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
;
31 use InvalidArgumentException
;
36 * Database connection, tracking, load balancing, and transaction manager for a cluster
40 class LoadBalancer
implements ILoadBalancer
{
41 /** @var ILoadMonitor */
43 /** @var callable|null Callback to run before the first connection attempt */
44 private $chronologyCallback;
47 /** @var WANObjectCache */
49 /** @var object|string Class name or object With profileIn/profileOut methods */
51 /** @var TransactionProfiler */
53 /** @var LoggerInterface */
55 /** @var LoggerInterface */
57 /** @var LoggerInterface */
59 /** @var LoggerInterface */
61 /** @var callable Exception logger */
63 /** @var callable Deprecation logger */
64 private $deprecationLogger;
66 /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
69 /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
72 /** @var array[] Map of (server index => server config array) */
74 /** @var float[] Map of (server index => weight) */
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 ID string for the domain instead of DatabaseDomain::getId() */
85 private $localDomainIdAlias;
87 private $maxLag = self
::MAX_LAG_DEFAULT
;
89 /** @var string Current server name */
91 /** @var bool Whether this PHP instance is for a CLI script */
93 /** @var string Agent name for query profiling */
96 /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
97 private $tableAliases = [];
98 /** @var string[] Map of (index alias => index) */
99 private $indexAliases = [];
100 /** @var array[] Map of (name => callable) */
101 private $trxRecurringCallbacks = [];
103 /** @var Database DB connection object that caused a problem */
104 private $errorConnection;
105 /** @var int The generic (not query grouped) replica DB index (of $mServers) */
107 /** @var bool|DBMasterPos False if not set */
109 /** @var bool Whether the generic reader fell back to a lagged replica DB */
110 private $laggedReplicaMode = false;
111 /** @var bool Whether the generic reader fell back to a lagged replica DB */
112 private $allReplicasDownMode = false;
113 /** @var string The last DB selection or connection error */
114 private $lastError = 'Unknown error';
115 /** @var string|bool Reason the LB is read-only or false if not */
116 private $readOnlyReason = false;
117 /** @var int Total connections opened */
118 private $connsOpened = 0;
120 private $disabled = false;
121 /** @var bool Whether any connection has been attempted yet */
122 private $connectionAttempted = false;
124 /** @var string|bool String if a requested DBO_TRX transaction round is active */
125 private $trxRoundId = false;
126 /** @var string Stage of the current transaction round in the transaction round life-cycle */
127 private $trxRoundStage = self
::ROUND_CURSORY
;
129 /** @var string|null */
130 private $defaultGroup = null;
132 /** @var int Warn when this many connection are held */
133 const CONN_HELD_WARN_THRESHOLD
= 10;
135 /** @var int Default 'maxLag' when unspecified */
136 const MAX_LAG_DEFAULT
= 10;
137 /** @var int Default 'waitTimeout' when unspecified */
138 const MAX_WAIT_DEFAULT
= 10;
139 /** @var int Seconds to cache master server read-only status */
140 const TTL_CACHE_READONLY
= 5;
142 const KEY_LOCAL
= 'local';
143 const KEY_FOREIGN_FREE
= 'foreignFree';
144 const KEY_FOREIGN_INUSE
= 'foreignInUse';
146 const KEY_LOCAL_NOROUND
= 'localAutoCommit';
147 const KEY_FOREIGN_FREE_NOROUND
= 'foreignFreeAutoCommit';
148 const KEY_FOREIGN_INUSE_NOROUND
= 'foreignInUseAutoCommit';
150 /** @var string Transaction round, explicit or implicit, has not finished writing */
151 const ROUND_CURSORY
= 'cursory';
152 /** @var string Transaction round writes are complete and ready for pre-commit checks */
153 const ROUND_FINALIZED
= 'finalized';
154 /** @var string Transaction round passed final pre-commit checks */
155 const ROUND_APPROVED
= 'approved';
156 /** @var string Transaction round was committed and post-commit callbacks must be run */
157 const ROUND_COMMIT_CALLBACKS
= 'commit-callbacks';
158 /** @var string Transaction round was rolled back and post-rollback callbacks must be run */
159 const ROUND_ROLLBACK_CALLBACKS
= 'rollback-callbacks';
160 /** @var string Transaction round encountered an error */
161 const ROUND_ERROR
= 'error';
163 public function __construct( array $params ) {
164 if ( !isset( $params['servers'] ) ) {
165 throw new InvalidArgumentException( __CLASS__
. ': missing servers parameter' );
167 $this->servers
= $params['servers'];
168 foreach ( $this->servers
as $i => $server ) {
170 $this->servers
[$i]['master'] = true;
172 $this->servers
[$i]['replica'] = true;
176 $localDomain = isset( $params['localDomain'] )
177 ? DatabaseDomain
::newFromId( $params['localDomain'] )
178 : DatabaseDomain
::newUnspecified();
179 $this->setLocalDomain( $localDomain );
181 $this->waitTimeout
= $params['waitTimeout'] ?? self
::MAX_WAIT_DEFAULT
;
183 $this->readIndex
= -1;
185 // Connection were transaction rounds may be applied
186 self
::KEY_LOCAL
=> [],
187 self
::KEY_FOREIGN_INUSE
=> [],
188 self
::KEY_FOREIGN_FREE
=> [],
189 // Auto-committing counterpart connections that ignore transaction rounds
190 self
::KEY_LOCAL_NOROUND
=> [],
191 self
::KEY_FOREIGN_INUSE_NOROUND
=> [],
192 self
::KEY_FOREIGN_FREE_NOROUND
=> []
195 $this->waitForPos
= false;
196 $this->allowLagged
= false;
198 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
199 $this->readOnlyReason
= $params['readOnlyReason'];
202 if ( isset( $params['maxLag'] ) ) {
203 $this->maxLag
= $params['maxLag'];
206 if ( isset( $params['loadMonitor'] ) ) {
207 $this->loadMonitorConfig
= $params['loadMonitor'];
209 $this->loadMonitorConfig
= [ 'class' => 'LoadMonitorNull' ];
211 $this->loadMonitorConfig +
= [ 'lagWarnThreshold' => $this->maxLag
];
213 foreach ( $params['servers'] as $i => $server ) {
214 $this->loads
[$i] = $server['load'];
215 if ( isset( $server['groupLoads'] ) ) {
216 foreach ( $server['groupLoads'] as $group => $ratio ) {
217 if ( !isset( $this->groupLoads
[$group] ) ) {
218 $this->groupLoads
[$group] = [];
220 $this->groupLoads
[$group][$i] = $ratio;
225 if ( isset( $params['srvCache'] ) ) {
226 $this->srvCache
= $params['srvCache'];
228 $this->srvCache
= new EmptyBagOStuff();
230 if ( isset( $params['wanCache'] ) ) {
231 $this->wanCache
= $params['wanCache'];
233 $this->wanCache
= WANObjectCache
::newEmpty();
235 $this->profiler
= $params['profiler'] ??
