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 */
72 * @var IDatabase[][][]|Database[][][] Map of (connection category => server index => IDatabase[])
76 /** @var array[] Map of (server index => server config array) */
78 /** @var array[] Map of (group => server index => weight) */
80 /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
82 /** @var int Seconds to spend waiting on replica DB lag to resolve */
84 /** @var array The LoadMonitor configuration */
85 private $loadMonitorConfig;
86 /** @var string Alternate local DB domain instead of DatabaseDomain::getId() */
87 private $localDomainIdAlias;
88 /** @var int Amount of replication lag, in seconds, that is considered "high" */
90 /** @var string|null Default query group to use with getConnection() */
91 private $defaultGroup;
93 /** @var string Current server name */
95 /** @var bool Whether this PHP instance is for a CLI script */
97 /** @var string Agent name for query profiling */
100 /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
101 private $tableAliases = [];
102 /** @var string[] Map of (index alias => index) */
103 private $indexAliases = [];
104 /** @var callable[] Map of (name => callable) */
105 private $trxRecurringCallbacks = [];
106 /** @var bool[] Map of (domain => whether to use "temp tables only" mode) */
107 private $tempTablesOnlyMode = [];
109 /** @var Database Connection handle that caused a problem */
110 private $errorConnection;
111 /** @var int[] The group replica server indexes keyed by group */
112 private $readIndexByGroup = [];
113 /** @var bool|DBMasterPos Replication sync position or false if not set */
115 /** @var bool Whether the generic reader fell back to a lagged replica DB */
116 private $laggedReplicaMode = false;
117 /** @var string The last DB selection or connection error */
118 private $lastError = 'Unknown error';
119 /** @var string|bool Reason this instance is read-only or false if not */
120 private $readOnlyReason = false;
121 /** @var int Total number of new connections ever made with this instance */
122 private $connectionCounter = 0;
124 private $disabled = false;
125 /** @var bool Whether any connection has been attempted yet */
126 private $connectionAttempted = false;
128 /** @var int|null Integer ID of the managing LBFactory instance or null if none */
130 /** @var string|bool Explicit DBO_TRX transaction round active or false if none */
131 private $trxRoundId = false;
132 /** @var string Stage of the current transaction round in the transaction round life-cycle */
133 private $trxRoundStage = self
::ROUND_CURSORY
;
135 /** @var int Warn when this many connection are held */
136 const CONN_HELD_WARN_THRESHOLD
= 10;
138 /** @var int Default 'maxLag' when unspecified */
139 const MAX_LAG_DEFAULT
= 6;
140 /** @var int Default 'waitTimeout' when unspecified */
141 const MAX_WAIT_DEFAULT
= 10;
142 /** @var int Seconds to cache master DB server read-only status */
143 const TTL_CACHE_READONLY
= 5;
145 const KEY_LOCAL
= 'local';
146 const KEY_FOREIGN_FREE
= 'foreignFree';
147 const KEY_FOREIGN_INUSE
= 'foreignInUse';
149 const KEY_LOCAL_NOROUND
= 'localAutoCommit';
150 const KEY_FOREIGN_FREE_NOROUND
= 'foreignFreeAutoCommit';
151 const KEY_FOREIGN_INUSE_NOROUND
= 'foreignInUseAutoCommit';
153 /** @var string Transaction round, explicit or implicit, has not finished writing */
154 const ROUND_CURSORY
= 'cursory';
155 /** @var string Transaction round writes are complete and ready for pre-commit checks */
156 const ROUND_FINALIZED
= 'finalized';
157 /** @var string Transaction round passed final pre-commit checks */
158 const ROUND_APPROVED
= 'approved';
159 /** @var string Transaction round was committed and post-commit callbacks must be run */
160 const ROUND_COMMIT_CALLBACKS
= 'commit-callbacks';
161 /** @var string Transaction round was rolled back and post-rollback callbacks must be run */
162 const ROUND_ROLLBACK_CALLBACKS
= 'rollback-callbacks';
163 /** @var string Transaction round encountered an error */
164 const ROUND_ERROR
= 'error';
166 public function __construct( array $params ) {
167 if ( !isset( $params['servers'] ) ||
!count( $params['servers'] ) ) {
168 throw new InvalidArgumentException( 'Missing or empty "servers" parameter' );
173 $this->groupLoads
= [ self
::GROUP_GENERIC
=> [] ];
174 foreach ( $params['servers'] as $i => $server ) {
175 if ( ++
$listKey !== $i ) {
176 throw new UnexpectedValueException( 'List expected for "servers" parameter' );
179 $server['master'] = true;
181 $server['replica'] = true;
183 $this->servers
[$i] = $server;
184 foreach ( ( $server['groupLoads'] ??
[] ) as $group => $ratio ) {
185 $this->groupLoads
[$group][$i] = $ratio;
187 $this->groupLoads
[self
::GROUP_GENERIC
][$i] = $server['load'];
190 $localDomain = isset( $params['localDomain'] )
191 ? DatabaseDomain
::newFromId( $params['localDomain'] )
192 : DatabaseDomain
::newUnspecified();
193 $this->setLocalDomain( $localDomain );
195 $this->waitTimeout
= $params['waitTimeout'] ?? self
::MAX_WAIT_DEFAULT
;
197 $this->conns
= self
::newTrackedConnectionsArray();
198 $this->waitForPos
= false;
199 $this->allowLagged
= false;
201 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
202 $this->readOnlyReason
= $params['readOnlyReason'];
205 $this->maxLag
= $params['maxLag'] ?? self
::MAX_LAG_DEFAULT
;
207 $this->loadMonitorConfig
= $params['loadMonitor'] ??
[ 'class' => 'LoadMonitorNull' ];
208 $this->loadMonitorConfig +
= [ 'lagWarnThreshold' => $this->maxLag
];
210 $this->srvCache
= $params['srvCache'] ??
new EmptyBagOStuff();
211 $this->wanCache
= $params['wanCache'] ?? WANObjectCache
::newEmpty();
212 $this->profiler
= $params['profiler'] ??
null;
213 $this->trxProfiler
= $params['trxProfiler'] ??
new TransactionProfiler();
215 $this->errorLogger
= $params['errorLogger'] ??
function ( Exception
$e ) {
216 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING
);
218 $this->deprecationLogger
= $params['deprecationLogger'] ??
function ( $msg ) {
219 trigger_error( $msg, E_USER_DEPRECATED
);
222 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
223 $this->$key = $params[$key] ??
new NullLogger();
226 $this->hostname
= $params['hostname'] ??
( gethostname() ?
: 'unknown' );
227 $this->cliMode
= $params['cliMode'] ??
( PHP_SAPI
=== 'cli' || PHP_SAPI
=== 'phpdbg' );
228 $this->agent
= $params['agent'] ??
'';
230 if ( isset( $params['chronologyCallback'] ) ) {
231 $this->chronologyCallback
= $params['chronologyCallback'];
234 if ( isset( $params['roundStage'] ) ) {
235 if ( $params['roundStage'] === self
::STAGE_POSTCOMMIT_CALLBACKS
) {
236 $this->trxRoundStage
= self
::ROUND_COMMIT_CALLBACKS
;
237 } elseif ( $params['roundStage'] === self
::STAGE_POSTROLLBACK_CALLBACKS
) {
238 $this->trxRoundStage
= self
::ROUND_ROLLBACK_CALLBACKS
;
242 $group = $params['defaultGroup'] ?? self
::GROUP_GENERIC
;
243 $this->defaultGroup
= isset( $this->groupLoads
[$group] ) ?
$group : self
::GROUP_GENERIC
;
245 $this->ownerId
= $params['ownerId'] ??
null;
248 private static function newTrackedConnectionsArray() {
250 // Connection were transaction rounds may be applied
251 self
::KEY_LOCAL
=> [],
252 self
::KEY_FOREIGN_INUSE
=> [],
253 self
::KEY_FOREIGN_FREE
=> [],
254 // Auto-committing counterpart connections that ignore transaction rounds
255 self
::KEY_LOCAL_NOROUND
=> [],
256 self
::KEY_FOREIGN_INUSE_NOROUND
=> [],
257 self
::KEY_FOREIGN_FREE_NOROUND
=> []
261 public function getLocalDomainID() {
262 return $this->localDomain
->getId();
265 public function resolveDomainID( $domain ) {
266 if ( $domain === $this->localDomainIdAlias ||
$domain === false ) {
267 // Local connection requested via some backwards-compatibility domain alias
268 return $this->getLocalDomainID();
271 return (string)$domain;
275 * Resolve $groups into a list of query groups defining as having database servers
277 * @param string[]|string|bool $groups Query group(s) in preference order, [], or false
278 * @param int $i Specific server index or DB_MASTER/DB_REPLICA
279 * @return string[] Non-empty group list in preference order with the default group appended
281 private function resolveGroups( $groups, $i ) {
282 // If a specific replica server was specified, then $groups makes no sense
283 if ( $i > 0 && $groups !== [] && $groups !== false ) {
284 $list = implode( ', ', (array)$groups );
285 throw new LogicException( "Query group(s) ($list) given with server index (#$i)" );
288 if ( $groups === [] ||
$groups === false ||
$groups === $this->defaultGroup
) {
289 $resolvedGroups = [ $this->defaultGroup
]; // common case
290 } elseif ( is_string( $groups ) && isset( $this->groupLoads
[$groups] ) ) {
291 $resolvedGroups = [ $groups, $this->defaultGroup
];
292 } elseif ( is_array( $groups ) ) {
293 $resolvedGroups = array_keys( array_flip( $groups ) +
[ self
::GROUP_GENERIC
=> 1 ] );
295 $resolvedGroups = [ $this->defaultGroup
];
298 return $resolvedGroups;
302 * @param int $flags Bitfield of class CONN_* constants
303 * @param int $i Specific server index or DB_MASTER/DB_REPLICA
304 * @param string $domain Database domain
305 * @return int Sanitized bitfield
307 private function sanitizeConnectionFlags( $flags, $i, $domain ) {
308 // Whether an outside caller is explicitly requesting the master database server
309 if ( $i === self
::DB_MASTER ||
$i === $this->getWriterIndex() ) {
310 $flags |
= self
::CONN_INTENT_WRITABLE
;
313 if ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
) {
314 // Callers use CONN_TRX_AUTOCOMMIT to bypass REPEATABLE-READ staleness without
315 // resorting to row locks (e.g. FOR UPDATE) or to make small out-of-band commits
316 // during larger transactions. This is useful for avoiding lock contention.
