 /** @var array[] Map of (group => server index => weight) */
78 /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
80 /** @var int Seconds to spend waiting on replica DB lag to resolve */
82 /** @var array The LoadMonitor configuration */
83 private $loadMonitorConfig;
84 /** @var string Alternate local DB domain instead of DatabaseDomain::getId() */
85 private $localDomainIdAlias;
86 /** @var int Amount of replication lag, in seconds, that is considered "high" */
88 /** @var string|null Default query group to use with getConnection() */
89 private $defaultGroup;
91 /** @var string Current server name */
93 /** @var bool Whether this PHP instance is for a CLI script */
95 /** @var string Agent name for query profiling */
98 /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
99 private $tableAliases = [];
100 /** @var string[] Map of (index alias => index) */
101 private $indexAliases = [];
102 /** @var array[] Map of (name => callable) */
103 private $trxRecurringCallbacks = [];
104 /** @var bool[] Map of (domain => whether to use "temp tables only" mode) */
105 private $tempTablesOnlyMode = [];
107 /** @var Database Connection handle that caused a problem */
108 private $errorConnection;
109 /** @var int[] The group replica server indexes keyed by group */
110 private $readIndexByGroup = [];
111 /** @var bool|DBMasterPos Replication sync position or false if not set */
113 /** @var bool Whether the generic reader fell back to a lagged replica DB */
114 private $laggedReplicaMode = false;
115 /** @var string The last DB selection or connection error */
116 private $lastError = 'Unknown error';
117 /** @var string|bool Reason this instance is read-only or false if not */
118 private $readOnlyReason = false;
119 /** @var int Total number of new connections ever made with this instance */
120 private $connectionCounter = 0;
122 private $disabled = false;
123 /** @var bool Whether any connection has been attempted yet */
124 private $connectionAttempted = false;
126 /** @var int|null Integer ID of the managing LBFactory instance or null if none */
128 /** @var string|bool Explicit DBO_TRX transaction round active or false if none */
129 private $trxRoundId = false;
130 /** @var string Stage of the current transaction round in the transaction round life-cycle */
131 private $trxRoundStage = self
::ROUND_CURSORY
;
133 /** @var int Warn when this many connection are held */
134 const CONN_HELD_WARN_THRESHOLD
= 10;
136 /** @var int Default 'maxLag' when unspecified */
137 const MAX_LAG_DEFAULT
= 6;
138 /** @var int Default 'waitTimeout' when unspecified */
139 const MAX_WAIT_DEFAULT
= 10;
140 /** @var int Seconds to cache master DB server read-only status */
141 const TTL_CACHE_READONLY
= 5;
143 const KEY_LOCAL
= 'local';
144 const KEY_FOREIGN_FREE
= 'foreignFree';
145 const KEY_FOREIGN_INUSE
= 'foreignInUse';
147 const KEY_LOCAL_NOROUND
= 'localAutoCommit';
148 const KEY_FOREIGN_FREE_NOROUND
= 'foreignFreeAutoCommit';
149 const KEY_FOREIGN_INUSE_NOROUND
= 'foreignInUseAutoCommit';
151 /** @var string Transaction round, explicit or implicit, has not finished writing */
152 const ROUND_CURSORY
= 'cursory';
153 /** @var string Transaction round writes are complete and ready for pre-commit checks */
154 const ROUND_FINALIZED
= 'finalized';
155 /** @var string Transaction round passed final pre-commit checks */
156 const ROUND_APPROVED
= 'approved';
157 /** @var string Transaction round was committed and post-commit callbacks must be run */
158 const ROUND_COMMIT_CALLBACKS
= 'commit-callbacks';
159 /** @var string Transaction round was rolled back and post-rollback callbacks must be run */
160 const ROUND_ROLLBACK_CALLBACKS
= 'rollback-callbacks';
161 /** @var string Transaction round encountered an error */
162 const ROUND_ERROR
= 'error';
164 public function __construct( array $params ) {
165 if ( !isset( $params['servers'] ) ||
!count( $params['servers'] ) ) {
166 throw new InvalidArgumentException( 'Missing or empty "servers" parameter' );
171 $this->groupLoads
= [ self
::GROUP_GENERIC
=> [] ];
172 foreach ( $params['servers'] as $i => $server ) {
173 if ( ++
$listKey !== $i ) {
174 throw new UnexpectedValueException( 'List expected for "servers" parameter' );
177 $server['master'] = true;
179 $server['replica'] = true;
181 $this->servers
[$i] = $server;
182 foreach ( ( $server['groupLoads'] ??
[] ) as $group => $ratio ) {
183 $this->groupLoads
[$group][$i] = $ratio;
185 $this->groupLoads
[self
::GROUP_GENERIC
][$i] = $server['load'];
188 $localDomain = isset( $params['localDomain'] )
189 ? DatabaseDomain
::newFromId( $params['localDomain'] )
190 : DatabaseDomain
::newUnspecified();
191 $this->setLocalDomain( $localDomain );
193 $this->waitTimeout
= $params['waitTimeout'] ?? self
::MAX_WAIT_DEFAULT
;
195 $this->conns
= self
::newTrackedConnectionsArray();
196 $this->waitForPos
= false;
197 $this->allowLagged
= false;
199 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
200 $this->readOnlyReason
= $params['readOnlyReason'];
203 $this->maxLag
= $params['maxLag'] ?? self
::MAX_LAG_DEFAULT
;
205 $this->loadMonitorConfig
= $params['loadMonitor'] ??
[ 'class' => 'LoadMonitorNull' ];
206 $this->loadMonitorConfig +
= [ 'lagWarnThreshold' => $this->maxLag
];
208 $this->srvCache
= $params['srvCache'] ??
new EmptyBagOStuff();
209 $this->wanCache
= $params['wanCache'] ?? WANObjectCache
::newEmpty();
210 $this->profiler
= $params['profiler'] ??
null;
211 $this->trxProfiler
= $params['trxProfiler'] ??
new TransactionProfiler();
213 $this->errorLogger
= $params['errorLogger'] ??
function ( Exception
$e ) {
214 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING
);
216 $this->deprecationLogger
= $params['deprecationLogger'] ??
function ( $msg ) {
217 trigger_error( $msg, E_USER_DEPRECATED
);
220 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
221 $this->$key = $params[$key] ??
new NullLogger();
224 $this->hostname
= $params['hostname'] ??
( gethostname() ?
: 'unknown' );
225 $this->cliMode
= $params['cliMode'] ??
( PHP_SAPI
=== 'cli' || PHP_SAPI
=== 'phpdbg' );
226 $this->agent
= $params['agent'] ??
'';
228 if ( isset( $params['chronologyCallback'] ) ) {
229 $this->chronologyCallback
= $params['chronologyCallback'];
232 if ( isset( $params['roundStage'] ) ) {
233 if ( $params['roundStage'] === self
::STAGE_POSTCOMMIT_CALLBACKS
) {
234 $this->trxRoundStage
= self
::ROUND_COMMIT_CALLBACKS
;
235 } elseif ( $params['roundStage'] === self
::STAGE_POSTROLLBACK_CALLBACKS
) {
236 $this->trxRoundStage
= self
::ROUND_ROLLBACK_CALLBACKS
;
240 $group = $params['defaultGroup'] ?? self
::GROUP_GENERIC
;
241 $this->defaultGroup
= isset( $this->groupLoads
[$group] ) ?
$group : self
::GROUP_GENERIC
;
243 $this->ownerId
= $params['ownerId'] ??
null;
246 private static function newTrackedConnectionsArray() {
248 // Connection were transaction rounds may be applied
249 self
::KEY_LOCAL
=> [],
250 self
::KEY_FOREIGN_INUSE
=> [],
251 self
::KEY_FOREIGN_FREE
=> [],
252 // Auto-committing counterpart connections that ignore transaction rounds
253 self
::KEY_LOCAL_NOROUND
=> [],
254 self
::KEY_FOREIGN_INUSE_NOROUND
=> [],
255 self
::KEY_FOREIGN_FREE_NOROUND
=> []
259 public function getLocalDomainID() {
260 return $this->localDomain
->getId();
263 public function resolveDomainID( $domain ) {
264 if ( $domain === $this->localDomainIdAlias ||
$domain === false ) {
265 // Local connection requested via some backwards-compatibility domain alias
266 return $this->getLocalDomainID();
269 return (string)$domain;
273 * Resolve $groups into a list of query groups defining as having database servers
275 * @param string[]|string|bool $groups Query group(s) in preference order, [], or false
276 * @param int $i Specific server index or DB_MASTER/DB_REPLICA
277 * @return string[] Non-empty group list in preference order with the default group appended
279 private function resolveGroups( $groups, $i ) {
280 // If a specific replica server was specified, then $groups makes no sense
281 if ( $i > 0 && $groups !== [] && $groups !== false ) {
282 $list = implode( ', ', (array)$groups );
283 throw new LogicException( "Query group(s) ($list) given with server index (#$i)" );
286 if ( $groups === [] ||
$groups === false ||
$groups === $this->defaultGroup
) {
287 $resolvedGroups = [ $this->defaultGroup
]; // common case
288 } elseif ( is_string( $groups ) && isset( $this->groupLoads
[$groups] ) ) {
289 $resolvedGroups = [ $groups, $this->defaultGroup
];
290 } elseif ( is_array( $groups ) ) {
291 $resolvedGroups = array_keys( array_flip( $groups ) +
[ self
::GROUP_GENERIC
=> 1 ] );
293 $resolvedGroups = [ $this->defaultGroup
];
296 return $resolvedGroups;
300 * @param int $flags Bitfield of class CONN_* constants
301 * @param int $i Specific server index or DB_MASTER/DB_REPLICA
302 * @param string $domain Database domain
303 * @return int Sanitized bitfield
305 private function sanitizeConnectionFlags( $flags, $i, $domain ) {
306 // Whether an outside caller is explicitly requesting the master database server
307 if ( $i === self
::DB_MASTER ||
$i === $this->getWriterIndex() ) {
308 $flags |
= self
::CONN_INTENT_WRITABLE
;
311 if ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
) {
312 // Callers use CONN_TRX_AUTOCOMMIT to bypass REPEATABLE-READ staleness without
313 // resorting to row locks (e.g. FOR UPDATE) or to make small out-of-band commits
314 // during larger transactions. This is useful for avoiding lock contention.