null;
236 if ( isset( $params['trxProfiler'] ) ) {
237 $this->trxProfiler
= $params['trxProfiler'];
239 $this->trxProfiler
= new TransactionProfiler();
242 $this->errorLogger
= $params['errorLogger'] ??
function ( Exception
$e ) {
243 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING
);
245 $this->deprecationLogger
= $params['deprecationLogger'] ??
function ( $msg ) {
246 trigger_error( $msg, E_USER_DEPRECATED
);
249 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
250 $this->$key = $params[$key] ??
new NullLogger();
253 $this->hostname
= $params['hostname'] ??
( gethostname() ?
: 'unknown' );
254 $this->cliMode
= $params['cliMode'] ??
( PHP_SAPI
=== 'cli' || PHP_SAPI
=== 'phpdbg' );
255 $this->agent
= $params['agent'] ??
'';
257 if ( isset( $params['chronologyCallback'] ) ) {
258 $this->chronologyCallback
= $params['chronologyCallback'];
261 if ( isset( $params['roundStage'] ) ) {
262 if ( $params['roundStage'] === self
::STAGE_POSTCOMMIT_CALLBACKS
) {
263 $this->trxRoundStage
= self
::ROUND_COMMIT_CALLBACKS
;
264 } elseif ( $params['roundStage'] === self
::STAGE_POSTROLLBACK_CALLBACKS
) {
265 $this->trxRoundStage
= self
::ROUND_ROLLBACK_CALLBACKS
;
269 $this->defaultGroup
= $params['defaultGroup'] ??
null;
272 public function getLocalDomainID() {
273 return $this->localDomain
->getId();
276 public function resolveDomainID( $domain ) {
277 return ( $domain !== false ) ?
(string)$domain : $this->getLocalDomainID();
281 * Get a LoadMonitor instance
283 * @return ILoadMonitor
285 private function getLoadMonitor() {
286 if ( !isset( $this->loadMonitor
) ) {
288 'LoadMonitor' => LoadMonitor
::class,
289 'LoadMonitorNull' => LoadMonitorNull
::class,
290 'LoadMonitorMySQL' => LoadMonitorMySQL
::class,
293 $class = $this->loadMonitorConfig
['class'];
294 if ( isset( $compat[$class] ) ) {
295 $class = $compat[$class];
298 $this->loadMonitor
= new $class(
299 $this, $this->srvCache
, $this->wanCache
, $this->loadMonitorConfig
);
300 $this->loadMonitor
->setLogger( $this->replLogger
);
303 return $this->loadMonitor
;
307 * @param array $loads
308 * @param bool|string $domain Domain to get non-lagged for
309 * @param int $maxLag Restrict the maximum allowed lag to this many seconds
310 * @return bool|int|string
312 private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF
) {
313 $lags = $this->getLagTimes( $domain );
315 # Unset excessively lagged servers
316 foreach ( $lags as $i => $lag ) {
318 # How much lag this server nominally is allowed to have
319 $maxServerLag = $this->servers
[$i]['max lag'] ??
$this->maxLag
; // default
320 # Constrain that futher by $maxLag argument
321 $maxServerLag = min( $maxServerLag, $maxLag );
323 $host = $this->getServerName( $i );
324 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
325 $this->replLogger
->error(
327 ": server {host} is not replicating?", [ 'host' => $host ] );
329 } elseif ( $lag > $maxServerLag ) {
330 $this->replLogger
->info(
332 ": server {host} has {lag} seconds of lag (>= {maxlag})",
333 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
340 # Find out if all the replica DBs with non-zero load are lagged
342 foreach ( $loads as $load ) {
346 # No appropriate DB servers except maybe the master and some replica DBs with zero load
347 # Do NOT use the master
348 # Instead, this function will return false, triggering read-only mode,
349 # and a lagged replica DB will be used instead.