318 // Master DB server attributes (should match those of the replica DB servers)
319 $attributes = $this->getServerAttributes( $this->getWriterIndex() );
320 if ( $attributes[Database
::ATTR_DB_LEVEL_LOCKING
] ) {
321 // The RDBMS does not support concurrent writes (e.g. SQLite), so attempts
322 // to use separate connections would just cause self-deadlocks. Note that
323 // REPEATABLE-READ staleness is not an issue since DB-level locking means
324 // that transactions are Strict Serializable anyway.
325 $flags &= ~self
::CONN_TRX_AUTOCOMMIT
;
326 $type = $this->getServerType( $this->getWriterIndex() );
327 $this->connLogger
->info( __METHOD__
. ": CONN_TRX_AUTOCOMMIT disallowed ($type)" );
328 } elseif ( isset( $this->tempTablesOnlyMode
[$domain] ) ) {
329 // T202116: integration tests are active and queries should be all be using
330 // temporary clone tables (via prefix). Such tables are not visible accross
331 // different connections nor can there be REPEATABLE-READ snapshot staleness,
332 // so use the same connection for everything.
333 $flags &= ~self
::CONN_TRX_AUTOCOMMIT
;
341 * @param IDatabase $conn
343 * @throws DBUnexpectedError
345 private function enforceConnectionFlags( IDatabase
$conn, $flags ) {
346 if ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
) {
347 if ( $conn->trxLevel() ) { // sanity
348 throw new DBUnexpectedError(
350 'Handle requested with CONN_TRX_AUTOCOMMIT yet it has a transaction'
354 $conn->clearFlag( $conn::DBO_TRX
); // auto-commit mode
359 * Get a LoadMonitor instance
361 * @return ILoadMonitor
363 private function getLoadMonitor() {
364 if ( !isset( $this->loadMonitor
) ) {
366 'LoadMonitor' => LoadMonitor
::class,
367 'LoadMonitorNull' => LoadMonitorNull
::class,
368 'LoadMonitorMySQL' => LoadMonitorMySQL
::class,
371 $class = $this->loadMonitorConfig
['class'];
372 if ( isset( $compat[$class] ) ) {
373 $class = $compat[$class];
376 $this->loadMonitor
= new $class(
377 $this, $this->srvCache
, $this->wanCache
, $this->loadMonitorConfig
);
378 $this->loadMonitor
->setLogger( $this->replLogger
);
381 return $this->loadMonitor
;
385 * @param array $loads
386 * @param bool|string $domain Domain to get non-lagged for
387 * @param int $maxLag Restrict the maximum allowed lag to this many seconds
388 * @return bool|int|string
390 private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF
) {
391 $lags = $this->getLagTimes( $domain );
393 # Unset excessively lagged servers
394 foreach ( $lags as $i => $lag ) {
395 if ( $i !== $this->getWriterIndex() ) {
396 # How much lag this server nominally is allowed to have
397 $maxServerLag = $this->servers
[$i]['max lag'] ??
$this->maxLag
; // default
398 # Constrain that futher by $maxLag argument
399 $maxServerLag = min( $maxServerLag, $maxLag );
401 $host = $this->getServerName( $i );
402 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
403 $this->replLogger
->debug(
405 ": server {host} is not replicating?", [ 'host' => $host ] );
407 } elseif ( $lag > $maxServerLag ) {
408 $this->replLogger
->debug(
410 ": server {host} has {lag} seconds of lag (>= {maxlag})",
411 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
418 # Find out if all the replica DBs with non-zero load are lagged
420 foreach ( $loads as $load ) {
424 # No appropriate DB servers except maybe the master and some replica DBs with zero load
425 # Do NOT use the master
426 # Instead, this function will return false, triggering read-only mode,
427 # and a lagged replica DB will be used instead.
431 if ( count( $loads ) == 0 ) {
435 # Return a random representative of the remainder
436 return ArrayUtils
::pickRandom( $loads );
440 * Get the server index to use for a specified server index and query group list
442 * @param int $i Specific server index or DB_MASTER/DB_REPLICA
443 * @param string[] $groups Non-empty query group list in preference order
444 * @param string|bool $domain
445 * @return int A specific server index (replica DBs are checked for connectivity)
447 private function getConnectionIndex( $i, array $groups, $domain ) {
448 if ( $i === self
::DB_MASTER
) {
449 $i = $this->getWriterIndex();
450 } elseif ( $i === self
::DB_REPLICA
) {
451 foreach ( $groups as $group ) {
452 $groupIndex = $this->getReaderIndex( $group, $domain );
453 if ( $groupIndex !== false ) {
454 $i = $groupIndex; // group connection succeeded
458 } elseif ( !isset( $this->servers
[$i] ) ) {
459 throw new UnexpectedValueException( "Invalid server index index #$i" );
462 if ( $i === self
::DB_REPLICA
) {
463 $this->lastError
= 'Unknown error'; // set here in case of worse failure
464 $this->lastError
= 'No working replica DB server: ' . $this->lastError
;
465 $this->reportConnectionError();
466 return null; // unreachable due to exception
472 public function getReaderIndex( $group = false, $domain = false ) {
473 if ( $this->getServerCount() == 1 ) {
474 // Skip the load balancing if there's only one server
475 return $this->getWriterIndex();
478 $group = is_string( $group ) ?
$group : self
::GROUP_GENERIC
;
480 $index = $this->getExistingReaderIndex( $group );
482 // A reader index was already selected and "waitForPos" was handled
486 // Use the server weight array for this load group
487 if ( isset( $this->groupLoads
[$group] ) ) {
488 $loads = $this->groupLoads
[$group];
490 $this->connLogger
->info( __METHOD__
. ": no loads for group $group" );
495 // Scale the configured load ratios according to each server's load and state
496 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
498 // Pick a server to use, accounting for weights, load, lag, and "waitForPos"
499 $this->lazyLoadReplicationPositions(); // optimizes server candidate selection
500 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
501 if ( $i === false ) {
502 // DB connection unsuccessful
506 // If data seen by queries is expected to reflect the transactions committed as of
507 // or after a given replication position then wait for the DB to apply those changes
508 if ( $this->waitForPos
&& $i !== $this->getWriterIndex() && !$this->doWait( $i ) ) {
509 // Data will be outdated compared to what was expected
510 $laggedReplicaMode = true;
513 // Cache the reader index for future DB_REPLICA handles
514 $this->setExistingReaderIndex( $group, $i );
515 // Record whether the generic reader index is in "lagged replica DB" mode
516 if ( $group === self
::GROUP_GENERIC
&& $laggedReplicaMode ) {
517 $this->laggedReplicaMode
= true;
520 $serverName = $this->getServerName( $i );
521 $this->connLogger
->debug( __METHOD__
. ": using server $serverName for group '$group'" );
527 * Get the server index chosen by the load balancer for use with the given query group
529 * @param string $group Query group; use false for the generic group
530 * @return int Server index or -1 if none was chosen
532 protected function getExistingReaderIndex( $group ) {
533 return $this->readIndexByGroup
[$group] ??
-1;
537 * Set the server index chosen by the load balancer for use with the given query group
539 * @param string $group Query group; use false for the generic group
540 * @param int $index The index of a specific server
542 private function setExistingReaderIndex( $group, $index ) {
544 throw new UnexpectedValueException( "Cannot set a negative read server index" );
546 $this->readIndexByGroup
[$group] = $index;
550 * @param array $loads List of server weights
551 * @param string|bool $domain
552 * @return array (reader index, lagged replica mode) or (false, false) on failure
554 private function pickReaderIndex( array $loads, $domain = false ) {
555 if ( $loads === [] ) {
556 throw new InvalidArgumentException( "Server configuration array is empty" );
559 /** @var int|bool $i Index of selected server */
561 /** @var bool $laggedReplicaMode Whether server is considered lagged */
562 $laggedReplicaMode = false;
564 // Quickly look through the available servers for a server that meets criteria...
565 $currentLoads = $loads;
566 while ( count( $currentLoads ) ) {
567 if ( $this->allowLagged ||
$laggedReplicaMode ) {
568 $i = ArrayUtils
::pickRandom( $currentLoads );
571 if ( $this->waitForPos
&& $this->waitForPos
->asOfTime() ) {
572 $this->replLogger
->debug( __METHOD__
. ": replication positions detected" );
573 // "chronologyCallback" sets "waitForPos" for session consistency.
574 // This triggers doWait() after connect, so it's especially good to
575 // avoid lagged servers so as to avoid excessive delay in that method.