316 // Master DB server attributes (should match those of the replica DB servers)
317 $attributes = $this->getServerAttributes( $this->getWriterIndex() );
318 if ( $attributes[Database
::ATTR_DB_LEVEL_LOCKING
] ) {
319 // The RDBMS does not support concurrent writes (e.g. SQLite), so attempts
320 // to use separate connections would just cause self-deadlocks. Note that
321 // REPEATABLE-READ staleness is not an issue since DB-level locking means
322 // that transactions are Strict Serializable anyway.
323 $flags &= ~self
::CONN_TRX_AUTOCOMMIT
;
324 $type = $this->getServerType( $this->getWriterIndex() );
325 $this->connLogger
->info( __METHOD__
. ": CONN_TRX_AUTOCOMMIT disallowed ($type)" );
326 } elseif ( isset( $this->tempTablesOnlyMode
[$domain] ) ) {
327 // T202116: integration tests are active and queries should be all be using
328 // temporary clone tables (via prefix). Such tables are not visible accross
329 // different connections nor can there be REPEATABLE-READ snapshot staleness,
330 // so use the same connection for everything.
331 $flags &= ~self
::CONN_TRX_AUTOCOMMIT
;
339 * @param IDatabase $conn
341 * @throws DBUnexpectedError
343 private function enforceConnectionFlags( IDatabase
$conn, $flags ) {
344 if ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
) {
345 if ( $conn->trxLevel() ) { // sanity
346 throw new DBUnexpectedError(
348 'Handle requested with CONN_TRX_AUTOCOMMIT yet it has a transaction'
352 $conn->clearFlag( $conn::DBO_TRX
); // auto-commit mode
357 * Get a LoadMonitor instance
359 * @return ILoadMonitor
361 private function getLoadMonitor() {
362 if ( !isset( $this->loadMonitor
) ) {
364 'LoadMonitor' => LoadMonitor
::class,
365 'LoadMonitorNull' => LoadMonitorNull
::class,
366 'LoadMonitorMySQL' => LoadMonitorMySQL
::class,
369 $class = $this->loadMonitorConfig
['class'];
370 if ( isset( $compat[$class] ) ) {
371 $class = $compat[$class];
374 $this->loadMonitor
= new $class(
375 $this, $this->srvCache
, $this->wanCache
, $this->loadMonitorConfig
);
376 $this->loadMonitor
->setLogger( $this->replLogger
);
379 return $this->loadMonitor
;
383 * @param array $loads
384 * @param bool|string $domain Domain to get non-lagged for
385 * @param int $maxLag Restrict the maximum allowed lag to this many seconds
386 * @return bool|int|string
388 private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF
) {
389 $lags = $this->getLagTimes( $domain );
391 # Unset excessively lagged servers
392 foreach ( $lags as $i => $lag ) {
393 if ( $i !== $this->getWriterIndex() ) {
394 # How much lag this server nominally is allowed to have
395 $maxServerLag = $this->servers
[$i]['max lag'] ??
$this->maxLag
; // default
396 # Constrain that futher by $maxLag argument
397 $maxServerLag = min( $maxServerLag, $maxLag );
399 $host = $this->getServerName( $i );
400 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
401 $this->replLogger
->debug(
403 ": server {host} is not replicating?", [ 'host' => $host ] );
405 } elseif ( $lag > $maxServerLag ) {
406 $this->replLogger
->debug(
408 ": server {host} has {lag} seconds of lag (>= {maxlag})",
409 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
416 # Find out if all the replica DBs with non-zero load are lagged
418 foreach ( $loads as $load ) {
422 # No appropriate DB servers except maybe the master and some replica DBs with zero load
423 # Do NOT use the master
424 # Instead, this function will return false, triggering read-only mode,
425 # and a lagged replica DB will be used instead.
429 if ( count( $loads ) == 0 ) {
433 # Return a random representative of the remainder
434 return ArrayUtils
::pickRandom( $loads );
438 * Get the server index to use for a specified server index and query group list
440 * @param int $i Specific server index or DB_MASTER/DB_REPLICA
441 * @param string[] $groups Non-empty query group list in preference order
442 * @param string|bool $domain
443 * @return int A specific server index (replica DBs are checked for connectivity)
445 private function getConnectionIndex( $i, array $groups, $domain ) {
446 if ( $i === self
::DB_MASTER
) {
447 $i = $this->getWriterIndex();
448 } elseif ( $i === self
::DB_REPLICA
) {
449 foreach ( $groups as $group ) {
450 $groupIndex = $this->getReaderIndex( $group, $domain );
451 if ( $groupIndex !== false ) {
452 $i = $groupIndex; // group connection succeeded
456 } elseif ( !isset( $this->servers
[$i] ) ) {
457 throw new UnexpectedValueException( "Invalid server index index #$i" );
460 if ( $i === self
::DB_REPLICA
) {
461 $this->lastError
= 'Unknown error'; // set here in case of worse failure
462 $this->lastError
= 'No working replica DB server: ' . $this->lastError
;
463 $this->reportConnectionError();
464 return null; // unreachable due to exception
470 public function getReaderIndex( $group = false, $domain = false ) {
471 if ( $this->getServerCount() == 1 ) {
472 // Skip the load balancing if there's only one server
473 return $this->getWriterIndex();
476 $group = is_string( $group ) ?
$group : self
::GROUP_GENERIC
;
478 $index = $this->getExistingReaderIndex( $group );
480 // A reader index was already selected and "waitForPos" was handled
484 // Use the server weight array for this load group
485 if ( isset( $this->groupLoads
[$group] ) ) {
486 $loads = $this->groupLoads
[$group];
488 $this->connLogger
->info( __METHOD__
. ": no loads for group $group" );
493 // Scale the configured load ratios according to each server's load and state
494 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
496 // Pick a server to use, accounting for weights, load, lag, and "waitForPos"
497 $this->lazyLoadReplicationPositions(); // optimizes server candidate selection
498 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
499 if ( $i === false ) {
500 // DB connection unsuccessful
504 // If data seen by queries is expected to reflect the transactions committed as of
505 // or after a given replication position then wait for the DB to apply those changes
506 if ( $this->waitForPos
&& $i !== $this->getWriterIndex() && !$this->doWait( $i ) ) {
507 // Data will be outdated compared to what was expected
508 $laggedReplicaMode = true;
511 // Cache the reader index for future DB_REPLICA handles
512 $this->setExistingReaderIndex( $group, $i );
513 // Record whether the generic reader index is in "lagged replica DB" mode
514 if ( $group === self
::GROUP_GENERIC
&& $laggedReplicaMode ) {
515 $this->laggedReplicaMode
= true;
518 $serverName = $this->getServerName( $i );
519 $this->connLogger
->debug( __METHOD__
. ": using server $serverName for group '$group'" );
525 * Get the server index chosen by the load balancer for use with the given query group
527 * @param string $group Query group; use false for the generic group
528 * @return int Server index or -1 if none was chosen
530 protected function getExistingReaderIndex( $group ) {
531 return $this->readIndexByGroup
[$group] ??
-1;
535 * Set the server index chosen by the load balancer for use with the given query group
537 * @param string $group Query group; use false for the generic group
538 * @param int $index The index of a specific server
540 private function setExistingReaderIndex( $group, $index ) {
542 throw new UnexpectedValueException( "Cannot set a negative read server index" );
544 $this->readIndexByGroup
[$group] = $index;
548 * @param array $loads List of server weights
549 * @param string|bool $domain
550 * @return array (reader index, lagged replica mode) or (false, false) on failure
552 private function pickReaderIndex( array $loads, $domain = false ) {
553 if ( $loads === [] ) {
554 throw new InvalidArgumentException( "Server configuration array is empty" );
557 /** @var int|bool $i Index of selected server */
559 /** @var bool $laggedReplicaMode Whether server is considered lagged */
560 $laggedReplicaMode = false;
562 // Quickly look through the available servers for a server that meets criteria...