353 if ( count( $loads ) == 0 ) {
357 # Return a random representative of the remainder
358 return ArrayUtils
::pickRandom( $loads );
361 public function getReaderIndex( $group = false, $domain = false ) {
362 if ( count( $this->servers
) == 1 ) {
363 // Skip the load balancing if there's only one server
364 return $this->getWriterIndex();
365 } elseif ( $group === false && $this->readIndex
>= 0 ) {
366 // Shortcut if the generic reader index was already cached
367 return $this->readIndex
;
370 if ( $group !== false ) {
371 // Use the server weight array for this load group
372 if ( isset( $this->groupLoads
[$group] ) ) {
373 $loads = $this->groupLoads
[$group];
375 // No loads for this group, return false and the caller can use some other group
376 $this->connLogger
->info( __METHOD__
. ": no loads for group $group" );
381 // Use the generic load group
382 $loads = $this->loads
;
385 // Scale the configured load ratios according to each server's load and state
386 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
388 // Pick a server to use, accounting for weights, load, lag, and "waitForPos"
389 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
390 if ( $i === false ) {
391 // Replica DB connection unsuccessful
395 if ( $this->waitForPos
&& $i != $this->getWriterIndex() ) {
396 // Before any data queries are run, wait for the server to catch up to the
397 // specified position. This is used to improve session consistency. Note that
398 // when LoadBalancer::waitFor() sets "waitForPos", the waiting triggers here,
399 // so update laggedReplicaMode as needed for consistency.
400 if ( !$this->doWait( $i ) ) {
401 $laggedReplicaMode = true;
405 if ( $this->readIndex
<= 0 && $this->loads
[$i] > 0 && $group === false ) {
406 // Cache the generic reader index for future ungrouped DB_REPLICA handles
407 $this->readIndex
= $i;
408 // Record if the generic reader index is in "lagged replica DB" mode
409 if ( $laggedReplicaMode ) {
410 $this->laggedReplicaMode
= true;
414 $serverName = $this->getServerName( $i );
415 $this->connLogger
->debug( __METHOD__
. ": using server $serverName for group '$group'" );
421 * @param array $loads List of server weights
422 * @param string|bool $domain
423 * @return array (reader index, lagged replica mode) or false on failure
425 private function pickReaderIndex( array $loads, $domain = false ) {
426 if ( !count( $loads ) ) {
427 throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
430 /** @var int|bool $i Index of selected server */
432 /** @var bool $laggedReplicaMode Whether server is considered lagged */
433 $laggedReplicaMode = false;
435 // Quickly look through the available servers for a server that meets criteria...
436 $currentLoads = $loads;
437 while ( count( $currentLoads ) ) {
438 if ( $this->allowLagged ||
$laggedReplicaMode ) {
439 $i = ArrayUtils
::pickRandom( $currentLoads );
442 if ( $this->waitForPos
&& $this->waitForPos
->asOfTime() ) {
443 // "chronologyCallback" sets "waitForPos" for session consistency.
444 // This triggers doWait() after connect, so it's especially good to
445 // avoid lagged servers so as to avoid excessive delay in that method.
446 $ago = microtime( true ) - $this->waitForPos
->asOfTime();
447 // Aim for <= 1 second of waiting (being too picky can backfire)
448 $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago +
1 );
450 if ( $i === false ) {
451 // Any server with less lag than it's 'max lag' param is preferable
452 $i = $this->getRandomNonLagged( $currentLoads, $domain );
454 if ( $i === false && count( $currentLoads ) != 0 ) {
455 // All replica DBs lagged. Switch to read-only mode
456 $this->replLogger
->error(
457 __METHOD__
. ": all replica DBs lagged. Switch to read-only mode" );
458 $i = ArrayUtils
::pickRandom( $currentLoads );
459 $laggedReplicaMode = true;
463 if ( $i === false ) {
464 // pickRandom() returned false.
465 // This is permanent and means the configuration or the load monitor
466 // wants us to return false.
467 $this->connLogger
->debug( __METHOD__
. ": pickRandom() returned false" );
469 return [ false, false ];
472 $serverName = $this->getServerName( $i );
473 $this->connLogger
->debug( __METHOD__
. ": Using reader #$i: $serverName..." );
475 $conn = $this->openConnection( $i, $domain );
477 $this->connLogger
->warning( __METHOD__
. ": Failed connecting to $i/$domain" );
478 unset( $currentLoads[$i] ); // avoid this server next iteration
483 // Decrement reference counter, we are finished with this connection.
484 // It will be incremented for the caller later.
485 if ( $domain !== false ) {
486 $this->reuseConnection( $conn );
489 // Return this server
493 // If all servers were down, quit now
494 if ( !count( $currentLoads ) ) {
495 $this->connLogger
->error( __METHOD__
. ": all servers down" );
498 return [ $i, $laggedReplicaMode ];
501 public function waitFor( $pos ) {
502 $oldPos = $this->waitForPos
;
504 $this->waitForPos
= $pos;
505 // If a generic reader connection was already established, then wait now
506 $i = $this->readIndex
;
508 if ( !$this->doWait( $i ) ) {
509 $this->laggedReplicaMode
= true;
513 // Restore the older position if it was higher since this is used for lag-protection
514 $this->setWaitForPositionIfHigher( $oldPos );
518 public function waitForOne( $pos, $timeout = null ) {
519 $oldPos = $this->waitForPos
;
521 $this->waitForPos
= $pos;
523 $i = $this->readIndex
;
525 // Pick a generic replica DB if there isn't one yet
526 $readLoads = $this->loads
;
527 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
528 $readLoads = array_filter( $readLoads ); // with non-zero load
529 $i = ArrayUtils
::pickRandom( $readLoads );
533 $ok = $this->doWait( $i, true, $timeout );
535 $ok = true; // no applicable loads
538 # Restore the old position, as this is not used for lag-protection but for throttling
539 $this->waitForPos
= $oldPos;
545 public function waitForAll( $pos, $timeout = null ) {
546 $timeout = $timeout ?