576 $ago = microtime( true ) - $this->waitForPos
->asOfTime();
577 // Aim for <= 1 second of waiting (being too picky can backfire)
578 $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago +
1 );
580 if ( $i === false ) {
581 // Any server with less lag than it's 'max lag' param is preferable
582 $i = $this->getRandomNonLagged( $currentLoads, $domain );
584 if ( $i === false && count( $currentLoads ) ) {
585 // All replica DBs lagged. Switch to read-only mode
586 $this->replLogger
->error(
587 __METHOD__
. ": all replica DBs lagged. Switch to read-only mode" );
588 $i = ArrayUtils
::pickRandom( $currentLoads );
589 $laggedReplicaMode = true;
593 if ( $i === false ) {
594 // pickRandom() returned false.
595 // This is permanent and means the configuration or the load monitor
596 // wants us to return false.
597 $this->connLogger
->debug( __METHOD__
. ": pickRandom() returned false" );
599 return [ false, false ];
602 $serverName = $this->getServerName( $i );
603 $this->connLogger
->debug( __METHOD__
. ": Using reader #$i: $serverName..." );
605 // Get a connection to this server without triggering other server connections
606 $conn = $this->getServerConnection( $i, $domain, self
::CONN_SILENCE_ERRORS
);
608 $this->connLogger
->warning( __METHOD__
. ": Failed connecting to $i/$domain" );
609 unset( $currentLoads[$i] ); // avoid this server next iteration
614 // Decrement reference counter, we are finished with this connection.
615 // It will be incremented for the caller later.
616 if ( $domain !== false ) {
617 $this->reuseConnection( $conn );
620 // Return this server
624 // If all servers were down, quit now
625 if ( $currentLoads === [] ) {
626 $this->connLogger
->error( __METHOD__
. ": all servers down" );
629 return [ $i, $laggedReplicaMode ];
632 public function waitFor( $pos ) {
633 $oldPos = $this->waitForPos
;
635 $this->waitForPos
= $pos;
636 // If a generic reader connection was already established, then wait now
637 $i = $this->getExistingReaderIndex( self
::GROUP_GENERIC
);
638 if ( $i > 0 && !$this->doWait( $i ) ) {
639 $this->laggedReplicaMode
= true;
641 // Otherwise, wait until a connection is established in getReaderIndex()
643 // Restore the older position if it was higher since this is used for lag-protection
644 $this->setWaitForPositionIfHigher( $oldPos );
648 public function waitForOne( $pos, $timeout = null ) {
649 $oldPos = $this->waitForPos
;
651 $this->waitForPos
= $pos;
653 $i = $this->getExistingReaderIndex( self
::GROUP_GENERIC
);
655 // Pick a generic replica DB if there isn't one yet
656 $readLoads = $this->groupLoads
[self
::GROUP_GENERIC
];
657 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
658 $readLoads = array_filter( $readLoads ); // with non-zero load
659 $i = ArrayUtils
::pickRandom( $readLoads );
663 $ok = $this->doWait( $i, true, $timeout );
665 $ok = true; // no applicable loads
668 // Restore the old position; this is used for throttling, not lag-protection
669 $this->waitForPos
= $oldPos;
675 public function waitForAll( $pos, $timeout = null ) {
676 $timeout = $timeout ?
: $this->waitTimeout
;
678 $oldPos = $this->waitForPos
;
680 $this->waitForPos
= $pos;
681 $serverCount = $this->getServerCount();
684 for ( $i = 1; $i < $serverCount; $i++
) {
685 if ( $this->serverHasLoadInAnyGroup( $i ) ) {
686 $start = microtime( true );
687 $ok = $this->doWait( $i, true, $timeout ) && $ok;
688 $timeout -= intval( microtime( true ) - $start );
689 if ( $timeout <= 0 ) {
690 break; // timeout reached
695 // Restore the old position; this is used for throttling, not lag-protection
696 $this->waitForPos
= $oldPos;
703 * @param int $i Specific server index
706 private function serverHasLoadInAnyGroup( $i ) {
707 foreach ( $this->groupLoads
as $loadsByIndex ) {
708 if ( ( $loadsByIndex[$i] ??
0 ) > 0 ) {
717 * @param DBMasterPos|bool $pos
719 private function setWaitForPositionIfHigher( $pos ) {
724 if ( !$this->waitForPos ||
$pos->hasReached( $this->waitForPos
) ) {
725 $this->waitForPos
= $pos;
729 public function getAnyOpenConnection( $i, $flags = 0 ) {
730 $i = ( $i === self
::DB_MASTER
) ?
$this->getWriterIndex() : $i;
731 // Connection handles required to be in auto-commit mode use a separate connection
732 // pool since the main pool is effected by implicit and explicit transaction rounds
733 $autocommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
736 foreach ( $this->conns
as $connsByServer ) {
737 // Get the connection array server indexes to inspect
738 if ( $i === self
::DB_REPLICA
) {
739 $indexes = array_keys( $connsByServer );
741 $indexes = isset( $connsByServer[$i] ) ?
[ $i ] : [];
744 foreach ( $indexes as $index ) {
745 $conn = $this->pickAnyOpenConnection( $connsByServer[$index], $autocommit );
753 $this->enforceConnectionFlags( $conn, $flags );
760 * @param IDatabase[] $candidateConns
761 * @param bool $autocommit Whether to only look for auto-commit connections
762 * @return IDatabase|false An appropriate open connection or false if none found
764 private function pickAnyOpenConnection( $candidateConns, $autocommit ) {
767 foreach ( $candidateConns as $candidateConn ) {
768 if ( !$candidateConn->isOpen() ) {
769 continue; // some sort of error occured?
773 // Connection is transaction round aware
774 !$candidateConn->getLBInfo( 'autoCommitOnly' ) ||
775 // Some sort of error left a transaction open?
776 $candidateConn->trxLevel()
779 continue; // some sort of error left a transaction open?
782 $conn = $candidateConn;
789 * Wait for a given replica DB to catch up to the master pos stored in "waitForPos"
790 * @param int $index Specific server index
791 * @param bool $open Check the server even if a new connection has to be made
792 * @param int|null $timeout Max seconds to wait; default is "waitTimeout"
795 protected function doWait( $index, $open = false, $timeout = null ) {
796 $timeout = max( 1, intval( $timeout ?
: $this->waitTimeout
) );
798 // Check if we already know that the DB has reached this point
799 $server = $this->getServerName( $index );
800 $key = $this->srvCache
->makeGlobalKey( __CLASS__
, 'last-known-pos', $server, 'v1' );
801 /** @var DBMasterPos $knownReachedPos */
802 $knownReachedPos = $this->srvCache
->get( $key );
804 $knownReachedPos instanceof DBMasterPos
&&
805 $knownReachedPos->hasReached( $this->waitForPos
)
807 $this->replLogger
->debug(
809 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
810 [ 'dbserver' => $server ]
815 // Find a connection to wait on, creating one if needed and allowed
816 $close = false; // close the connection afterwards
817 $flags = self
::CONN_SILENCE_ERRORS
;
818 $conn = $this->getAnyOpenConnection( $index, $flags );
821 $this->replLogger
->debug(
822 __METHOD__
. ': no connection open for {dbserver}',
823 [ 'dbserver' => $server ]
828 // Get a connection to this server without triggering other server connections
829 $conn = $this->getServerConnection( $index, self
::DOMAIN_ANY
, $flags );
831 $this->replLogger
->warning(
832 __METHOD__
. ': failed to connect to {dbserver}',
833 [ 'dbserver' => $server ]
838 // Avoid connection spam in waitForAll() when connections
839 // are made just for the sake of doing this lag check.
843 $this->replLogger
->info(
845 ': waiting for replica DB {dbserver} to catch up...',
846 [ 'dbserver' => $server ]
849 $result = $conn->masterPosWait( $this->waitForPos
, $timeout );
851 if ( $result === null ) {
852 $this->replLogger
->warning(
853 __METHOD__
. ': Errored out waiting on {host} pos {pos}',
856 'pos' => $this->waitForPos
,
857 'trace' => ( new RuntimeException() )->getTraceAsString()
861 } elseif ( $result == -1 ) {
862 $this->replLogger
->warning(
863 __METHOD__
. ': Timed out waiting on {host} pos {pos}',
866 'pos' => $this->waitForPos
,
867 'trace' => ( new RuntimeException() )->getTraceAsString()
872 $this->replLogger
->debug( __METHOD__
. ": done waiting" );
874 // Remember that the DB reached this point
875 $this->srvCache
->set( $key, $this->waitForPos
, BagOStuff
::TTL_DAY
);
879 $this->closeConnection( $conn );
885 public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
886 $domain = $this->resolveDomainID( $domain );
887 $groups = $this->resolveGroups( $groups, $i );
888 $flags = $this->sanitizeConnectionFlags( $flags, $i, $domain );
889 // If given DB_MASTER/DB_REPLICA, resolve it to a specific server index. Resolving
890 // DB_REPLICA might trigger getServerConnection() calls due to the getReaderIndex()
891 // connectivity checks or LoadMonitor::scaleLoads() server state cache regeneration.
892 // The use of getServerConnection() instead of getConnection() avoids infinite loops.
893 $serverIndex = $this->getConnectionIndex( $i, $groups, $domain );
894 // Get an open connection to that server (might trigger a new connection)
895 $conn = $this->getServerConnection( $serverIndex, $domain, $flags );
896 // Set master DB handles as read-only if there is high replication lag
898 $serverIndex === $this->getWriterIndex() &&
899 $this->getLaggedReplicaMode( $domain ) &&
900 !is_string( $conn->getLBInfo( 'readOnlyReason' ) )
902 $reason = ( $this->getExistingReaderIndex( self
::GROUP_GENERIC
) >= 0 )
903 ?