563 $currentLoads = $loads;
564 while ( count( $currentLoads ) ) {
565 if ( $this->allowLagged ||
$laggedReplicaMode ) {
566 $i = ArrayUtils
::pickRandom( $currentLoads );
569 if ( $this->waitForPos
&& $this->waitForPos
->asOfTime() ) {
570 $this->replLogger
->debug( __METHOD__
. ": replication positions detected" );
571 // "chronologyCallback" sets "waitForPos" for session consistency.
572 // This triggers doWait() after connect, so it's especially good to
573 // avoid lagged servers so as to avoid excessive delay in that method.
574 $ago = microtime( true ) - $this->waitForPos
->asOfTime();
575 // Aim for <= 1 second of waiting (being too picky can backfire)
576 $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago +
1 );
578 if ( $i === false ) {
579 // Any server with less lag than it's 'max lag' param is preferable
580 $i = $this->getRandomNonLagged( $currentLoads, $domain );
582 if ( $i === false && count( $currentLoads ) ) {
583 // All replica DBs lagged. Switch to read-only mode
584 $this->replLogger
->error(
585 __METHOD__
. ": all replica DBs lagged. Switch to read-only mode" );
586 $i = ArrayUtils
::pickRandom( $currentLoads );
587 $laggedReplicaMode = true;
591 if ( $i === false ) {
592 // pickRandom() returned false.
593 // This is permanent and means the configuration or the load monitor
594 // wants us to return false.
595 $this->connLogger
->debug( __METHOD__
. ": pickRandom() returned false" );
597 return [ false, false ];
600 $serverName = $this->getServerName( $i );
601 $this->connLogger
->debug( __METHOD__
. ": Using reader #$i: $serverName..." );
603 // Get a connection to this server without triggering other server connections
604 $flags = self
::CONN_SILENCE_ERRORS
;
605 $conn = $this->getServerConnection( $i, $domain, $flags );
607 $this->connLogger
->warning( __METHOD__
. ": Failed connecting to $i/$domain" );
608 unset( $currentLoads[$i] ); // avoid this server next iteration
613 // Decrement reference counter, we are finished with this connection.
614 // It will be incremented for the caller later.
615 if ( $domain !== false ) {
616 $this->reuseConnection( $conn );
619 // Return this server
623 // If all servers were down, quit now
624 if ( $currentLoads === [] ) {
625 $this->connLogger
->error( __METHOD__
. ": all servers down" );
628 return [ $i, $laggedReplicaMode ];
631 public function waitFor( $pos ) {
632 $oldPos = $this->waitForPos
;
634 $this->waitForPos
= $pos;
635 // If a generic reader connection was already established, then wait now
636 $i = $this->getExistingReaderIndex( self
::GROUP_GENERIC
);
637 if ( $i > 0 && !$this->doWait( $i ) ) {
638 $this->laggedReplicaMode
= true;
640 // Otherwise, wait until a connection is established in getReaderIndex()
642 // Restore the older position if it was higher since this is used for lag-protection
643 $this->setWaitForPositionIfHigher( $oldPos );
647 public function waitForOne( $pos, $timeout = null ) {
648 $oldPos = $this->waitForPos
;
650 $this->waitForPos
= $pos;
652 $i = $this->getExistingReaderIndex( self
::GROUP_GENERIC
);
654 // Pick a generic replica DB if there isn't one yet
655 $readLoads = $this->groupLoads
[self
::GROUP_GENERIC
];
656 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
657 $readLoads = array_filter( $readLoads ); // with non-zero load
658 $i = ArrayUtils
::pickRandom( $readLoads );
662 $ok = $this->doWait( $i, true, $timeout );
664 $ok = true; // no applicable loads
667 // Restore the old position; this is used for throttling, not lag-protection
668 $this->waitForPos
= $oldPos;
674 public function waitForAll( $pos, $timeout = null ) {
675 $timeout = $timeout ?
: $this->waitTimeout
;
677 $oldPos = $this->waitForPos
;
679 $this->waitForPos
= $pos;
680 $serverCount = $this->getServerCount();
683 for ( $i = 1; $i < $serverCount; $i++
) {
684 if ( $this->serverHasLoadInAnyGroup( $i ) ) {
685 $start = microtime( true );
686 $ok = $this->doWait( $i, true, $timeout ) && $ok;
687 $timeout -= intval( microtime( true ) - $start );
688 if ( $timeout <= 0 ) {
689 break; // timeout reached
694 // Restore the old position; this is used for throttling, not lag-protection
695 $this->waitForPos
= $oldPos;
702 * @param int $i Specific server index
705 private function serverHasLoadInAnyGroup( $i ) {
706 foreach ( $this->groupLoads
as $loadsByIndex ) {
707 if ( ( $loadsByIndex[$i] ??
0 ) > 0 ) {
716 * @param DBMasterPos|bool $pos
718 private function setWaitForPositionIfHigher( $pos ) {
723 if ( !$this->waitForPos ||
$pos->hasReached( $this->waitForPos
) ) {
724 $this->waitForPos
= $pos;
728 public function getAnyOpenConnection( $i, $flags = 0 ) {
729 $i = ( $i === self
::DB_MASTER
) ?
$this->getWriterIndex() : $i;
730 // Connection handles required to be in auto-commit mode use a separate connection
731 // pool since the main pool is effected by implicit and explicit transaction rounds
732 $autocommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
735 foreach ( $this->conns
as $connsByServer ) {
736 // Get the connection array server indexes to inspect
737 if ( $i === self
::DB_REPLICA
) {
738 $indexes = array_keys( $connsByServer );
740 $indexes = isset( $connsByServer[$i] ) ?
[ $i ] : [];
743 foreach ( $indexes as $index ) {
744 $conn = $this->pickAnyOpenConnection( $connsByServer[$index], $autocommit );
752 $this->enforceConnectionFlags( $conn, $flags );
759 * @param IDatabase[] $candidateConns
760 * @param bool $autocommit Whether to only look for auto-commit connections
761 * @return IDatabase|false An appropriate open connection or false if none found
763 private function pickAnyOpenConnection( $candidateConns, $autocommit ) {
766 foreach ( $candidateConns as $candidateConn ) {
767 if ( !$candidateConn->isOpen() ) {
768 continue; // some sort of error occured?
772 // Connection is transaction round aware
773 !$candidateConn->getLBInfo( 'autoCommitOnly' ) ||
774 // Some sort of error left a transaction open?
775 $candidateConn->trxLevel()
778 continue; // some sort of error left a transaction open?
781 $conn = $candidateConn;
788 * Wait for a given replica DB to catch up to the master pos stored in "waitForPos"
789 * @param int $index Specific server index
790 * @param bool $open Check the server even if a new connection has to be made
791 * @param int|null $timeout Max seconds to wait; default is "waitTimeout"
794 protected function doWait( $index, $open = false, $timeout = null ) {
795 $timeout = max( 1, intval( $timeout ?
: $this->waitTimeout
) );
797 // Check if we already know that the DB has reached this point
798 $server = $this->getServerName( $index );
799 $key = $this->srvCache
->makeGlobalKey( __CLASS__
, 'last-known-pos', $server, 'v1' );
800 /** @var DBMasterPos $knownReachedPos */
801 $knownReachedPos = $this->srvCache
->get( $key );
803 $knownReachedPos instanceof DBMasterPos
&&
804 $knownReachedPos->hasReached( $this->waitForPos
)
806 $this->replLogger
->debug(
808 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
809 [ 'dbserver' => $server ]
814 // Find a connection to wait on, creating one if needed and allowed
815 $close = false; // close the connection afterwards
816 $flags = self
::CONN_SILENCE_ERRORS
;
817 $conn = $this->getAnyOpenConnection( $index, $flags );
820 $this->replLogger
->debug(
821 __METHOD__
. ': no connection open for {dbserver}',
822 [ 'dbserver' => $server ]
827 // Get a connection to this server without triggering other server connections
828 $conn = $this->getServerConnection( $index, self
::DOMAIN_ANY
, $flags );
830 $this->replLogger
->warning(
831 __METHOD__
. ': failed to connect to {dbserver}',
832 [ 'dbserver' => $server ]
837 // Avoid connection spam in waitForAll() when connections
838 // are made just for the sake of doing this lag check.
842 $this->replLogger
->info(
844 ': waiting for replica DB {dbserver} to catch up...',
845 [ 'dbserver' => $server ]
848 $result = $conn->masterPosWait( $this->waitForPos
, $timeout );
850 if ( $result === null ) {
851 $this->replLogger
->warning(
852 __METHOD__
. ': Errored out waiting on {host} pos {pos}',
855 'pos' => $this->waitForPos
,
856 'trace' => ( new RuntimeException() )->getTraceAsString()
860 } elseif ( $result == -1 ) {
861 $this->replLogger
->warning(
862 __METHOD__
. ': Timed out waiting on {host} pos {pos}',
865 'pos' => $this->waitForPos
,
866 'trace' => ( new RuntimeException() )->getTraceAsString()
871 $this->replLogger
->debug( __METHOD__
. ": done waiting" );
873 // Remember that the DB reached this point
874 $this->srvCache
->set( $key, $this->waitForPos
, BagOStuff
::TTL_DAY
);
878 $this->closeConnection( $conn );
884 public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
885 $domain = $this->resolveDomainID( $domain );
886 $groups = $this->resolveGroups( $groups, $i );
887 $flags = $this->sanitizeConnectionFlags( $flags, $i, $domain );
888 // If given DB_MASTER/DB_REPLICA, resolve it to a specific server index. Resolving
889 // DB_REPLICA might trigger getServerConnection() calls due to the getReaderIndex()
890 // connectivity checks or LoadMonitor::scaleLoads() server state cache regeneration.