: $this->waitTimeout
;
548 $oldPos = $this->waitForPos
;
550 $this->waitForPos
= $pos;
551 $serverCount = count( $this->servers
);
554 for ( $i = 1; $i < $serverCount; $i++
) {
555 if ( $this->loads
[$i] > 0 ) {
556 $start = microtime( true );
557 $ok = $this->doWait( $i, true, $timeout ) && $ok;
558 $timeout -= intval( microtime( true ) - $start );
559 if ( $timeout <= 0 ) {
560 break; // timeout reached
565 # Restore the old position, as this is not used for lag-protection but for throttling
566 $this->waitForPos
= $oldPos;
573 * @param DBMasterPos|bool $pos
575 private function setWaitForPositionIfHigher( $pos ) {
580 if ( !$this->waitForPos ||
$pos->hasReached( $this->waitForPos
) ) {
581 $this->waitForPos
= $pos;
585 public function getAnyOpenConnection( $i, $flags = 0 ) {
586 $autocommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
587 foreach ( $this->conns
as $connsByServer ) {
588 if ( !isset( $connsByServer[$i] ) ) {
592 foreach ( $connsByServer[$i] as $conn ) {
593 if ( !$autocommit ||
$conn->getLBInfo( 'autoCommitOnly' ) ) {
603 * Wait for a given replica DB to catch up to the master pos stored in $this
604 * @param int $index Server index
605 * @param bool $open Check the server even if a new connection has to be made
606 * @param int|null $timeout Max seconds to wait; default is "waitTimeout" given to __construct()
609 protected function doWait( $index, $open = false, $timeout = null ) {
610 $timeout = max( 1, intval( $timeout ?
: $this->waitTimeout
) );
612 // Check if we already know that the DB has reached this point
613 $server = $this->getServerName( $index );
614 $key = $this->srvCache
->makeGlobalKey( __CLASS__
, 'last-known-pos', $server, 'v1' );
615 /** @var DBMasterPos $knownReachedPos */
616 $knownReachedPos = $this->srvCache
->get( $key );
618 $knownReachedPos instanceof DBMasterPos
&&
619 $knownReachedPos->hasReached( $this->waitForPos
)
621 $this->replLogger
->debug(
623 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
624 [ 'dbserver' => $server ]
629 // Find a connection to wait on, creating one if needed and allowed
630 $close = false; // close the connection afterwards
631 $conn = $this->getAnyOpenConnection( $index );
634 $this->replLogger
->debug(
635 __METHOD__
. ': no connection open for {dbserver}',
636 [ 'dbserver' => $server ]
641 $conn = $this->openConnection( $index, self
::DOMAIN_ANY
);
643 $this->replLogger
->warning(
644 __METHOD__
. ': failed to connect to {dbserver}',
645 [ 'dbserver' => $server ]
650 // Avoid connection spam in waitForAll() when connections
651 // are made just for the sake of doing this lag check.
656 $this->replLogger
->info(
658 ': waiting for replica DB {dbserver} to catch up...',
659 [ 'dbserver' => $server ]
662 $result = $conn->masterPosWait( $this->waitForPos
, $timeout );
664 if ( $result === null ) {
665 $this->replLogger
->warning(
666 __METHOD__
. ': Errored out waiting on {host} pos {pos}',
669 'pos' => $this->waitForPos
,
670 'trace' => ( new RuntimeException() )->getTraceAsString()
674 } elseif ( $result == -1 ) {
675 $this->replLogger
->warning(
676 __METHOD__
. ': Timed out waiting on {host} pos {pos}',
679 'pos' => $this->waitForPos
,
680 'trace' => ( new RuntimeException() )->getTraceAsString()
685 $this->replLogger
->debug( __METHOD__
. ": done waiting" );
687 // Remember that the DB reached this point
688 $this->srvCache
->set( $key, $this->waitForPos
, BagOStuff
::TTL_DAY
);
692 $this->closeConnection( $conn );
698 public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
699 if ( $i === null ||
$i === false ) {
700 throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__
.
701 ' with invalid server index' );
704 if ( $this->localDomain
->equals( $domain ) ||
$domain === $this->localDomainIdAlias
) {
705 $domain = false; // local connection requested
708 if ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) === self
::CONN_TRX_AUTOCOMMIT
) {
709 // Assuming all servers are of the same type (or similar), which is overwhelmingly
710 // the case, use the master server information to get the attributes. The information
711 // for $i cannot be used since it might be DB_REPLICA, which might require connection
712 // attempts in order to be resolved into a real server index.
713 $attributes = $this->getServerAttributes( $this->getWriterIndex() );
714 if ( $attributes[Database
::ATTR_DB_LEVEL_LOCKING
] ) {
715 // Callers sometimes want to (a) escape REPEATABLE-READ stateness without locking
716 // rows (e.g. FOR UPDATE) or (b) make small commits during a larger transactions
717 // to reduce lock contention. None of these apply for sqlite and using separate
718 // connections just causes self-deadlocks.
719 $flags &= ~self
::CONN_TRX_AUTOCOMMIT
;
720 $this->connLogger
->info( __METHOD__
.
721 ': ignoring CONN_TRX_AUTOCOMMIT to avoid deadlocks.' );
725 // Check one "group" per default: the generic pool
726 $defaultGroups = $this->defaultGroup ?