'The database is read-only until replication lag decreases.'
904 : 'The database is read-only until replica database servers becomes reachable.';
905 $conn->setLBInfo( 'readOnlyReason', $reason );
912 * @param int $i Specific server index
913 * @param string $domain Resolved DB domain
914 * @param int $flags Bitfield of class CONN_* constants
915 * @return IDatabase|bool
916 * @throws InvalidArgumentException When the server index is invalid
918 public function getServerConnection( $i, $domain, $flags = 0 ) {
919 // Number of connections made before getting the server index and handle
920 $priorConnectionsMade = $this->connectionCounter
;
921 // Get an open connection to this server (might trigger a new connection)
922 $conn = $this->localDomain
->equals( $domain )
923 ?
$this->getLocalConnection( $i, $flags )
924 : $this->getForeignConnection( $i, $domain, $flags );
925 // Throw an error or otherwise bail out if the connection attempt failed
926 if ( !( $conn instanceof IDatabase
) ) {
927 if ( ( $flags & self
::CONN_SILENCE_ERRORS
) != self
::CONN_SILENCE_ERRORS
) {
928 $this->reportConnectionError();
934 // Profile any new connections caused by this method
935 if ( $this->connectionCounter
> $priorConnectionsMade ) {
936 $this->trxProfiler
->recordConnection(
939 ( ( $flags & self
::CONN_INTENT_WRITABLE
) == self
::CONN_INTENT_WRITABLE
)
943 if ( !$conn->isOpen() ) {
944 $this->errorConnection
= $conn;
945 // Connection was made but later unrecoverably lost for some reason.
946 // Do not return a handle that will just throw exceptions on use, but
947 // let the calling code, e.g. getReaderIndex(), try another server.
951 // Make sure that flags like CONN_TRX_AUTOCOMMIT are respected by this handle
952 $this->enforceConnectionFlags( $conn, $flags );
953 // Set master DB handles as read-only if the load balancer is configured as read-only
954 // or the master database server is running in server-side read-only mode. Note that
955 // replica DB handles are always read-only via Database::assertIsWritableMaster().
956 // Read-only mode due to replication lag is *avoided* here to avoid recursion.
957 if ( $i === $this->getWriterIndex() ) {
958 if ( $this->readOnlyReason
!== false ) {
959 $readOnlyReason = $this->readOnlyReason
;
960 } elseif ( $this->isMasterConnectionReadOnly( $conn, $flags ) ) {
961 $readOnlyReason = 'The master database server is running in read-only mode.';
963 $readOnlyReason = false;
965 $conn->setLBInfo( 'readOnlyReason', $readOnlyReason );
971 public function reuseConnection( IDatabase
$conn ) {
972 $serverIndex = $conn->getLBInfo( 'serverIndex' );
973 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
974 if ( $serverIndex === null ||
$refCount === null ) {
975 return; // non-foreign connection; no domain-use tracking to update
976 } elseif ( $conn instanceof DBConnRef
) {
977 // DBConnRef already handles calling reuseConnection() and only passes the live
978 // Database instance to this method. Any caller passing in a DBConnRef is broken.
979 $this->connLogger
->error(
980 __METHOD__
. ": got DBConnRef instance.\n" .
981 ( new LogicException() )->getTraceAsString() );
986 if ( $this->disabled
) {
987 return; // DBConnRef handle probably survived longer than the LoadBalancer
990 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
991 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
992 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
994 $connFreeKey = self
::KEY_FOREIGN_FREE
;
995 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
998 $domain = $conn->getDomainID();
999 if ( !isset( $this->conns
[$connInUseKey][$serverIndex][$domain] ) ) {
1000 throw new InvalidArgumentException(
1001 "Connection $serverIndex/$domain not found; it may have already been freed" );
1002 } elseif ( $this->conns
[$connInUseKey][$serverIndex][$domain] !== $conn ) {
1003 throw new InvalidArgumentException(
1004 "Connection $serverIndex/$domain mismatched; it may have already been freed" );
1007 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
1008 if ( $refCount <= 0 ) {
1009 $this->conns
[$connFreeKey][$serverIndex][$domain] = $conn;
1010 unset( $this->conns
[$connInUseKey][$serverIndex][$domain] );
1011 if ( !$this->conns
[$connInUseKey][$serverIndex] ) {
1012 unset( $this->conns
[$connInUseKey][$serverIndex] ); // clean up
1014 $this->connLogger
->debug( __METHOD__
. ": freed connection $serverIndex/$domain" );
1016 $this->connLogger
->debug( __METHOD__
.
1017 ": reference count for $serverIndex/$domain reduced to $refCount" );
1021 public function getConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
1022 $domain = $this->resolveDomainID( $domain );
1023 $role = $this->getRoleFromIndex( $i );
1025 return new DBConnRef( $this, $this->getConnection( $i, $groups, $domain, $flags ), $role );
1028 public function getLazyConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
1029 $domain = $this->resolveDomainID( $domain );
1030 $role = $this->getRoleFromIndex( $i );
1032 return new DBConnRef( $this, [ $i, $groups, $domain, $flags ], $role );
1035 public function getMaintenanceConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ) {
1036 $domain = $this->resolveDomainID( $domain );
1037 $role = $this->getRoleFromIndex( $i );
1039 return new MaintainableDBConnRef(
1040 $this, $this->getConnection( $i, $groups, $domain, $flags ), $role );
1044 * @param int $i Server index or DB_MASTER/DB_REPLICA
1045 * @return int One of DB_MASTER/DB_REPLICA
1047 private function getRoleFromIndex( $i ) {
1048 return ( $i === self
::DB_MASTER ||
$i === $this->getWriterIndex() )
1055 * @param string|bool $domain
1057 * @return Database|bool Live database handle or false on failure
1058 * @deprecated Since 1.34 Use getConnection() instead
1060 public function openConnection( $i, $domain = false, $flags = 0 ) {
1061 return $this->getConnection( $i, [], $domain, $flags | self
::CONN_SILENCE_ERRORS
);
1065 * Open a connection to a local DB, or return one if it is already open.
1067 * On error, returns false, and the connection which caused the
1068 * error will be available via $this->errorConnection.
1070 * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
1072 * @param int $i Server index
1073 * @param int $flags Class CONN_* constant bitfield
1075 * @throws InvalidArgumentException When the server index is invalid
1076 * @throws UnexpectedValueException When the DB domain of the connection is corrupted
1078 private function getLocalConnection( $i, $flags = 0 ) {
1079 // Connection handles required to be in auto-commit mode use a separate connection
1080 // pool since the main pool is effected by implicit and explicit transaction rounds
1081 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
1083 $connKey = $autoCommit ? self
::KEY_LOCAL_NOROUND
: self
::KEY_LOCAL
;
1084 if ( isset( $this->conns
[$connKey][$i][0] ) ) {
1085 $conn = $this->conns
[$connKey][$i][0];
1087 // Open a new connection
1088 $server = $this->getServerInfoStrict( $i );
1089 $server['serverIndex'] = $i;
1090 $server['autoCommitOnly'] = $autoCommit;
1091 $conn = $this->reallyOpenConnection( $server, $this->localDomain
);
1092 $host = $this->getServerName( $i );
1093 if ( $conn->isOpen() ) {
1094 $this->connLogger
->debug(
1095 __METHOD__
. ": connected to database $i at '$host'." );
1096 $this->conns
[$connKey][$i][0] = $conn;
1098 $this->connLogger
->warning(
1099 __METHOD__
. ": failed to connect to database $i at '$host'." );
1100 $this->errorConnection
= $conn;
1105 // Final sanity check to make sure the right domain is selected
1107 $conn instanceof IDatabase
&&
1108 !$this->localDomain
->isCompatible( $conn->getDomainID() )
1110 throw new UnexpectedValueException(
1111 "Got connection to '{$conn->getDomainID()}', " .
1112 "but expected local domain ('{$this->localDomain}')" );
1119 * Open a connection to a foreign DB, or return one if it is already open.
1121 * Increments a reference count on the returned connection which locks the
1122 * connection to the requested domain. This reference count can be
1123 * decremented by calling reuseConnection().
1125 * If a connection is open to the appropriate server already, but with the wrong
1126 * database, it will be switched to the right database and returned, as long as
1127 * it has been freed first with reuseConnection().
1129 * On error, returns false, and the connection which caused the
1130 * error will be available via $this->errorConnection.