891 // The use of getServerConnection() instead of getConnection() avoids infinite loops.
892 $serverIndex = $this->getConnectionIndex( $i, $groups, $domain );
893 // Get an open connection to that server (might trigger a new connection)
894 $conn = $this->getServerConnection( $serverIndex, $domain, $flags );
895 // Set master DB handles as read-only if there is high replication lag
896 if ( $serverIndex === $this->getWriterIndex() && $this->getLaggedReplicaMode( $domain ) ) {
897 $reason = ( $this->getExistingReaderIndex( self
::GROUP_GENERIC
) >= 0 )
898 ?
'The database is read-only until replication lag decreases.'
899 : 'The database is read-only until replica database servers becomes reachable.';
900 $conn->setLBInfo( 'readOnlyReason', $reason );
907 * @param int $i Specific server index
908 * @param string $domain Resolved DB domain
909 * @param int $flags Bitfield of class CONN_* constants
910 * @return IDatabase|bool
911 * @throws InvalidArgumentException When the server index is invalid
913 public function getServerConnection( $i, $domain, $flags = 0 ) {
914 // Number of connections made before getting the server index and handle
915 $priorConnectionsMade = $this->connectionCounter
;
916 // Get an open connection to this server (might trigger a new connection)
917 $conn = $this->localDomain
->equals( $domain )
918 ?
$this->getLocalConnection( $i, $flags )
919 : $this->getForeignConnection( $i, $domain, $flags );
920 // Throw an error or otherwise bail out if the connection attempt failed
921 if ( !( $conn instanceof IDatabase
) ) {
922 if ( ( $flags & self
::CONN_SILENCE_ERRORS
) != self
::CONN_SILENCE_ERRORS
) {
923 $this->reportConnectionError();
929 // Profile any new connections caused by this method
930 if ( $this->connectionCounter
> $priorConnectionsMade ) {
931 $this->trxProfiler
->recordConnection(
934 ( ( $flags & self
::CONN_INTENT_WRITABLE
) == self
::CONN_INTENT_WRITABLE
)
938 if ( !$conn->isOpen() ) {
939 $this->errorConnection
= $conn;
940 // Connection was made but later unrecoverably lost for some reason.
941 // Do not return a handle that will just throw exceptions on use, but
942 // let the calling code, e.g. getReaderIndex(), try another server.
946 // Make sure that flags like CONN_TRX_AUTOCOMMIT are respected by this handle
947 $this->enforceConnectionFlags( $conn, $flags );
948 // Set master DB handles as read-only if the load balancer is configured as read-only
949 // or the master database server is running in server-side read-only mode. Note that
950 // replica DB handles are always read-only via Database::assertIsWritableMaster().
951 // Read-only mode due to replication lag is *avoided* here to avoid recursion.
952 if ( $conn->getLBInfo( 'serverIndex' ) === $this->getWriterIndex() ) {
953 if ( $this->readOnlyReason
!== false ) {
954 $conn->setLBInfo( 'readOnlyReason', $this->readOnlyReason
);
955 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
958 'The master database server is running in read-only mode.'
966 public function reuseConnection( IDatabase
$conn ) {
967 $serverIndex = $conn->getLBInfo( 'serverIndex' );
968 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
969 if ( $serverIndex === null ||
$refCount === null ) {
971 * This can happen in code like:
972 * foreach ( $dbs as $db ) {
973 * $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
975 * $lb->reuseConnection( $conn );
977 * When a connection to the local DB is opened in this way, reuseConnection()
981 } elseif ( $conn instanceof DBConnRef
) {
982 // DBConnRef already handles calling reuseConnection() and only passes the live
983 // Database instance to this method. Any caller passing in a DBConnRef is broken.
984 $this->connLogger
->error(
985 __METHOD__
. ": got DBConnRef instance.\n" .
986 ( new LogicException() )->getTraceAsString() );
991 if ( $this->disabled
) {
992 return; // DBConnRef handle probably survived longer than the LoadBalancer
995 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
996 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
997 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
999 $connFreeKey = self
::KEY_FOREIGN_FREE
;
1000 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
1003 $domain = $conn->getDomainID();
1004 if ( !isset( $this->conns
[$connInUseKey][$serverIndex][$domain] ) ) {
1005 throw new InvalidArgumentException(
1006 "Connection $serverIndex/$domain not found; it may have already been freed" );
1007 } elseif ( $this->conns
[$connInUseKey][$serverIndex][$domain] !== $conn ) {
1008 throw new InvalidArgumentException(
1009 "Connection $serverIndex/$domain mismatched; it may have already been freed" );
1012 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
1013 if ( $refCount <= 0 ) {
1014 $this->conns
[$connFreeKey][$serverIndex][$domain] = $conn;
1015 unset( $this->conns
[$connInUseKey][$serverIndex][$domain] );
1016 if ( !$this->conns
[$connInUseKey][$serverIndex] ) {
1017 unset( $this->conns
[$connInUseKey][$serverIndex] ); // clean up
1019 $this->connLogger
->debug( __METHOD__
. ": freed connection $serverIndex/$domain" );
1021 $this->connLogger
->debug( __METHOD__
.
1022 ": reference count for $serverIndex/$domain reduced to $refCount" );
1026 public function getConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
1027 $domain = $this->resolveDomainID( $domain );
1028 $role = $this->getRoleFromIndex( $i );
1030 return new DBConnRef( $this, $this->getConnection( $i, $groups, $domain, $flags ), $role );
1033 public function getLazyConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
1034 $domain = $this->resolveDomainID( $domain );
1035 $role = $this->getRoleFromIndex( $i );
1037 return new DBConnRef( $this, [ $i, $groups, $domain, $flags ], $role );
1040 public function getMaintenanceConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
1041 $domain = $this->resolveDomainID( $domain );
1042 $role = $this->getRoleFromIndex( $i );
1044 return new MaintainableDBConnRef(
1045 $this, $this->getConnection( $i, $groups, $domain, $flags ), $role );
1049 * @param int $i Server index or DB_MASTER/DB_REPLICA
1050 * @return int One of DB_MASTER/DB_REPLICA
1052 private function getRoleFromIndex( $i ) {
1053 return ( $i === self
::DB_MASTER ||
$i === $this->getWriterIndex() )
1060 * @param string|bool $domain
1062 * @return Database|bool Live database handle or false on failure
1063 * @deprecated Since 1.34 Use getConnection() instead
1065 public function openConnection( $i, $domain = false, $flags = 0 ) {
1066 return $this->getConnection( $i, [], $domain, $flags | self
::CONN_SILENCE_ERRORS
);
1070 * Open a connection to a local DB, or return one if it is already open.
1072 * On error, returns false, and the connection which caused the
1073 * error will be available via $this->errorConnection.
1075 * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
1077 * @param int $i Server index
1078 * @param int $flags Class CONN_* constant bitfield
1080 * @throws InvalidArgumentException When the server index is invalid
1081 * @throws UnexpectedValueException When the DB domain of the connection is corrupted
1083 private function getLocalConnection( $i, $flags = 0 ) {
1084 // Connection handles required to be in auto-commit mode use a separate connection
1085 // pool since the main pool is effected by implicit and explicit transaction rounds
1086 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
1088 $connKey = $autoCommit ? self
::KEY_LOCAL_NOROUND
: self
::KEY_LOCAL
;
1089 if ( isset( $this->conns
[$connKey][$i][0] ) ) {
1090 $conn = $this->conns
[$connKey][$i][0];
1092 // Open a new connection
1093 $server = $this->getServerInfoStrict( $i );
1094 $server['serverIndex'] = $i;
1095 $server['autoCommitOnly'] = $autoCommit;
1096 $conn = $this->reallyOpenConnection( $server, $this->localDomain
);
1097 $host = $this->getServerName( $i );
1098 if ( $conn->isOpen() ) {
1099 $this->connLogger
->debug(
1100 __METHOD__
. ": connected to database $i at '$host'." );
1101 $this->conns
[$connKey][$i][0] = $conn;
1103 $this->connLogger
->warning(
1104 __METHOD__
. ": failed to connect to database $i at '$host'." );
1105 $this->errorConnection
= $conn;
1110 // Final sanity check to make sure the right domain is selected
1112 $conn instanceof IDatabase
&&
1113 !$this->localDomain
->isCompatible( $conn->getDomainID() )
1115 throw new UnexpectedValueException(
1116 "Got connection to '{$conn->getDomainID()}', " .