[ $this->defaultGroup
] : [ false ];
728 $groups = ( $groups === false ||
$groups === [] )
732 $masterOnly = ( $i == self
::DB_MASTER ||
$i == $this->getWriterIndex() );
733 $oldConnsOpened = $this->connsOpened
; // connections open now
735 if ( $i == self
::DB_MASTER
) {
736 $i = $this->getWriterIndex();
737 } elseif ( $i == self
::DB_REPLICA
) {
738 # Try to find an available server in any the query groups (in order)
739 foreach ( $groups as $group ) {
740 $groupIndex = $this->getReaderIndex( $group, $domain );
741 if ( $groupIndex !== false ) {
748 # Operation-based index
749 if ( $i == self
::DB_REPLICA
) {
750 $this->lastError
= 'Unknown error'; // reset error string
751 # Try the general server pool if $groups are unavailable.
752 $i = ( $groups === [ false ] )
753 ?
false // don't bother with this if that is what was tried above
754 : $this->getReaderIndex( false, $domain );
755 # Couldn't find a working server in getReaderIndex()?
756 if ( $i === false ) {
757 $this->lastError
= 'No working replica DB server: ' . $this->lastError
;
758 // Throw an exception
759 $this->reportConnectionError();
760 return null; // not reached
764 # Now we have an explicit index into the servers array
765 $conn = $this->openConnection( $i, $domain, $flags );
767 // Throw an exception
768 $this->reportConnectionError();
769 return null; // not reached
772 # Profile any new connections that happen
773 if ( $this->connsOpened
> $oldConnsOpened ) {
774 $host = $conn->getServer();
775 $dbname = $conn->getDBname();
776 $this->trxProfiler
->recordConnection( $host, $dbname, $masterOnly );
780 # Make master-requested DB handles inherit any read-only mode setting
781 $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
787 public function reuseConnection( IDatabase
$conn ) {
788 $serverIndex = $conn->getLBInfo( 'serverIndex' );
789 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
790 if ( $serverIndex === null ||
$refCount === null ) {
792 * This can happen in code like:
793 * foreach ( $dbs as $db ) {
794 * $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
796 * $lb->reuseConnection( $conn );
798 * When a connection to the local DB is opened in this way, reuseConnection()
802 } elseif ( $conn instanceof DBConnRef
) {
803 // DBConnRef already handles calling reuseConnection() and only passes the live
804 // Database instance to this method. Any caller passing in a DBConnRef is broken.
805 $this->connLogger
->error(
806 __METHOD__
. ": got DBConnRef instance.\n" .
807 ( new RuntimeException() )->getTraceAsString() );
812 if ( $this->disabled
) {
813 return; // DBConnRef handle probably survived longer than the LoadBalancer
816 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
817 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
818 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
820 $connFreeKey = self
::KEY_FOREIGN_FREE
;
821 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
824 $domain = $conn->getDomainID();
825 if ( !isset( $this->conns
[$connInUseKey][$serverIndex][$domain] ) ) {
826 throw new InvalidArgumentException( __METHOD__
.
827 ": connection $serverIndex/$domain not found; it may have already been freed." );
828 } elseif ( $this->conns
[$connInUseKey][$serverIndex][$domain] !== $conn ) {
829 throw new InvalidArgumentException( __METHOD__
.
830 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
833 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
834 if ( $refCount <= 0 ) {
835 $this->conns
[$connFreeKey][$serverIndex][$domain] = $conn;
836 unset( $this->conns
[$connInUseKey][$serverIndex][$domain] );
837 if ( !$this->conns
[$connInUseKey][$serverIndex] ) {
838 unset( $this->conns
[$connInUseKey][$serverIndex] ); // clean up
840 $this->connLogger
->debug( __METHOD__
. ": freed connection $serverIndex/$domain" );
842 $this->connLogger
->debug( __METHOD__
.
843 ": reference count for $serverIndex/$domain reduced to $refCount" );
847 public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
848 $domain = $this->resolveDomainID( $domain );
850 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
853 public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
854 $domain = $this->resolveDomainID( $domain );
856 return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
859 public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
860 $domain = $this->resolveDomainID( $domain );
862 return new MaintainableDBConnRef(
863 $this, $this->getConnection( $db, $groups, $domain, $flags ) );
866 public function openConnection( $i, $domain = false, $flags = 0 ) {
867 if ( $this->localDomain
->equals( $domain ) ||
$domain === $this->localDomainIdAlias
) {
868 $domain = false; // local connection requested
871 if ( !$this->connectionAttempted
&& $this->chronologyCallback
) {
872 $this->connLogger
->debug( __METHOD__
. ': calling initLB() before first connection.' );
873 // Load any "waitFor" positions before connecting so that doWait() is triggered
874 $this->connectionAttempted
= true;
875 ( $this->chronologyCallback
)( $this );
878 // Check if an auto-commit connection is being requested. If so, it will not reuse the
879 // main set of DB connections but rather its own pool since:
880 // a) those are usually set to implicitly use transaction rounds via DBO_TRX
881 // b) those must support the use of explicit transaction rounds via beginMasterChanges()
882 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
884 if ( $domain !== false ) {
885 // Connection is to a foreign domain
886 $conn = $this->openForeignConnection( $i, $domain, $flags );
888 // Connection is to the local domain
889 $conn = $this->openLocalConnection( $i, $flags );
892 if ( $conn instanceof IDatabase
&& !$conn->isOpen() ) {
893 // Connection was made but later unrecoverably lost for some reason.