1132 * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
1134 * @param int $i Server index
1135 * @param string $domain Domain ID to open
1136 * @param int $flags Class CONN_* constant bitfield
1137 * @return Database|bool Returns false on connection error
1138 * @throws DBError When database selection fails
1139 * @throws InvalidArgumentException When the server index is invalid
1140 * @throws UnexpectedValueException When the DB domain of the connection is corrupted
1142 private function getForeignConnection( $i, $domain, $flags = 0 ) {
1143 $domainInstance = DatabaseDomain
::newFromId( $domain );
1144 // Connection handles required to be in auto-commit mode use a separate connection
1145 // pool since the main pool is effected by implicit and explicit transaction rounds
1146 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
1148 if ( $autoCommit ) {
1149 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
1150 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
1152 $connFreeKey = self
::KEY_FOREIGN_FREE
;
1153 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
1156 /** @var Database $conn */
1159 if ( isset( $this->conns
[$connInUseKey][$i][$domain] ) ) {
1160 // Reuse an in-use connection for the same domain
1161 $conn = $this->conns
[$connInUseKey][$i][$domain];
1162 $this->connLogger
->debug( __METHOD__
. ": reusing connection $i/$domain" );
1163 } elseif ( isset( $this->conns
[$connFreeKey][$i][$domain] ) ) {
1164 // Reuse a free connection for the same domain
1165 $conn = $this->conns
[$connFreeKey][$i][$domain];
1166 unset( $this->conns
[$connFreeKey][$i][$domain] );
1167 $this->conns
[$connInUseKey][$i][$domain] = $conn;
1168 $this->connLogger
->debug( __METHOD__
. ": reusing free connection $i/$domain" );
1169 } elseif ( !empty( $this->conns
[$connFreeKey][$i] ) ) {
1170 // Reuse a free connection from another domain if possible
1171 foreach ( $this->conns
[$connFreeKey][$i] as $oldDomain => $conn ) {
1172 if ( $domainInstance->getDatabase() !== null ) {
1173 // Check if changing the database will require a new connection.
1174 // In that case, leave the connection handle alone and keep looking.
1175 // This prevents connections from being closed mid-transaction and can
1176 // also avoid overhead if the same database will later be requested.
1178 $conn->databasesAreIndependent() &&
1179 $conn->getDBname() !== $domainInstance->getDatabase()
1183 // Select the new database, schema, and prefix
1184 $conn->selectDomain( $domainInstance );
1186 // Stay on the current database, but update the schema/prefix
1187 $conn->dbSchema( $domainInstance->getSchema() );
1188 $conn->tablePrefix( $domainInstance->getTablePrefix() );
1190 unset( $this->conns
[$connFreeKey][$i][$oldDomain] );
1191 // Note that if $domain is an empty string, getDomainID() might not match it
1192 $this->conns
[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1193 $this->connLogger
->debug( __METHOD__
.
1194 ": reusing free connection from $oldDomain for $domain" );
1200 // Open a new connection
1201 $server = $this->getServerInfoStrict( $i );
1202 $server['serverIndex'] = $i;
1203 $server['foreignPoolRefCount'] = 0;
1204 $server['foreign'] = true;
1205 $server['autoCommitOnly'] = $autoCommit;
1206 $conn = $this->reallyOpenConnection( $server, $domainInstance );
1207 if ( !$conn->isOpen() ) {
1208 $this->connLogger
->warning( __METHOD__
. ": connection error for $i/$domain" );
1209 $this->errorConnection
= $conn;
1212 // Note that if $domain is an empty string, getDomainID() might not match it
1213 $this->conns
[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1214 $this->connLogger
->debug( __METHOD__
. ": opened new connection for $i/$domain" );
1218 if ( $conn instanceof IDatabase
) {
1219 // Final sanity check to make sure the right domain is selected
1220 if ( !$domainInstance->isCompatible( $conn->getDomainID() ) ) {
1221 throw new UnexpectedValueException(
1222 "Got connection to '{$conn->getDomainID()}', but expected '$domain'" );
1224 // Increment reference count
1225 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
1226 $conn->setLBInfo( 'foreignPoolRefCount', $refCount +
1 );
1232 public function getServerAttributes( $i ) {
1233 return Database
::attributesFromType(
1234 $this->getServerType( $i ),
1235 $this->servers
[$i]['driver'] ??
null
1240 * Test if the specified index represents an open connection
1242 * @param int $index Server index
1245 private function isOpen( $index ) {
1246 return (bool)$this->getAnyOpenConnection( $index );
1250 * Open a new network connection to a server (uncached)
1252 * Returns a Database object whether or not the connection was successful.
1254 * @param array $server
1255 * @param DatabaseDomain $domain Domain the connection is for, possibly unspecified
1257 * @throws DBAccessError
1258 * @throws InvalidArgumentException
1260 protected function reallyOpenConnection( array $server, DatabaseDomain
$domain ) {
1261 if ( $this->disabled
) {
1262 throw new DBAccessError();
1265 if ( $domain->getDatabase() === null ) {
1266 // The database domain does not specify a DB name and some database systems require a
1267 // valid DB specified on connection. The $server configuration array contains a default
1268 // DB name to use for connections in such cases.
1269 if ( $server['type'] === 'mysql' ) {
1270 // For MySQL, DATABASE and SCHEMA are synonyms, connections need not specify a DB,
1271 // and the DB name in $server might not exist due to legacy reasons (the default
1272 // domain used to ignore the local LB domain, even when mismatched).
1273 $server['dbname'] = null;
1276 $server['dbname'] = $domain->getDatabase();
1279 if ( $domain->getSchema() !== null ) {
1280 $server['schema'] = $domain->getSchema();
1283 // It is always possible to connect with any prefix, even the empty string
1284 $server['tablePrefix'] = $domain->getTablePrefix();
1286 // Let the handle know what the cluster master is (e.g. "db1052")
1287 $masterName = $this->getServerName( $this->getWriterIndex() );
1288 $server['clusterMasterHost'] = $masterName;
1290 $server['srvCache'] = $this->srvCache
;
1291 // Set loggers and profilers
1292 $server['connLogger'] = $this->connLogger
;
1293 $server['queryLogger'] = $this->queryLogger
;
1294 $server['errorLogger'] = $this->errorLogger
;
1295 $server['deprecationLogger'] = $this->deprecationLogger
;
1296 $server['profiler'] = $this->profiler
;
1297 $server['trxProfiler'] = $this->trxProfiler
;
1298 // Use the same agent and PHP mode for all DB handles
1299 $server['cliMode'] = $this->cliMode
;
1300 $server['agent'] = $this->agent
;
1301 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
1302 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
1303 $server['flags'] = $server['flags'] ?? IDatabase
::DBO_DEFAULT
;
1305 // Create a live connection object
1306 $conn = Database
::factory( $server['type'], $server, Database
::NEW_UNCONNECTED
);
1307 $conn->setLBInfo( $server );
1308 $conn->setLazyMasterHandle(
1309 $this->getLazyConnectionRef( self
::DB_MASTER
, [], $conn->getDomainID() )
1311 $conn->setTableAliases( $this->tableAliases
);
1312 $conn->setIndexAliases( $this->indexAliases
);
1315 $conn->initConnection();
1316 ++
$this->connectionCounter
;
1317 } catch ( DBConnectionError
$e ) {
1318 // ignore; let the DB handle the logging
1321 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1322 if ( $this->trxRoundId
!== false ) {
1323 $this->applyTransactionRoundFlags( $conn );
1325 foreach ( $this->trxRecurringCallbacks
as $name => $callback ) {
1326 $conn->setTransactionListener( $name, $callback );
1330 $this->lazyLoadReplicationPositions(); // session consistency
1332 // Log when many connection are made on requests
1333 $count = $this->getCurrentConnectionCount();
1334 if ( $count >= self
::CONN_HELD_WARN_THRESHOLD
) {
1335 $this->perfLogger
->warning(
1336 __METHOD__
. ": {connections}+ connections made (master={masterdb})",
1338 'connections' => $count,
1339 'dbserver' => $conn->getServer(),
1340 'masterdb' => $conn->getLBInfo( 'clusterMasterHost' )
1349 * Make sure that any "waitForPos" positions are loaded and available to doWait()
1351 private function lazyLoadReplicationPositions() {
1352 if ( !$this->connectionAttempted
&& $this->chronologyCallback
) {
1353 $this->connectionAttempted
= true;
1354 ( $this->chronologyCallback
)( $this ); // generally calls waitFor()
1355 $this->connLogger
->debug( __METHOD__
. ': executed chronology callback.' );
1360 * @throws DBConnectionError
1362 private function reportConnectionError() {
1363 $conn = $this->errorConnection
; // the connection which caused the error
1365 'method' => __METHOD__
,
1366 'last_error' => $this->lastError
,
1369 if ( $conn instanceof IDatabase
) {
1370 $context['db_server'] = $conn->getServer();
1371 $this->connLogger
->warning(
1372 __METHOD__
. ": connection error: {last_error} ({db_server})",
1376 throw new DBConnectionError( $conn, "{$this->lastError} ({$context['db_server']})" );
1378 // No last connection, probably due to all servers being too busy
1379 $this->connLogger
->error(
1381 ": LB failure with no last connection. Connection error: {last_error}",
1385 // If all servers were busy, "lastError" will contain something sensible
1386 throw new DBConnectionError( null, $this->lastError
);
1390 public function getWriterIndex() {
1395 * Returns true if the specified index is a valid server index
1399 * @deprecated Since 1.34
1401 public function haveIndex( $i ) {
1402 return array_key_exists( $i, $this->servers
);
1406 * Returns true if the specified index is valid and has non-zero load
1410 * @deprecated Since 1.34
1412 public function isNonZeroLoad( $i ) {
1413 return ( isset( $this->servers
[$i] ) && $this->groupLoads
[self
::GROUP_GENERIC
][$i] > 0 );
1416 public function getServerCount() {
1417 return count( $this->servers
);
1420 public function hasReplicaServers() {
1421 return ( $this->getServerCount() > 1 );
1424 public function hasStreamingReplicaServers() {
1425 foreach ( $this->servers
as $i => $server ) {
1426 if ( $i !== $this->getWriterIndex() && empty( $server['is static'] ) ) {
1434 public function getServerName( $i ) {
1435 $name = $this->servers
[$i]['hostName'] ??
( $this->servers
[$i]['host'] ??
'' );
1437 return ( $name != '' ) ?