1117 "but expected local domain ('{$this->localDomain}')" );
1124 * Open a connection to a foreign DB, or return one if it is already open.
1126 * Increments a reference count on the returned connection which locks the
1127 * connection to the requested domain. This reference count can be
1128 * decremented by calling reuseConnection().
1130 * If a connection is open to the appropriate server already, but with the wrong
1131 * database, it will be switched to the right database and returned, as long as
1132 * it has been freed first with reuseConnection().
1134 * On error, returns false, and the connection which caused the
1135 * error will be available via $this->errorConnection.
1137 * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
1139 * @param int $i Server index
1140 * @param string $domain Domain ID to open
1141 * @param int $flags Class CONN_* constant bitfield
1142 * @return Database|bool Returns false on connection error
1143 * @throws DBError When database selection fails
1144 * @throws InvalidArgumentException When the server index is invalid
1145 * @throws UnexpectedValueException When the DB domain of the connection is corrupted
1147 private function getForeignConnection( $i, $domain, $flags = 0 ) {
1148 $domainInstance = DatabaseDomain
::newFromId( $domain );
1149 // Connection handles required to be in auto-commit mode use a separate connection
1150 // pool since the main pool is effected by implicit and explicit transaction rounds
1151 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
1153 if ( $autoCommit ) {
1154 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
1155 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
1157 $connFreeKey = self
::KEY_FOREIGN_FREE
;
1158 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
1161 /** @var Database $conn */
1164 if ( isset( $this->conns
[$connInUseKey][$i][$domain] ) ) {
1165 // Reuse an in-use connection for the same domain
1166 $conn = $this->conns
[$connInUseKey][$i][$domain];
1167 $this->connLogger
->debug( __METHOD__
. ": reusing connection $i/$domain" );
1168 } elseif ( isset( $this->conns
[$connFreeKey][$i][$domain] ) ) {
1169 // Reuse a free connection for the same domain
1170 $conn = $this->conns
[$connFreeKey][$i][$domain];
1171 unset( $this->conns
[$connFreeKey][$i][$domain] );
1172 $this->conns
[$connInUseKey][$i][$domain] = $conn;
1173 $this->connLogger
->debug( __METHOD__
. ": reusing free connection $i/$domain" );
1174 } elseif ( !empty( $this->conns
[$connFreeKey][$i] ) ) {
1175 // Reuse a free connection from another domain if possible
1176 foreach ( $this->conns
[$connFreeKey][$i] as $oldDomain => $conn ) {
1177 if ( $domainInstance->getDatabase() !== null ) {
1178 // Check if changing the database will require a new connection.
1179 // In that case, leave the connection handle alone and keep looking.
1180 // This prevents connections from being closed mid-transaction and can
1181 // also avoid overhead if the same database will later be requested.
1183 $conn->databasesAreIndependent() &&
1184 $conn->getDBname() !== $domainInstance->getDatabase()
1188 // Select the new database, schema, and prefix
1189 $conn->selectDomain( $domainInstance );
1191 // Stay on the current database, but update the schema/prefix
1192 $conn->dbSchema( $domainInstance->getSchema() );
1193 $conn->tablePrefix( $domainInstance->getTablePrefix() );
1195 unset( $this->conns
[$connFreeKey][$i][$oldDomain] );
1196 // Note that if $domain is an empty string, getDomainID() might not match it
1197 $this->conns
[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1198 $this->connLogger
->debug( __METHOD__
.
1199 ": reusing free connection from $oldDomain for $domain" );
1205 // Open a new connection
1206 $server = $this->getServerInfoStrict( $i );
1207 $server['serverIndex'] = $i;
1208 $server['foreignPoolRefCount'] = 0;
1209 $server['foreign'] = true;
1210 $server['autoCommitOnly'] = $autoCommit;
1211 $conn = $this->reallyOpenConnection( $server, $domainInstance );
1212 if ( !$conn->isOpen() ) {
1213 $this->connLogger
->warning( __METHOD__
. ": connection error for $i/$domain" );
1214 $this->errorConnection
= $conn;
1217 // Note that if $domain is an empty string, getDomainID() might not match it
1218 $this->conns
[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1219 $this->connLogger
->debug( __METHOD__
. ": opened new connection for $i/$domain" );
1223 if ( $conn instanceof IDatabase
) {
1224 // Final sanity check to make sure the right domain is selected
1225 if ( !$domainInstance->isCompatible( $conn->getDomainID() ) ) {
1226 throw new UnexpectedValueException(
1227 "Got connection to '{$conn->getDomainID()}', but expected '$domain'" );
1229 // Increment reference count
1230 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
1231 $conn->setLBInfo( 'foreignPoolRefCount', $refCount +
1 );
1237 public function getServerAttributes( $i ) {
1238 return Database
::attributesFromType(
1239 $this->getServerType( $i ),
1240 $this->servers
[$i]['driver'] ??
null
1245 * Test if the specified index represents an open connection
1247 * @param int $index Server index
1250 private function isOpen( $index ) {
1251 return (bool)$this->getAnyOpenConnection( $index );
1255 * Open a new network connection to a server (uncached)
1257 * Returns a Database object whether or not the connection was successful.
1259 * @param array $server
1260 * @param DatabaseDomain $domain Domain the connection is for, possibly unspecified
1262 * @throws DBAccessError
1263 * @throws InvalidArgumentException
1265 protected function reallyOpenConnection( array $server, DatabaseDomain
$domain ) {
1266 if ( $this->disabled
) {
1267 throw new DBAccessError();
1270 if ( $domain->getDatabase() === null ) {
1271 // The database domain does not specify a DB name and some database systems require a
1272 // valid DB specified on connection. The $server configuration array contains a default
1273 // DB name to use for connections in such cases.
1274 if ( $server['type'] === 'mysql' ) {
1275 // For MySQL, DATABASE and SCHEMA are synonyms, connections need not specify a DB,
1276 // and the DB name in $server might not exist due to legacy reasons (the default
1277 // domain used to ignore the local LB domain, even when mismatched).
1278 $server['dbname'] = null;
1281 $server['dbname'] = $domain->getDatabase();
1284 if ( $domain->getSchema() !== null ) {
1285 $server['schema'] = $domain->getSchema();
1288 // It is always possible to connect with any prefix, even the empty string
1289 $server['tablePrefix'] = $domain->getTablePrefix();
1291 // Let the handle know what the cluster master is (e.g. "db1052")
1292 $masterName = $this->getServerName( $this->getWriterIndex() );
1293 $server['clusterMasterHost'] = $masterName;
1295 $server['srvCache'] = $this->srvCache
;
1296 // Set loggers and profilers
1297 $server['connLogger'] = $this->connLogger
;
1298 $server['queryLogger'] = $this->queryLogger
;
1299 $server['errorLogger'] = $this->errorLogger
;
1300 $server['deprecationLogger'] = $this->deprecationLogger
;
1301 $server['profiler'] = $this->profiler
;
1302 $server['trxProfiler'] = $this->trxProfiler
;
1303 // Use the same agent and PHP mode for all DB handles
1304 $server['cliMode'] = $this->cliMode
;
1305 $server['agent'] = $this->agent
;
1306 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
1307 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
1308 $server['flags'] = $server['flags'] ?? IDatabase
::DBO_DEFAULT
;
1310 // Create a live connection object
1312 $db = Database
::factory( $server['type'], $server );
1313 // Log when many connection are made on requests
1314 ++
$this->connectionCounter
;
1315 $currentConnCount = $this->getCurrentConnectionCount();
1316 if ( $currentConnCount >= self
::CONN_HELD_WARN_THRESHOLD
) {
1317 $this->perfLogger
->warning(
1318 __METHOD__
. ": {connections}+ connections made (master={masterdb})",
1319 [ 'connections' => $currentConnCount, 'masterdb' => $masterName ]
1322 } catch ( DBConnectionError
$e ) {
1323 // FIXME: This is probably the ugliest thing I have ever done to
1324 // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
1328 $db->setLBInfo( $server );
1329 $db->setLazyMasterHandle(
1330 $this->getLazyConnectionRef( self
::DB_MASTER
, [], $db->getDomainID() )
1332 $db->setTableAliases( $this->tableAliases
);
1333 $db->setIndexAliases( $this->indexAliases
);
1335 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1336 if ( $this->trxRoundId
!== false ) {
1337 $this->applyTransactionRoundFlags( $db );
1339 foreach ( $this->trxRecurringCallbacks
as $name => $callback ) {
1340 $db->setTransactionListener( $name, $callback );
1344 $this->lazyLoadReplicationPositions(); // session consistency
1350 * Make sure that any "waitForPos" positions are loaded and available to doWait()
1352 private function lazyLoadReplicationPositions() {
1353 if ( !$this->connectionAttempted
&& $this->chronologyCallback
) {
1354 $this->connectionAttempted
= true;
1355 ( $this->chronologyCallback
)( $this ); // generally calls waitFor()
1356 $this->connLogger
->debug( __METHOD__
. ': executed chronology callback.' );
1361 * @throws DBConnectionError
1363 private function reportConnectionError() {
1364 $conn = $this->errorConnection
; // the connection which caused the error
1366 'method' => __METHOD__
,
1367 'last_error' => $this->lastError
,
1370 if ( $conn instanceof IDatabase
) {
1371 $context['db_server'] = $conn->getServer();
1372 $this->connLogger
->warning(
1373 __METHOD__
. ": connection error: {last_error} ({db_server})",
1377 throw new DBConnectionError( $conn, "{$this->lastError} ({$context['db_server']})" );
1379 // No last connection, probably due to all servers being too busy
1380 $this->connLogger
->error(
1382 ": LB failure with no last connection. Connection error: {last_error}",
1386 // If all servers were busy, "lastError" will contain something sensible
1387 throw new DBConnectionError( null, $this->lastError
);
1391 public function getWriterIndex() {
1396 * Returns true if the specified index is a valid server index
1400 * @deprecated Since 1.34
1402 public function haveIndex( $i ) {
1403 return array_key_exists( $i, $this->servers
);
1407 * Returns true if the specified index is valid and has non-zero load
1411 * @deprecated Since 1.34
1413 public function isNonZeroLoad( $i ) {
1414 return ( isset( $this->servers
[$i] ) && $this->groupLoads
[self
::GROUP_GENERIC
][$i] > 0 );
1417 public function getServerCount() {
1418 return count( $this->servers
);
1421 public function hasReplicaServers() {
1422 return ( $this->getServerCount() > 1 );
1425 public function hasStreamingReplicaServers() {
1426 foreach ( $this->servers
as $i => $server ) {
1427 if ( $i !== $this->getWriterIndex() && empty( $server['is static'] ) ) {
1435 public function getServerName( $i ) {
1436 $name = $this->servers
[$i]['hostName'] ??