894 // Do not return a handle that will just throw exceptions on use,
895 // but let the calling code (e.g. getReaderIndex) try another server.
896 // See DatabaseMyslBase::ping() for how this can happen.
897 $this->errorConnection
= $conn;
901 if ( $autoCommit && $conn instanceof IDatabase
) {
902 if ( $conn->trxLevel() ) { // sanity
903 throw new DBUnexpectedError(
905 __METHOD__
. ': CONN_TRX_AUTOCOMMIT handle has a transaction.'
909 $conn->clearFlag( $conn::DBO_TRX
); // auto-commit mode
916 * Open a connection to a local DB, or return one if it is already open.
918 * On error, returns false, and the connection which caused the
919 * error will be available via $this->errorConnection.
921 * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
923 * @param int $i Server index
924 * @param int $flags Class CONN_* constant bitfield
927 private function openLocalConnection( $i, $flags = 0 ) {
928 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
930 $connKey = $autoCommit ? self
::KEY_LOCAL_NOROUND
: self
::KEY_LOCAL
;
931 if ( isset( $this->conns
[$connKey][$i][0] ) ) {
932 $conn = $this->conns
[$connKey][$i][0];
934 if ( !isset( $this->servers
[$i] ) ||
!is_array( $this->servers
[$i] ) ) {
935 throw new InvalidArgumentException( "No server with index '$i'." );
937 // Open a new connection
938 $server = $this->servers
[$i];
939 $server['serverIndex'] = $i;
940 $server['autoCommitOnly'] = $autoCommit;
941 $conn = $this->reallyOpenConnection( $server, $this->localDomain
);
942 $host = $this->getServerName( $i );
943 if ( $conn->isOpen() ) {
944 $this->connLogger
->debug(
945 __METHOD__
. ": connected to database $i at '$host'." );
946 $this->conns
[$connKey][$i][0] = $conn;
948 $this->connLogger
->warning(
949 __METHOD__
. ": failed to connect to database $i at '$host'." );
950 $this->errorConnection
= $conn;
959 * Open a connection to a foreign DB, or return one if it is already open.
961 * Increments a reference count on the returned connection which locks the
962 * connection to the requested domain. This reference count can be
963 * decremented by calling reuseConnection().
965 * If a connection is open to the appropriate server already, but with the wrong
966 * database, it will be switched to the right database and returned, as long as
967 * it has been freed first with reuseConnection().
969 * On error, returns false, and the connection which caused the
970 * error will be available via $this->errorConnection.
972 * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
974 * @param int $i Server index
975 * @param string $domain Domain ID to open
976 * @param int $flags Class CONN_* constant bitfield
979 private function openForeignConnection( $i, $domain, $flags = 0 ) {
980 $domainInstance = DatabaseDomain
::newFromId( $domain );
981 $dbName = $domainInstance->getDatabase();
982 $prefix = $domainInstance->getTablePrefix();
983 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTOCOMMIT
) == self
::CONN_TRX_AUTOCOMMIT
);
986 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
987 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
989 $connFreeKey = self
::KEY_FOREIGN_FREE
;
990 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
993 if ( isset( $this->conns
[$connInUseKey][$i][$domain] ) ) {
994 // Reuse an in-use connection for the same domain
995 $conn = $this->conns
[$connInUseKey][$i][$domain];
996 $this->connLogger
->debug( __METHOD__
. ": reusing connection $i/$domain" );
997 } elseif ( isset( $this->conns
[$connFreeKey][$i][$domain] ) ) {
998 // Reuse a free connection for the same domain
999 $conn = $this->conns
[$connFreeKey][$i][$domain];
1000 unset( $this->conns
[$connFreeKey][$i][$domain] );
1001 $this->conns
[$connInUseKey][$i][$domain] = $conn;
1002 $this->connLogger
->debug( __METHOD__
. ": reusing free connection $i/$domain" );
1003 } elseif ( !empty( $this->conns
[$connFreeKey][$i] ) ) {
1004 // Reuse a free connection from another domain
1005 $conn = reset( $this->conns
[$connFreeKey][$i] );
1006 $oldDomain = key( $this->conns
[$connFreeKey][$i] );
1007 if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
1008 $this->lastError
= "Error selecting database '$dbName' on server " .
1009 $conn->getServer() . " from client host {$this->hostname}";
1010 $this->errorConnection
= $conn;
1013 $conn->tablePrefix( $prefix );
1014 unset( $this->conns
[$connFreeKey][$i][$oldDomain] );
1015 // Note that if $domain is an empty string, getDomainID() might not match it
1016 $this->conns
[$connInUseKey][$i][$conn->getDomainId()] = $conn;
1017 $this->connLogger
->debug( __METHOD__
.