$name : 'localhost';
1440 public function getServerInfo( $i ) {
1441 return $this->servers
[$i] ??
false;
1444 public function getServerType( $i ) {
1445 return $this->servers
[$i]['type'] ??
'unknown';
1448 public function getMasterPos() {
1449 $index = $this->getWriterIndex();
1451 $conn = $this->getAnyOpenConnection( $index );
1453 return $conn->getMasterPos();
1456 $conn = $this->getConnection( $index, self
::CONN_SILENCE_ERRORS
);
1458 $this->reportConnectionError();
1459 return null; // unreachable due to exception
1463 $pos = $conn->getMasterPos();
1465 $this->closeConnection( $conn );
1471 public function getReplicaResumePos() {
1472 // Get the position of any existing master server connection
1473 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1474 if ( $masterConn ) {
1475 return $masterConn->getMasterPos();
1478 // Get the highest position of any existing replica server connection
1479 $highestPos = false;
1480 $serverCount = $this->getServerCount();
1481 for ( $i = 1; $i < $serverCount; $i++
) {
1482 if ( !empty( $this->servers
[$i]['is static'] ) ) {
1483 continue; // server does not use replication
1486 $conn = $this->getAnyOpenConnection( $i );
1487 $pos = $conn ?
$conn->getReplicaPos() : false;
1489 continue; // no open connection or could not get position
1492 $highestPos = $highestPos ?
: $pos;
1493 if ( $pos->hasReached( $highestPos ) ) {
1501 public function disable() {
1503 $this->disabled
= true;
1506 public function closeAll() {
1507 if ( $this->ownerId
=== null ) {
1508 /** @noinspection PhpUnusedLocalVariableInspection */
1509 $scope = ScopedCallback
::newScopedIgnoreUserAbort();
1512 $fname = __METHOD__
;
1513 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( $fname ) {
1514 $host = $conn->getServer();
1515 $this->connLogger
->debug(
1516 $fname . ": closing connection to database '$host'." );
1520 $this->conns
= self
::newTrackedConnectionsArray();
1523 public function closeConnection( IDatabase
$conn ) {
1524 if ( $conn instanceof DBConnRef
) {
1525 // Avoid calling close() but still leaving the handle in the pool
1526 throw new RuntimeException( 'Cannot close DBConnRef instance; it must be shareable' );
1529 $serverIndex = $conn->getLBInfo( 'serverIndex' );
1530 foreach ( $this->conns
as $type => $connsByServer ) {
1531 if ( !isset( $connsByServer[$serverIndex] ) ) {
1535 foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1536 if ( $conn === $trackedConn ) {
1537 $host = $this->getServerName( $i );
1538 $this->connLogger
->debug(
1539 __METHOD__
. ": closing connection to database $i at '$host'." );
1540 unset( $this->conns
[$type][$serverIndex][$i] );
1549 public function commitAll( $fname = __METHOD__
, $owner = null ) {
1550 $this->commitMasterChanges( $fname, $owner );
1551 $this->flushMasterSnapshots( $fname );
1552 $this->flushReplicaSnapshots( $fname );
1555 public function finalizeMasterChanges( $fname = __METHOD__
, $owner = null ) {
1556 $this->assertOwnership( $fname, $owner );
1557 $this->assertTransactionRoundStage( [ self
::ROUND_CURSORY
, self
::ROUND_FINALIZED
] );
1558 if ( $this->ownerId
=== null ) {
1559 /** @noinspection PhpUnusedLocalVariableInspection */
1560 $scope = ScopedCallback
::newScopedIgnoreUserAbort();
1563 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1564 // Loop until callbacks stop adding callbacks on other connections
1567 $count = 0; // callbacks execution attempts
1568 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( &$count ) {
1569 // Run any pre-commit callbacks while leaving the post-commit ones suppressed.
1570 // Any error should cause all (peer) transactions to be rolled back together.
1571 $count +
= $conn->runOnTransactionPreCommitCallbacks();
1574 } while ( $count > 0 );
1575 // Defer post-commit callbacks until after COMMIT/ROLLBACK happens on all handles
1576 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1577 $conn->setTrxEndCallbackSuppression( true );
1579 $this->trxRoundStage
= self
::ROUND_FINALIZED
;
1584 public function approveMasterChanges( array $options, $fname = __METHOD__
, $owner = null ) {
1585 $this->assertOwnership( $fname, $owner );
1586 $this->assertTransactionRoundStage( self
::ROUND_FINALIZED
);
1587 if ( $this->ownerId
=== null ) {
1588 /** @noinspection PhpUnusedLocalVariableInspection */
1589 $scope = ScopedCallback
::newScopedIgnoreUserAbort();
1592 $limit = $options['maxWriteDuration'] ??
0;
1594 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1595 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $limit ) {
1596 // If atomic sections or explicit transactions are still open, some caller must have
1597 // caught an exception but failed to properly rollback any changes. Detect that and
1598 // throw and error (causing rollback).
1599 $conn->assertNoOpenTransactions();
1600 // Assert that the time to replicate the transaction will be sane.
1601 // If this fails, then all DB transactions will be rollback back together.
1602 $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY
);
1603 if ( $limit > 0 && $time > $limit ) {
1604 throw new DBTransactionSizeError(
1606 "Transaction spent $time second(s) in writes, exceeding the limit of $limit",
1610 // If a connection sits idle while slow queries execute on another, that connection
1611 // may end up dropped before the commit round is reached. Ping servers to detect this.
1612 if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1613 throw new DBTransactionError(
1615 "A connection to the {$conn->getDBname()} database was lost before commit"
1619 $this->trxRoundStage
= self
::ROUND_APPROVED
;
1622 public function beginMasterChanges( $fname = __METHOD__
, $owner = null ) {
1623 $this->assertOwnership( $fname, $owner );
1624 if ( $this->trxRoundId
!== false ) {
1625 throw new DBTransactionError(
1627 "$fname: Transaction round '{$this->trxRoundId}' already started"
1630 $this->assertTransactionRoundStage( self
::ROUND_CURSORY
);
1631 if ( $this->ownerId
=== null ) {
1632 /** @noinspection PhpUnusedLocalVariableInspection */
1633 $scope = ScopedCallback
::newScopedIgnoreUserAbort();
1636 // Clear any empty transactions (no writes/callbacks) from the implicit round
1637 $this->flushMasterSnapshots( $fname );
1639 $this->trxRoundId
= $fname;
1640 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1641 // Mark applicable handles as participating in this explicit transaction round.
1642 // For each of these handles, any writes and callbacks will be tied to a single
1643 // transaction. The (peer) handles will reject begin()/commit() calls unless they
1644 // are part of an en masse commit or an en masse rollback.
1645 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1646 $this->applyTransactionRoundFlags( $conn );
1648 $this->trxRoundStage
= self
::ROUND_CURSORY
;
1651 public function commitMasterChanges( $fname = __METHOD__
, $owner = null ) {
1652 $this->assertOwnership( $fname, $owner );
1653 $this->assertTransactionRoundStage( self
::ROUND_APPROVED
);
1654 if ( $this->ownerId
=== null ) {
1655 /** @noinspection PhpUnusedLocalVariableInspection */
1656 $scope = ScopedCallback
::newScopedIgnoreUserAbort();
1661 $restore = ( $this->trxRoundId
!== false );
1662 $this->trxRoundId
= false;
1663 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1664 // Commit any writes and clear any snapshots as well (callbacks require AUTOCOMMIT).
1665 // Note that callbacks should already be suppressed due to finalizeMasterChanges().
1666 $this->forEachOpenMasterConnection(
1667 function ( IDatabase
$conn ) use ( $fname, &$failures ) {
1669 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1670 } catch ( DBError
$e ) {
1671 ( $this->errorLogger
)( $e );
1672 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1677 throw new DBTransactionError(
1679 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1683 // Unmark handles as participating in this explicit transaction round
1684 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1685 $this->undoTransactionRoundFlags( $conn );
1688 $this->trxRoundStage
= self
::ROUND_COMMIT_CALLBACKS
;
1691 public function runMasterTransactionIdleCallbacks( $fname = __METHOD__
, $owner = null ) {
1692 $this->assertOwnership( $fname, $owner );
1693 if ( $this->trxRoundStage
=== self
::ROUND_COMMIT_CALLBACKS
) {
1694 $type = IDatabase
::TRIGGER_COMMIT
;
1695 } elseif ( $this->trxRoundStage
=== self
::ROUND_ROLLBACK_CALLBACKS
) {
1696 $type = IDatabase
::TRIGGER_ROLLBACK
;
1698 throw new DBTransactionError(
1700 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1703 if ( $this->ownerId
=== null ) {
1704 /** @noinspection PhpUnusedLocalVariableInspection */
1705 $scope = ScopedCallback
::newScopedIgnoreUserAbort();
1708 $oldStage = $this->trxRoundStage
;
1709 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1711 // Now that the COMMIT/ROLLBACK step is over, enable post-commit callback runs
1712 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1713 $conn->setTrxEndCallbackSuppression( false );
1716 $e = null; // first exception
1717 $fname = __METHOD__
;
1718 // Loop until callbacks stop adding callbacks on other connections
1720 // Run any pending callbacks for each connection...
1721 $count = 0; // callback execution attempts
1722 $this->forEachOpenMasterConnection(
1723 function ( Database
$conn ) use ( $type, &$e, &$count ) {
1724 if ( $conn->trxLevel() ) {
1725 return; // retry in the next iteration, after commit() is called
1728 $count +
= $conn->runOnTransactionIdleCallbacks( $type );
1729 } catch ( Exception
$ex ) {
1734 // Clear out any active transactions left over from callbacks...