( $this->servers
[$i]['host'] ??
'' );
1438 return ( $name != '' ) ?
$name : 'localhost';
1441 public function getServerInfo( $i ) {
1442 return $this->servers
[$i] ??
false;
1445 public function getServerType( $i ) {
1446 return $this->servers
[$i]['type'] ??
'unknown';
1449 public function getMasterPos() {
1450 $index = $this->getWriterIndex();
1452 $conn = $this->getAnyOpenConnection( $index );
1454 return $conn->getMasterPos();
1457 $conn = $this->getConnection( $index, self
::CONN_SILENCE_ERRORS
);
1459 $this->reportConnectionError();
1460 return null; // unreachable due to exception
1464 $pos = $conn->getMasterPos();
1466 $this->closeConnection( $conn );
1472 public function getReplicaResumePos() {
1473 // Get the position of any existing master server connection
1474 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1475 if ( $masterConn ) {
1476 return $masterConn->getMasterPos();
1479 // Get the highest position of any existing replica server connection
1480 $highestPos = false;
1481 $serverCount = $this->getServerCount();
1482 for ( $i = 1; $i < $serverCount; $i++
) {
1483 if ( !empty( $this->servers
[$i]['is static'] ) ) {
1484 continue; // server does not use replication
1487 $conn = $this->getAnyOpenConnection( $i );
1488 $pos = $conn ?
$conn->getReplicaPos() : false;
1490 continue; // no open connection or could not get position
1493 $highestPos = $highestPos ?
: $pos;
1494 if ( $pos->hasReached( $highestPos ) ) {
1502 public function disable() {
1504 $this->disabled
= true;
1507 public function closeAll() {
1508 $fname = __METHOD__
;
1509 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( $fname ) {
1510 $host = $conn->getServer();
1511 $this->connLogger
->debug(
1512 $fname . ": closing connection to database '$host'." );
1516 $this->conns
= self
::newTrackedConnectionsArray();
1519 public function closeConnection( IDatabase
$conn ) {
1520 if ( $conn instanceof DBConnRef
) {
1521 // Avoid calling close() but still leaving the handle in the pool
1522 throw new RuntimeException( 'Cannot close DBConnRef instance; it must be shareable' );
1525 $serverIndex = $conn->getLBInfo( 'serverIndex' );
1526 foreach ( $this->conns
as $type => $connsByServer ) {
1527 if ( !isset( $connsByServer[$serverIndex] ) ) {
1531 foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1532 if ( $conn === $trackedConn ) {
1533 $host = $this->getServerName( $i );
1534 $this->connLogger
->debug(
1535 __METHOD__
. ": closing connection to database $i at '$host'." );
1536 unset( $this->conns
[$type][$serverIndex][$i] );
1545 public function commitAll( $fname = __METHOD__
, $owner = null ) {
1546 $this->commitMasterChanges( $fname, $owner );
1547 $this->flushMasterSnapshots( $fname );
1548 $this->flushReplicaSnapshots( $fname );
1551 public function finalizeMasterChanges( $fname = __METHOD__
, $owner = null ) {
1552 $this->assertOwnership( $fname, $owner );
1553 $this->assertTransactionRoundStage( [ self
::ROUND_CURSORY
, self
::ROUND_FINALIZED
] );
1555 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1556 // Loop until callbacks stop adding callbacks on other connections
1559 $count = 0; // callbacks execution attempts
1560 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( &$count ) {
1561 // Run any pre-commit callbacks while leaving the post-commit ones suppressed.
1562 // Any error should cause all (peer) transactions to be rolled back together.
1563 $count +
= $conn->runOnTransactionPreCommitCallbacks();
1566 } while ( $count > 0 );
1567 // Defer post-commit callbacks until after COMMIT/ROLLBACK happens on all handles
1568 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1569 $conn->setTrxEndCallbackSuppression( true );
1571 $this->trxRoundStage
= self
::ROUND_FINALIZED
;
1576 public function approveMasterChanges( array $options, $fname = __METHOD__
, $owner = null ) {
1577 $this->assertOwnership( $fname, $owner );
1578 $this->assertTransactionRoundStage( self
::ROUND_FINALIZED
);
1580 $limit = $options['maxWriteDuration'] ??
0;
1582 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1583 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $limit ) {
1584 // If atomic sections or explicit transactions are still open, some caller must have
1585 // caught an exception but failed to properly rollback any changes. Detect that and
1586 // throw and error (causing rollback).
1587 $conn->assertNoOpenTransactions();
1588 // Assert that the time to replicate the transaction will be sane.
1589 // If this fails, then all DB transactions will be rollback back together.
1590 $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY
);
1591 if ( $limit > 0 && $time > $limit ) {
1592 throw new DBTransactionSizeError(
1594 "Transaction spent $time second(s) in writes, exceeding the limit of $limit",
1598 // If a connection sits idle while slow queries execute on another, that connection
1599 // may end up dropped before the commit round is reached. Ping servers to detect this.
1600 if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1601 throw new DBTransactionError(
1603 "A connection to the {$conn->getDBname()} database was lost before commit"
1607 $this->trxRoundStage
= self
::ROUND_APPROVED
;
1610 public function beginMasterChanges( $fname = __METHOD__
, $owner = null ) {
1611 $this->assertOwnership( $fname, $owner );
1612 if ( $this->trxRoundId
!== false ) {
1613 throw new DBTransactionError(
1615 "$fname: Transaction round '{$this->trxRoundId}' already started"
1618 $this->assertTransactionRoundStage( self
::ROUND_CURSORY
);
1620 // Clear any empty transactions (no writes/callbacks) from the implicit round
1621 $this->flushMasterSnapshots( $fname );
1623 $this->trxRoundId
= $fname;
1624 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1625 // Mark applicable handles as participating in this explicit transaction round.
1626 // For each of these handles, any writes and callbacks will be tied to a single
1627 // transaction. The (peer) handles will reject begin()/commit() calls unless they
1628 // are part of an en masse commit or an en masse rollback.
1629 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1630 $this->applyTransactionRoundFlags( $conn );
1632 $this->trxRoundStage
= self
::ROUND_CURSORY
;
1635 public function commitMasterChanges( $fname = __METHOD__
, $owner = null ) {
1636 $this->assertOwnership( $fname, $owner );
1637 $this->assertTransactionRoundStage( self
::ROUND_APPROVED
);
1641 /** @noinspection PhpUnusedLocalVariableInspection */
1642 $scope = ScopedCallback
::newScopedIgnoreUserAbort(); // try to ignore client aborts
1644 $restore = ( $this->trxRoundId
!== false );
1645 $this->trxRoundId
= false;
1646 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1647 // Commit any writes and clear any snapshots as well (callbacks require AUTOCOMMIT).
1648 // Note that callbacks should already be suppressed due to finalizeMasterChanges().