1018 ": reusing free connection from $oldDomain for $domain" );
1021 if ( !isset( $this->servers
[$i] ) ||
!is_array( $this->servers
[$i] ) ) {
1022 throw new InvalidArgumentException( "No server with index '$i'." );
1024 // Open a new connection
1025 $server = $this->servers
[$i];
1026 $server['serverIndex'] = $i;
1027 $server['foreignPoolRefCount'] = 0;
1028 $server['foreign'] = true;
1029 $server['autoCommitOnly'] = $autoCommit;
1030 $conn = $this->reallyOpenConnection( $server, $domainInstance );
1031 if ( !$conn->isOpen() ) {
1032 $this->connLogger
->warning( __METHOD__
. ": connection error for $i/$domain" );
1033 $this->errorConnection
= $conn;
1036 // Note that if $domain is an empty string, getDomainID() might not match it
1037 $this->conns
[$connInUseKey][$i][$conn->getDomainID()] = $conn;
1038 $this->connLogger
->debug( __METHOD__
. ": opened new connection for $i/$domain" );
1042 // Increment reference count
1043 if ( $conn instanceof IDatabase
) {
1044 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
1045 $conn->setLBInfo( 'foreignPoolRefCount', $refCount +
1 );
1051 public function getServerAttributes( $i ) {
1052 return Database
::attributesFromType(
1053 $this->getServerType( $i ),
1054 $this->servers
[$i]['driver'] ??
null
1059 * Test if the specified index represents an open connection
1061 * @param int $index Server index
1065 private function isOpen( $index ) {
1066 if ( !is_int( $index ) ) {
1070 return (bool)$this->getAnyOpenConnection( $index );
1074 * Open a new network connection to a server (uncached)
1076 * Returns a Database object whether or not the connection was successful.
1078 * @param array $server
1079 * @param DatabaseDomain $domain Domain the connection is for, possibly unspecified
1081 * @throws DBAccessError
1082 * @throws InvalidArgumentException
1084 protected function reallyOpenConnection( array $server, DatabaseDomain
$domain ) {
1085 if ( $this->disabled
) {
1086 throw new DBAccessError();
1089 if ( $domain->getDatabase() === null ) {
1090 // The database domain does not specify a DB name and some database systems require a
1091 // valid DB specified on connection. The $server configuration array contains a default
1092 // DB name to use for connections in such cases.
1093 if ( $server['type'] === 'mysql' ) {
1094 // For MySQL, DATABASE and SCHEMA are synonyms, connections need not specify a DB,
1095 // and the DB name in $server might not exist due to legacy reasons (the default
1096 // domain used to ignore the local LB domain, even when mismatched).
1097 $server['dbname'] = null;
1100 $server['dbname'] = $domain->getDatabase();
1103 if ( $domain->getSchema() !== null ) {
1104 $server['schema'] = $domain->getSchema();
1107 // It is always possible to connect with any prefix, even the empty string
1108 $server['tablePrefix'] = $domain->getTablePrefix();
1110 // Let the handle know what the cluster master is (e.g. "db1052")
1111 $masterName = $this->getServerName( $this->getWriterIndex() );
1112 $server['clusterMasterHost'] = $masterName;
1114 // Log when many connection are made on requests
1115 if ( ++
$this->connsOpened
>= self
::CONN_HELD_WARN_THRESHOLD
) {
1116 $this->perfLogger
->warning( __METHOD__
. ": " .
1117 "{$this->connsOpened}+ connections made (master=$masterName)" );
1120 $server['srvCache'] = $this->srvCache
;
1121 // Set loggers and profilers
1122 $server['connLogger'] = $this->connLogger
;
1123 $server['queryLogger'] = $this->queryLogger
;
1124 $server['errorLogger'] = $this->errorLogger
;
1125 $server['deprecationLogger'] = $this->deprecationLogger
;
1126 $server['profiler'] = $this->profiler
;
1127 $server['trxProfiler'] = $this->trxProfiler
;
1128 // Use the same agent and PHP mode for all DB handles
1129 $server['cliMode'] = $this->cliMode
;
1130 $server['agent'] = $this->agent
;
1131 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
1132 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
1133 $server['flags'] = $server['flags'] ?? IDatabase
::DBO_DEFAULT
;
1135 // Create a live connection object
1137 $db = Database
::factory( $server['type'], $server );
1138 } catch ( DBConnectionError
$e ) {
1139 // FIXME: This is probably the ugliest thing I have ever done to
1140 // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
1144 $db->setLBInfo( $server );
1145 $db->setLazyMasterHandle(
1146 $this->getLazyConnectionRef( self
::DB_MASTER
, [], $db->getDomainID() )
1148 $db->setTableAliases( $this->tableAliases
);
1149 $db->setIndexAliases( $this->indexAliases
);
1151 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1152 if ( $this->trxRoundId
!== false ) {
1153 $this->applyTransactionRoundFlags( $db );
1155 foreach ( $this->trxRecurringCallbacks
as $name => $callback ) {
1156 $db->setTransactionListener( $name, $callback );
1164 * @throws DBConnectionError
1166 private function reportConnectionError() {
1167 $conn = $this->errorConnection
; // the connection which caused the error
1169 'method' => __METHOD__
,
1170 'last_error' => $this->lastError
,
1173 if ( $conn instanceof IDatabase
) {
1174 $context['db_server'] = $conn->getServer();
1175 $this->connLogger
->warning(
1176 __METHOD__
. ": connection error: {last_error} ({db_server})",
1180 throw new DBConnectionError( $conn, "{$this->lastError} ({$context['db_server']})" );
1182 // No last connection, probably due to all servers being too busy
1183 $this->connLogger
->error(
1185 ": LB failure with no last connection. Connection error: {last_error}",
1189 // If all servers were busy, "lastError" will contain something sensible
1190 throw new DBConnectionError( null, $this->lastError
);
1194 public function getWriterIndex() {
1198 public function haveIndex( $i ) {
1199 return array_key_exists( $i, $this->servers
);
1202 public function isNonZeroLoad( $i ) {
1203 return array_key_exists( $i, $this->servers
) && $this->loads
[$i] != 0;
1206 public function getServerCount() {
1207 return count( $this->servers
);
1210 public function getServerName( $i ) {
1211 if ( isset( $this->servers
[$i]['hostName'] ) ) {
1212 $name = $this->servers
[$i]['hostName'];
1213 } elseif ( isset( $this->servers
[$i]['host'] ) ) {
1214 $name = $this->servers
[$i]['host'];
1219 return ( $name != '' ) ?