1735 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( &$e, $fname ) {
1736 if ( $conn->writesPending() ) {
1737 // A callback from another handle wrote to this one and DBO_TRX is set
1738 $this->queryLogger
->warning( $fname . ": found writes pending." );
1739 $fnames = implode( ', ', $conn->pendingWriteAndCallbackCallers() );
1740 $this->queryLogger
->warning(
1741 $fname . ": found writes pending ($fnames).",
1743 'db_server' => $conn->getServer(),
1744 'db_name' => $conn->getDBname()
1747 } elseif ( $conn->trxLevel() ) {
1748 // A callback from another handle read from this one and DBO_TRX is set,
1749 // which can easily happen if there is only one DB (no replicas)
1750 $this->queryLogger
->debug( $fname . ": found empty transaction." );
1753 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1754 } catch ( Exception
$ex ) {
1758 } while ( $count > 0 );
1760 $this->trxRoundStage
= $oldStage;
1765 public function runMasterTransactionListenerCallbacks( $fname = __METHOD__
, $owner = null ) {
1766 $this->assertOwnership( $fname, $owner );
1767 if ( $this->trxRoundStage
=== self
::ROUND_COMMIT_CALLBACKS
) {
1768 $type = IDatabase
::TRIGGER_COMMIT
;
1769 } elseif ( $this->trxRoundStage
=== self
::ROUND_ROLLBACK_CALLBACKS
) {
1770 $type = IDatabase
::TRIGGER_ROLLBACK
;
1772 throw new DBTransactionError(
1774 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1777 if ( $this->ownerId
=== null ) {
1778 /** @noinspection PhpUnusedLocalVariableInspection */
1779 $scope = ScopedCallback
::newScopedIgnoreUserAbort();
1784 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1785 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( $type, &$e ) {
1787 $conn->runTransactionListenerCallbacks( $type );
1788 } catch ( Exception
$ex ) {
1792 $this->trxRoundStage
= self
::ROUND_CURSORY
;
1797 public function rollbackMasterChanges( $fname = __METHOD__
, $owner = null ) {
1798 $this->assertOwnership( $fname, $owner );
1799 if ( $this->ownerId
=== null ) {
1800 /** @noinspection PhpUnusedLocalVariableInspection */
1801 $scope = ScopedCallback
::newScopedIgnoreUserAbort();
1804 $restore = ( $this->trxRoundId
!== false );
1805 $this->trxRoundId
= false;
1806 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1807 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $fname ) {
1808 $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS
);
1811 // Unmark handles as participating in this explicit transaction round
1812 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1813 $this->undoTransactionRoundFlags( $conn );
1816 $this->trxRoundStage
= self
::ROUND_ROLLBACK_CALLBACKS
;
1820 * @param string|string[] $stage
1821 * @throws DBTransactionError
1823 private function assertTransactionRoundStage( $stage ) {
1824 $stages = (array)$stage;
1826 if ( !in_array( $this->trxRoundStage
, $stages, true ) ) {
1827 $stageList = implode(
1829 array_map( function ( $v ) {
1833 throw new DBTransactionError(
1835 "Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
1841 * @param string $fname
1842 * @param int|null $owner Owner ID of the caller
1843 * @throws DBTransactionError
1845 private function assertOwnership( $fname, $owner ) {
1846 if ( $this->ownerId
!== null && $owner !== $this->ownerId
) {
1847 throw new DBTransactionError(
1849 "$fname: LoadBalancer is owned by LBFactory #{$this->ownerId} (got '$owner')."
1855 * Make all DB servers with DBO_DEFAULT/DBO_TRX set join the transaction round
1857 * Some servers may have neither flag enabled, meaning that they opt out of such
1858 * transaction rounds and remain in auto-commit mode. Such behavior might be desired
1859 * when a DB server is used for something like simple key/value storage.
1861 * @param Database $conn
1863 private function applyTransactionRoundFlags( Database
$conn ) {
1864 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1865 return; // transaction rounds do not apply to these connections
1868 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1869 // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1870 // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1871 $conn->setFlag( $conn::DBO_TRX
, $conn::REMEMBER_PRIOR
);
1874 if ( $conn->getFlag( $conn::DBO_TRX
) ) {
1875 $conn->setLBInfo( 'trxRoundId', $this->trxRoundId
);
1880 * @param Database $conn
1882 private function undoTransactionRoundFlags( Database
$conn ) {
1883 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1884 return; // transaction rounds do not apply to these connections
1887 if ( $conn->getFlag( $conn::DBO_TRX
) ) {
1888 $conn->setLBInfo( 'trxRoundId', null ); // remove the round ID
1891 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1892 $conn->restoreFlags( $conn::RESTORE_PRIOR
);
1896 public function flushReplicaSnapshots( $fname = __METHOD__
) {
1897 $this->forEachOpenReplicaConnection( function ( IDatabase
$conn ) use ( $fname ) {
1898 $conn->flushSnapshot( $fname );
1902 public function flushMasterSnapshots( $fname = __METHOD__
) {
1903 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $fname ) {
1904 $conn->flushSnapshot( $fname );
1912 public function getTransactionRoundStage() {
1913 return $this->trxRoundStage
;
1916 public function hasMasterConnection() {
1917 return $this->isOpen( $this->getWriterIndex() );
1920 public function hasMasterChanges() {
1922 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$pending ) {
1923 $pending |
= $conn->writesOrCallbacksPending();
1926 return (bool)$pending;
1929 public function lastMasterChangeTimestamp() {
1931 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$lastTime ) {
1932 $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1938 public function hasOrMadeRecentMasterChanges( $age = null ) {
1939 $age = ( $age === null ) ?
$this->waitTimeout
: $age;
1941 return ( $this->hasMasterChanges()
1942 ||
$this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1945 public function pendingMasterChangeCallers() {
1947 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$fnames ) {
1948 $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1954 public function getLaggedReplicaMode( $domain = false ) {
1955 if ( $this->laggedReplicaMode
) {
1956 return true; // stay in lagged replica mode
1959 if ( $this->hasStreamingReplicaServers() ) {
1960 // This will set "laggedReplicaMode" as needed
1961 $this->getReaderIndex( self
::GROUP_GENERIC
, $domain );
1964 return $this->laggedReplicaMode
;
1967 public function laggedReplicaUsed() {
1968 return $this->laggedReplicaMode
;
1971 public function getReadOnlyReason( $domain = false ) {
1972 $domainInstance = DatabaseDomain
::newFromId( $this->resolveDomainID( $domain ) );
1974 if ( $this->readOnlyReason
!== false ) {
1975 return $this->readOnlyReason
;
1976 } elseif ( $this->isMasterRunningReadOnly( $domainInstance ) ) {
1977 return 'The master database server is running in read-only mode.';
1978 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1979 return ( $this->getExistingReaderIndex( self
::GROUP_GENERIC
) >= 0 )
1980 ?
'The database is read-only until replication lag decreases.'