1649 $this->forEachOpenMasterConnection(
1650 function ( IDatabase
$conn ) use ( $fname, &$failures ) {
1652 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1653 } catch ( DBError
$e ) {
1654 ( $this->errorLogger
)( $e );
1655 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1660 throw new DBTransactionError(
1662 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1666 // Unmark handles as participating in this explicit transaction round
1667 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1668 $this->undoTransactionRoundFlags( $conn );
1671 $this->trxRoundStage
= self
::ROUND_COMMIT_CALLBACKS
;
1674 public function runMasterTransactionIdleCallbacks( $fname = __METHOD__
, $owner = null ) {
1675 $this->assertOwnership( $fname, $owner );
1676 if ( $this->trxRoundStage
=== self
::ROUND_COMMIT_CALLBACKS
) {
1677 $type = IDatabase
::TRIGGER_COMMIT
;
1678 } elseif ( $this->trxRoundStage
=== self
::ROUND_ROLLBACK_CALLBACKS
) {
1679 $type = IDatabase
::TRIGGER_ROLLBACK
;
1681 throw new DBTransactionError(
1683 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1687 $oldStage = $this->trxRoundStage
;
1688 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1690 // Now that the COMMIT/ROLLBACK step is over, enable post-commit callback runs
1691 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1692 $conn->setTrxEndCallbackSuppression( false );
1695 $e = null; // first exception
1696 $fname = __METHOD__
;
1697 // Loop until callbacks stop adding callbacks on other connections
1699 // Run any pending callbacks for each connection...
1700 $count = 0; // callback execution attempts
1701 $this->forEachOpenMasterConnection(
1702 function ( Database
$conn ) use ( $type, &$e, &$count ) {
1703 if ( $conn->trxLevel() ) {
1704 return; // retry in the next iteration, after commit() is called
1707 $count +
= $conn->runOnTransactionIdleCallbacks( $type );
1708 } catch ( Exception
$ex ) {
1713 // Clear out any active transactions left over from callbacks...
1714 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( &$e, $fname ) {
1715 if ( $conn->writesPending() ) {
1716 // A callback from another handle wrote to this one and DBO_TRX is set
1717 $this->queryLogger
->warning( $fname . ": found writes pending." );
1718 $fnames = implode( ', ', $conn->pendingWriteAndCallbackCallers() );
1719 $this->queryLogger
->warning(
1720 $fname . ": found writes pending ($fnames).",
1722 'db_server' => $conn->getServer(),
1723 'db_name' => $conn->getDBname()
1726 } elseif ( $conn->trxLevel() ) {
1727 // A callback from another handle read from this one and DBO_TRX is set,
1728 // which can easily happen if there is only one DB (no replicas)
1729 $this->queryLogger
->debug( $fname . ": found empty transaction." );
1732 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1733 } catch ( Exception
$ex ) {
1737 } while ( $count > 0 );
1739 $this->trxRoundStage
= $oldStage;
1744 public function runMasterTransactionListenerCallbacks( $fname = __METHOD__
, $owner = null ) {
1745 $this->assertOwnership( $fname, $owner );
1746 if ( $this->trxRoundStage
=== self
::ROUND_COMMIT_CALLBACKS
) {
1747 $type = IDatabase
::TRIGGER_COMMIT
;
1748 } elseif ( $this->trxRoundStage
=== self
::ROUND_ROLLBACK_CALLBACKS
) {
1749 $type = IDatabase
::TRIGGER_ROLLBACK
;
1751 throw new DBTransactionError(
1753 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1759 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1760 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( $type, &$e ) {
1762 $conn->runTransactionListenerCallbacks( $type );
1763 } catch ( Exception
$ex ) {
1767 $this->trxRoundStage
= self
::ROUND_CURSORY
;
1772 public function rollbackMasterChanges( $fname = __METHOD__
, $owner = null ) {
1773 $this->assertOwnership( $fname, $owner );
1775 $restore = ( $this->trxRoundId
!== false );
1776 $this->trxRoundId
= false;
1777 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1778 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $fname ) {
1779 $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS
);
1782 // Unmark handles as participating in this explicit transaction round
1783 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1784 $this->undoTransactionRoundFlags( $conn );
1787 $this->trxRoundStage
= self
::ROUND_ROLLBACK_CALLBACKS
;
1791 * @param string|string[] $stage
1792 * @throws DBTransactionError
1794 private function assertTransactionRoundStage( $stage ) {
1795 $stages = (array)$stage;
1797 if ( !in_array( $this->trxRoundStage
, $stages, true ) ) {
1798 $stageList = implode(
1800 array_map( function ( $v ) {
1804 throw new DBTransactionError(
1806 "Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
1812 * @param string $fname
1813 * @param int|null $owner Owner ID of the caller
1814 * @throws DBTransactionError
1816 private function assertOwnership( $fname, $owner ) {
1817 if ( $this->ownerId
!== null && $owner !== $this->ownerId
) {
1818 throw new DBTransactionError(
1820 "$fname: LoadBalancer is owned by LBFactory #{$this->ownerId} (got '$owner')."
1826 * Make all DB servers with DBO_DEFAULT/DBO_TRX set join the transaction round
1828 * Some servers may have neither flag enabled, meaning that they opt out of such
1829 * transaction rounds and remain in auto-commit mode. Such behavior might be desired
1830 * when a DB server is used for something like simple key/value storage.
1832 * @param Database $conn
1834 private function applyTransactionRoundFlags( Database
$conn ) {
1835 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1836 return; // transaction rounds do not apply to these connections
1839 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1840 // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1841 // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1842 $conn->setFlag( $conn::DBO_TRX
, $conn::REMEMBER_PRIOR
);
1845 if ( $conn->getFlag( $conn::DBO_TRX
) ) {
1846 $conn->setLBInfo( 'trxRoundId', $this->trxRoundId
);
1851 * @param Database $conn
1853 private function undoTransactionRoundFlags( Database
$conn ) {
1854 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1855 return; // transaction rounds do not apply to these connections
1858 if ( $conn->getFlag( $conn::DBO_TRX
) ) {
1859 $conn->setLBInfo( 'trxRoundId', null ); // remove the round ID
1862 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1863 $conn->restoreFlags( $conn::RESTORE_PRIOR
);
1867 public function flushReplicaSnapshots( $fname = __METHOD__
) {
1868 $this->forEachOpenReplicaConnection( function ( IDatabase
$conn ) use ( $fname ) {
1869 $conn->flushSnapshot( $fname );
1873 public function flushMasterSnapshots( $fname = __METHOD__
) {
1874 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $fname ) {
1875 $conn->flushSnapshot( $fname );
1883 public function getTransactionRoundStage() {
1884 return $this->trxRoundStage
;
1887 public function hasMasterConnection() {
1888 return $this->isOpen( $this->getWriterIndex() );
1891 public function hasMasterChanges() {
1893 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$pending ) {
1894 $pending |
= $conn->writesOrCallbacksPending();
1897 return (bool)$pending;
1900 public function lastMasterChangeTimestamp() {
1902 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$lastTime ) {
1903 $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1909 public function hasOrMadeRecentMasterChanges( $age = null ) {
1910 $age = ( $age === null ) ?
$this->waitTimeout
: $age;
1912 return ( $this->hasMasterChanges()
1913 ||
$this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1916 public function pendingMasterChangeCallers() {
1918 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$fnames ) {
1919 $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1925 public function getLaggedReplicaMode( $domain = false ) {
1926 if ( $this->laggedReplicaMode
) {
1927 return true; // stay in lagged replica mode
1930 if ( $this->hasStreamingReplicaServers() ) {
1932 // Set "laggedReplicaMode"
1933 $this->getReaderIndex( self
::GROUP_GENERIC
, $domain );
1934 } catch ( DBConnectionError
$e ) {
1935 // Sanity: avoid expensive re-connect attempts and failures
1936 $this->laggedReplicaMode
= true;
1940 return $this->laggedReplicaMode
;
1943 public function laggedReplicaUsed() {
1944 return $this->laggedReplicaMode
;
1947 public function getReadOnlyReason( $domain = false, IDatabase
$conn = null ) {
1948 if ( $this->readOnlyReason
!== false ) {
1949 return $this->readOnlyReason
;
1950 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1951 return 'The master database server is running in read-only mode.';
1952 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1953 return ( $this->getExistingReaderIndex( self
::GROUP_GENERIC
) >= 0 )
1954 ?
'The database is read-only until replication lag decreases.'
1955 : 'The database is read-only until a replica database server becomes reachable.';
1962 * @param string $domain Domain ID, or false for the current domain
1963 * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1966 private function masterRunningReadOnly( $domain, IDatabase
$conn = null ) {
1967 $cache = $this->wanCache
;
1968 $masterServer = $this->getServerName( $this->getWriterIndex() );
1970 return (bool)$cache->getWithSetCallback(
1971 $cache->makeGlobalKey( __CLASS__
, 'server-read-only', $masterServer ),
1972 self
::TTL_CACHE_READONLY
,
1973 function () use ( $domain, $conn ) {
1974 $old = $this->trxProfiler
->setSilenced( true );
1976 $index = $this->getWriterIndex();
1977 $dbw = $conn ?