1981 : 'The database is read-only until a replica database server becomes reachable.';
1988 * @param IDatabase $conn Master connection
1989 * @param int $flags Bitfield of class CONN_* constants
1990 * @return bool Whether the entire server or currently selected DB/schema is read-only
1992 private function isMasterConnectionReadOnly( IDatabase
$conn, $flags = 0 ) {
1993 // Note that table prefixes are not related to server-side read-only mode
1994 $key = $this->srvCache
->makeGlobalKey(
1995 'rdbms-server-readonly',
2001 if ( ( $flags & self
::CONN_REFRESH_READ_ONLY
) == self
::CONN_REFRESH_READ_ONLY
) {
2003 $readOnly = (int)$conn->serverIsReadOnly();
2004 } catch ( DBError
$e ) {
2007 $this->srvCache
->set( $key, $readOnly, BagOStuff
::TTL_PROC_SHORT
);
2009 $readOnly = $this->srvCache
->getWithSetCallback(
2011 BagOStuff
::TTL_PROC_SHORT
,
2012 function () use ( $conn ) {
2014 return (int)$conn->serverIsReadOnly();
2015 } catch ( DBError
$e ) {
2022 return (bool)$readOnly;
2026 * @param DatabaseDomain $domain
2027 * @return bool Whether the entire master server or the local domain DB is read-only
2029 private function isMasterRunningReadOnly( DatabaseDomain
$domain ) {
2030 // Context will often be HTTP GET/HEAD; heavily cache the results
2031 return (bool)$this->wanCache
->getWithSetCallback(
2032 // Note that table prefixes are not related to server-side read-only mode
2033 $this->wanCache
->makeGlobalKey(
2034 'rdbms-server-readonly',
2035 $this->getMasterServerName(),
2036 $domain->getDatabase(),
2037 $domain->getSchema()
2039 self
::TTL_CACHE_READONLY
,
2040 function () use ( $domain ) {
2041 $old = $this->trxProfiler
->setSilenced( true );
2043 $index = $this->getWriterIndex();
2044 // Reset the cache for isMasterConnectionReadOnly()
2045 $flags = self
::CONN_REFRESH_READ_ONLY
;
2046 $conn = $this->getServerConnection( $index, $domain->getId(), $flags );
2047 // Reuse the process cache set above
2048 $readOnly = (int)$this->isMasterConnectionReadOnly( $conn );
2049 $this->reuseConnection( $conn );
2050 } catch ( DBError
$e ) {
2053 $this->trxProfiler
->setSilenced( $old );
2057 [ 'pcTTL' => WANObjectCache
::TTL_PROC_LONG
, 'lockTSE' => 10, 'busyValue' => 0 ]
2061 public function allowLagged( $mode = null ) {
2062 if ( $mode === null ) {
2063 return $this->allowLagged
;
2065 $this->allowLagged
= $mode;
2067 return $this->allowLagged
;
2070 public function pingAll() {
2072 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$success ) {
2073 if ( !$conn->ping() ) {
2081 public function forEachOpenConnection( $callback, array $params = [] ) {
2082 foreach ( $this->conns
as $connsByServer ) {
2083 foreach ( $connsByServer as $serverConns ) {
2084 foreach ( $serverConns as $conn ) {
2085 $callback( $conn, ...$params );
2091 public function forEachOpenMasterConnection( $callback, array $params = [] ) {
2092 $masterIndex = $this->getWriterIndex();
2093 foreach ( $this->conns
as $connsByServer ) {
2094 if ( isset( $connsByServer[$masterIndex] ) ) {
2095 /** @var IDatabase $conn */
2096 foreach ( $connsByServer[$masterIndex] as $conn ) {
2097 $callback( $conn, ...$params );
2103 public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
2104 foreach ( $this->conns
as $connsByServer ) {
2105 foreach ( $connsByServer as $i => $serverConns ) {
2106 if ( $i === $this->getWriterIndex() ) {
2107 continue; // skip master
2109 foreach ( $serverConns as $conn ) {
2110 $callback( $conn, ...$params );
2119 private function getCurrentConnectionCount() {
2121 foreach ( $this->conns
as $connsByServer ) {
2122 foreach ( $connsByServer as $serverConns ) {
2123 $count +
= count( $serverConns );
2130 public function getMaxLag( $domain = false ) {
2135 if ( $this->hasReplicaServers() ) {
2136 $lagTimes = $this->getLagTimes( $domain );
2137 foreach ( $lagTimes as $i => $lag ) {
2138 if ( $this->groupLoads
[self
::GROUP_GENERIC
][$i] > 0 && $lag > $maxLag ) {
2140 $host = $this->getServerInfoStrict( $i, 'host' );
2146 return [ $host, $maxLag, $maxIndex ];
2149 public function getLagTimes( $domain = false ) {
2150 if ( !$this->hasReplicaServers() ) {
2151 return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
2154 $knownLagTimes = []; // map of (server index => 0 seconds)
2155 $indexesWithLag = [];
2156 foreach ( $this->servers
as $i => $server ) {
2157 if ( empty( $server['is static'] ) ) {
2158 $indexesWithLag[] = $i; // DB server might have replication lag
2160 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
2164 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) +
$knownLagTimes;
2168 * Get the lag in seconds for a given connection, or zero if this load
2169 * balancer does not have replication enabled.
2171 * This should be used in preference to Database::getLag() in cases where
2172 * replication may not be in use, since there is no way to determine if
2173 * replication is in use at the connection level without running
2174 * potentially restricted queries such as SHOW SLAVE STATUS. Using this
2175 * function instead of Database::getLag() avoids a fatal error in this
2176 * case on many installations.
2178 * @param IDatabase $conn
2179 * @return int|bool Returns false on error
2180 * @deprecated Since 1.34 Use IDatabase::getLag() instead
2182 public function safeGetLag( IDatabase
$conn ) {
2183 if ( $conn->getLBInfo( 'is static' ) ) {
2184 return 0; // static dataset
2185 } elseif ( $conn->getLBInfo( 'serverIndex' ) == $this->getWriterIndex() ) {
2186 return 0; // this is the master
2189 return $conn->getLag();
2192 public function waitForMasterPos( IDatabase
$conn, $pos = false, $timeout = null ) {
2193 $timeout = max( 1, $timeout ?
: $this->waitTimeout
);
2195 if ( $this->getServerCount() <= 1 ||
!$conn->getLBInfo( 'replica' ) ) {
2196 return true; // server is not a replica DB
2200 // Get the current master position, opening a connection if needed
2201 $index = $this->getWriterIndex();
2202 $flags = self
::CONN_SILENCE_ERRORS
;
2203 $masterConn = $this->getAnyOpenConnection( $index, $flags );
2204 if ( $masterConn ) {
2205 $pos = $masterConn->getMasterPos();
2207 $masterConn = $this->getServerConnection( $index, self
::DOMAIN_ANY
, $flags );
2208 if ( !$masterConn ) {
2209 throw new DBReplicationWaitError(
2211 "Could not obtain a master database connection to get the position"
2214 $pos = $masterConn->getMasterPos();
2215 $this->closeConnection( $masterConn );
2219 if ( $pos instanceof DBMasterPos
) {
2220 $start = microtime( true );
2221 $result = $conn->masterPosWait( $pos, $timeout );
2222 $seconds = max( microtime( true ) - $start, 0 );
2223 if ( $result == -1 ||
is_null( $result ) ) {
2224 $msg = __METHOD__
. ': timed out waiting on {host} pos {pos} [{seconds}s]';
2225 $this->replLogger
->warning( $msg, [
2226 'host' => $conn->getServer(),
2228 'seconds' => round( $seconds, 6 ),
2229 'trace' => ( new RuntimeException() )->getTraceAsString()
2233 $this->replLogger
->debug( __METHOD__
. ': done waiting' );
2237 $ok = false; // something is misconfigured
2238 $this->replLogger
->error(
2239 __METHOD__
. ': could not get master pos for {host}',
2241 'host' => $conn->getServer(),
2242 'trace' => ( new RuntimeException() )->getTraceAsString()
2251 * Wait for a replica DB to reach a specified master position
2253 * This will connect to the master to get an accurate position if $pos is not given
2255 * @param IDatabase $conn Replica DB
2256 * @param DBMasterPos|bool $pos Master position; default: current position
2257 * @param int $timeout Timeout in seconds [optional]
2258 * @return bool Success
2260 * @deprecated Since 1.34 Use waitForMasterPos() instead
2262 public function safeWaitForMasterPos( IDatabase
$conn, $pos = false, $timeout = null ) {
2263 return $this->waitForMasterPos( $conn, $pos, $timeout );
2266 public function setTransactionListener( $name, callable
$callback = null ) {
2268 $this->trxRecurringCallbacks
[$name] = $callback;
2270 unset( $this->trxRecurringCallbacks
[$name] );
2272 $this->forEachOpenMasterConnection(
2273 function ( IDatabase
$conn ) use ( $name, $callback ) {
2274 $conn->setTransactionListener( $name, $callback );
2279 public function setTableAliases( array $aliases ) {
2280 $this->tableAliases
= $aliases;
2283 public function setIndexAliases( array $aliases ) {
2284 $this->indexAliases
= $aliases;
2287 public function setLocalDomainPrefix( $prefix ) {
2288 // Find connections to explicit foreign domains still marked as in-use...
2290 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$domainsInUse ) {
2291 // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
2292 // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
2293 if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
2294 $domainsInUse[] = $conn->getDomainID();
2298 // Do not switch connections to explicit foreign domains unless marked as safe
2299 if ( $domainsInUse ) {
2300 $domains = implode( ', ', $domainsInUse );
2301 throw new DBUnexpectedError( null,
2302 "Foreign domain connections are still in use ($domains)" );
2305 $this->setLocalDomain( new DatabaseDomain(
2306 $this->localDomain
->getDatabase(),
2307 $this->localDomain
->getSchema(),
2311 // Update the prefix for all local connections...
2312 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( $prefix ) {
2313 if ( !$conn->getLBInfo( 'foreign' ) ) {
2314 $conn->tablePrefix( $prefix );
2319 public function redefineLocalDomain( $domain ) {
2322 $this->setLocalDomain( DatabaseDomain
::newFromId( $domain ) );
2325 public function setTempTablesOnlyMode( $value, $domain ) {
2326 $old = $this->tempTablesOnlyMode
[$domain] ??
false;
2328 $this->tempTablesOnlyMode
[$domain] = true;
2330 unset( $this->tempTablesOnlyMode
[$domain] );
2337 * @param DatabaseDomain $domain
2339 private function setLocalDomain( DatabaseDomain
$domain ) {
2340 $this->localDomain
= $domain;
2341 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
2342 // always true, gracefully handle the case when they fail to account for escaping.
2343 if ( $this->localDomain
->getTablePrefix() != '' ) {
2344 $this->localDomainIdAlias
=
2345 $this->localDomain
->getDatabase() . '-' . $this->localDomain
->getTablePrefix();
2347 $this->localDomainIdAlias
= $this->localDomain
->getDatabase();
2352 * @param int $i Server index
2353 * @param string|null $field Server index field [optional]
2354 * @return array|mixed
2355 * @throws InvalidArgumentException
2357 private function getServerInfoStrict( $i, $field = null ) {
2358 if ( !isset( $this->servers
[$i] ) ||
!is_array( $this->servers
[$i] ) ) {
2359 throw new InvalidArgumentException( "No server with index '$i'" );
2362 if ( $field !== null ) {
2363 if ( !array_key_exists( $field, $this->servers
[$i] ) ) {
2364 throw new InvalidArgumentException( "No field '$field' in server index '$i'" );
2367 return $this->servers
[$i][$field];
2370 return $this->servers
[$i];
2376 private function getMasterServerName() {
2377 return $this->getServerName( $this->getWriterIndex() );
2380 function __destruct() {
2381 // Avoid connection leaks for sanity
2387 * @deprecated since 1.29
2389 class_alias( LoadBalancer
::class, 'LoadBalancer' );