: $this->getServerConnection( $index, $domain );
1978 $readOnly = (int)$dbw->serverIsReadOnly();
1980 $this->reuseConnection( $dbw );
1982 } catch ( DBError
$e ) {
1985 $this->trxProfiler
->setSilenced( $old );
1989 [ 'pcTTL' => $cache::TTL_PROC_LONG
, 'busyValue' => 0 ]
1993 public function allowLagged( $mode = null ) {
1994 if ( $mode === null ) {
1995 return $this->allowLagged
;
1997 $this->allowLagged
= $mode;
1999 return $this->allowLagged
;
2002 public function pingAll() {
2004 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$success ) {
2005 if ( !$conn->ping() ) {
2013 public function forEachOpenConnection( $callback, array $params = [] ) {
2014 foreach ( $this->conns
as $connsByServer ) {
2015 foreach ( $connsByServer as $serverConns ) {
2016 foreach ( $serverConns as $conn ) {
2017 $callback( $conn, ...$params );
2023 public function forEachOpenMasterConnection( $callback, array $params = [] ) {
2024 $masterIndex = $this->getWriterIndex();
2025 foreach ( $this->conns
as $connsByServer ) {
2026 if ( isset( $connsByServer[$masterIndex] ) ) {
2027 /** @var IDatabase $conn */
2028 foreach ( $connsByServer[$masterIndex] as $conn ) {
2029 $callback( $conn, ...$params );
2035 public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
2036 foreach ( $this->conns
as $connsByServer ) {
2037 foreach ( $connsByServer as $i => $serverConns ) {
2038 if ( $i === $this->getWriterIndex() ) {
2039 continue; // skip master
2041 foreach ( $serverConns as $conn ) {
2042 $callback( $conn, ...$params );
2051 private function getCurrentConnectionCount() {
2053 foreach ( $this->conns
as $connsByServer ) {
2054 foreach ( $connsByServer as $serverConns ) {
2055 $count +
= count( $serverConns );
2062 public function getMaxLag( $domain = false ) {
2067 if ( $this->hasReplicaServers() ) {
2068 $lagTimes = $this->getLagTimes( $domain );
2069 foreach ( $lagTimes as $i => $lag ) {
2070 if ( $this->groupLoads
[self
::GROUP_GENERIC
][$i] > 0 && $lag > $maxLag ) {
2072 $host = $this->getServerInfoStrict( $i, 'host' );
2078 return [ $host, $maxLag, $maxIndex ];
2081 public function getLagTimes( $domain = false ) {
2082 if ( !$this->hasReplicaServers() ) {
2083 return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
2086 $knownLagTimes = []; // map of (server index => 0 seconds)
2087 $indexesWithLag = [];
2088 foreach ( $this->servers
as $i => $server ) {
2089 if ( empty( $server['is static'] ) ) {
2090 $indexesWithLag[] = $i; // DB server might have replication lag
2092 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
2096 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) +
$knownLagTimes;
2100 * Get the lag in seconds for a given connection, or zero if this load
2101 * balancer does not have replication enabled.
2103 * This should be used in preference to Database::getLag() in cases where
2104 * replication may not be in use, since there is no way to determine if
2105 * replication is in use at the connection level without running
2106 * potentially restricted queries such as SHOW SLAVE STATUS. Using this
2107 * function instead of Database::getLag() avoids a fatal error in this
2108 * case on many installations.
2110 * @param IDatabase $conn
2111 * @return int|bool Returns false on error
2112 * @deprecated Since 1.34 Use IDatabase::getLag() instead
2114 public function safeGetLag( IDatabase
$conn ) {
2115 if ( $conn->getLBInfo( 'is static' ) ) {
2116 return 0; // static dataset
2117 } elseif ( $conn->getLBInfo( 'serverIndex' ) == $this->getWriterIndex() ) {
2118 return 0; // this is the master
2121 return $conn->getLag();
2124 public function waitForMasterPos( IDatabase
$conn, $pos = false, $timeout = null ) {
2125 $timeout = max( 1, $timeout ?
: $this->waitTimeout
);
2127 if ( $this->getServerCount() <= 1 ||
!$conn->getLBInfo( 'replica' ) ) {
2128 return true; // server is not a replica DB
2132 // Get the current master position, opening a connection if needed
2133 $index = $this->getWriterIndex();
2134 $flags = self
::CONN_SILENCE_ERRORS
;
2135 $masterConn = $this->getAnyOpenConnection( $index, $flags );
2136 if ( $masterConn ) {
2137 $pos = $masterConn->getMasterPos();
2139 $masterConn = $this->getServerConnection( $index, self
::DOMAIN_ANY
, $flags );
2140 if ( !$masterConn ) {
2141 throw new DBReplicationWaitError(
2143 "Could not obtain a master database connection to get the position"
2146 $pos = $masterConn->getMasterPos();
2147 $this->closeConnection( $masterConn );
2151 if ( $pos instanceof DBMasterPos
) {
2152 $start = microtime( true );
2153 $result = $conn->masterPosWait( $pos, $timeout );
2154 $seconds = max( microtime( true ) - $start, 0 );
2155 if ( $result == -1 ||
is_null( $result ) ) {
2156 $msg = __METHOD__
. ': timed out waiting on {host} pos {pos} [{seconds}s]';
2157 $this->replLogger
->warning( $msg, [
2158 'host' => $conn->getServer(),
2160 'seconds' => round( $seconds, 6 ),
2161 'trace' => ( new RuntimeException() )->getTraceAsString()
2165 $this->replLogger
->debug( __METHOD__
. ': done waiting' );
2169 $ok = false; // something is misconfigured
2170 $this->replLogger
->error(
2171 __METHOD__
. ': could not get master pos for {host}',
2173 'host' => $conn->getServer(),
2174 'trace' => ( new RuntimeException() )->getTraceAsString()
2183 * Wait for a replica DB to reach a specified master position
2185 * This will connect to the master to get an accurate position if $pos is not given
2187 * @param IDatabase $conn Replica DB
2188 * @param DBMasterPos|bool $pos Master position; default: current position
2189 * @param int $timeout Timeout in seconds [optional]
2190 * @return bool Success
2192 * @deprecated Since 1.34 Use waitForMasterPos() instead
2194 public function safeWaitForMasterPos( IDatabase
$conn, $pos = false, $timeout = null ) {
2195 return $this->waitForMasterPos( $conn, $pos, $timeout );
2198 public function setTransactionListener( $name, callable
$callback = null ) {
2200 $this->trxRecurringCallbacks
[$name] = $callback;
2202 unset( $this->trxRecurringCallbacks
[$name] );
2204 $this->forEachOpenMasterConnection(
2205 function ( IDatabase
$conn ) use ( $name, $callback ) {
2206 $conn->setTransactionListener( $name, $callback );
2211 public function setTableAliases( array $aliases ) {
2212 $this->tableAliases
= $aliases;
2215 public function setIndexAliases( array $aliases ) {
2216 $this->indexAliases
= $aliases;
2219 public function setLocalDomainPrefix( $prefix ) {
2220 // Find connections to explicit foreign domains still marked as in-use...
2222 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$domainsInUse ) {
2223 // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
2224 // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
2225 if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
2226 $domainsInUse[] = $conn->getDomainID();
2230 // Do not switch connections to explicit foreign domains unless marked as safe
2231 if ( $domainsInUse ) {
2232 $domains = implode( ', ', $domainsInUse );
2233 throw new DBUnexpectedError( null,
2234 "Foreign domain connections are still in use ($domains)" );
2237 $this->setLocalDomain( new DatabaseDomain(
2238 $this->localDomain
->getDatabase(),
2239 $this->localDomain
->getSchema(),
2243 // Update the prefix for all local connections...
2244 $this->forEachOpenConnection( function ( IDatabase
$db ) use ( $prefix ) {
2245 if ( !$db->getLBInfo( 'foreign' ) ) {
2246 $db->tablePrefix( $prefix );
2251 public function redefineLocalDomain( $domain ) {
2254 $this->setLocalDomain( DatabaseDomain
::newFromId( $domain ) );
2257 public function setTempTablesOnlyMode( $value, $domain ) {
2258 $old = $this->tempTablesOnlyMode
[$domain] ??
false;
2260 $this->tempTablesOnlyMode
[$domain] = true;
2262 unset( $this->tempTablesOnlyMode
[$domain] );
2269 * @param DatabaseDomain $domain
2271 private function setLocalDomain( DatabaseDomain
$domain ) {
2272 $this->localDomain
= $domain;
2273 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
2274 // always true, gracefully handle the case when they fail to account for escaping.
2275 if ( $this->localDomain
->getTablePrefix() != '' ) {
2276 $this->localDomainIdAlias
=
2277 $this->localDomain
->getDatabase() . '-' . $this->localDomain
->getTablePrefix();
2279 $this->localDomainIdAlias
= $this->localDomain
->getDatabase();
2284 * @param int $i Server index
2285 * @param string|null $field Server index field [optional]
2286 * @return array|mixed
2287 * @throws InvalidArgumentException
2289 private function getServerInfoStrict( $i, $field = null ) {
2290 if ( !isset( $this->servers
[$i] ) ||
!is_array( $this->servers
[$i] ) ) {
2291 throw new InvalidArgumentException( "No server with index '$i'" );
2294 if ( $field !== null ) {
2295 if ( !array_key_exists( $field, $this->servers
[$i] ) ) {
2296 throw new InvalidArgumentException( "No field '$field' in server index '$i'" );
2299 return $this->servers
[$i][$field];
2302 return $this->servers
[$i];
2305 function __destruct() {
2306 // Avoid connection leaks for sanity
2312 * @deprecated since 1.29
2314 class_alias( LoadBalancer
::class, 'LoadBalancer' );