$name : 'localhost';
1222 public function getServerInfo( $i ) {
1223 if ( isset( $this->servers
[$i] ) ) {
1224 return $this->servers
[$i];
1230 public function getServerType( $i ) {
1231 return $this->servers
[$i]['type'] ??
'unknown';
1234 public function getMasterPos() {
1235 # If this entire request was served from a replica DB without opening a connection to the
1236 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1237 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1238 if ( !$masterConn ) {
1239 $serverCount = count( $this->servers
);
1240 for ( $i = 1; $i < $serverCount; $i++
) {
1241 $conn = $this->getAnyOpenConnection( $i );
1243 return $conn->getReplicaPos();
1247 return $masterConn->getMasterPos();
1253 public function disable() {
1255 $this->disabled
= true;
1258 public function closeAll() {
1259 $this->forEachOpenConnection( function ( IDatabase
$conn ) {
1260 $host = $conn->getServer();
1261 $this->connLogger
->debug(
1262 __METHOD__
. ": closing connection to database '$host'." );
1267 self
::KEY_LOCAL
=> [],
1268 self
::KEY_FOREIGN_INUSE
=> [],
1269 self
::KEY_FOREIGN_FREE
=> [],
1270 self
::KEY_LOCAL_NOROUND
=> [],
1271 self
::KEY_FOREIGN_INUSE_NOROUND
=> [],
1272 self
::KEY_FOREIGN_FREE_NOROUND
=> []
1274 $this->connsOpened
= 0;
1277 public function closeConnection( IDatabase
$conn ) {
1278 $serverIndex = $conn->getLBInfo( 'serverIndex' );
1279 foreach ( $this->conns
as $type => $connsByServer ) {
1280 if ( !isset( $connsByServer[$serverIndex] ) ) {
1284 foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1285 if ( $conn === $trackedConn ) {
1286 $host = $this->getServerName( $i );
1287 $this->connLogger
->debug(
1288 __METHOD__
. ": closing connection to database $i at '$host'." );
1289 unset( $this->conns
[$type][$serverIndex][$i] );
1290 --$this->connsOpened
;
1299 public function commitAll( $fname = __METHOD__
) {
1300 $this->commitMasterChanges( $fname );
1301 $this->flushMasterSnapshots( $fname );
1302 $this->flushReplicaSnapshots( $fname );
1305 public function finalizeMasterChanges() {
1306 $this->assertTransactionRoundStage( [ self
::ROUND_CURSORY
, self
::ROUND_FINALIZED
] );
1308 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1309 // Loop until callbacks stop adding callbacks on other connections
1312 $count = 0; // callbacks execution attempts
1313 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( &$count ) {
1314 // Run any pre-commit callbacks while leaving the post-commit ones suppressed.
1315 // Any error should cause all (peer) transactions to be rolled back together.
1316 $count +
= $conn->runOnTransactionPreCommitCallbacks();
1319 } while ( $count > 0 );
1320 // Defer post-commit callbacks until after COMMIT/ROLLBACK happens on all handles
1321 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1322 $conn->setTrxEndCallbackSuppression( true );
1324 $this->trxRoundStage
= self
::ROUND_FINALIZED
;
1329 public function approveMasterChanges( array $options ) {
1330 $this->assertTransactionRoundStage( self
::ROUND_FINALIZED
);
1332 $limit = $options['maxWriteDuration'] ??
0;
1334 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1335 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $limit ) {
1336 // If atomic sections or explicit transactions are still open, some caller must have
1337 // caught an exception but failed to properly rollback any changes. Detect that and
1338 // throw and error (causing rollback).
1339 if ( $conn->explicitTrxActive() ) {
1340 throw new DBTransactionError(
1342 "Explicit transaction still active. A caller may have caught an error."
1345 // Assert that the time to replicate the transaction will be sane.
1346 // If this fails, then all DB transactions will be rollback back together.
1347 $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY
);
1348 if ( $limit > 0 && $time > $limit ) {
1349 throw new DBTransactionSizeError(
1351 "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
1355 // If a connection sits idle while slow queries execute on another, that connection
1356 // may end up dropped before the commit round is reached. Ping servers to detect this.
1357 if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1358 throw new DBTransactionError(
1360 "A connection to the {$conn->getDBname()} database was lost before commit."
1364 $this->trxRoundStage
= self
::ROUND_APPROVED
;
1367 public function beginMasterChanges( $fname = __METHOD__
) {
1368 if ( $this->trxRoundId
!== false ) {
1369 throw new DBTransactionError(
1371 "$fname: Transaction round '{$this->trxRoundId}' already started."
1374 $this->assertTransactionRoundStage( self
::ROUND_CURSORY
);
1376 // Clear any empty transactions (no writes/callbacks) from the implicit round
1377 $this->flushMasterSnapshots( $fname );
1379 $this->trxRoundId
= $fname;
1380 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1381 // Mark applicable handles as participating in this explicit transaction round.
1382 // For each of these handles, any writes and callbacks will be tied to a single
1383 // transaction. The (peer) handles will reject begin()/commit() calls unless they
1384 // are part of an en masse commit or an en masse rollback.
1385 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1386 $this->applyTransactionRoundFlags( $conn );
1388 $this->trxRoundStage
= self
::ROUND_CURSORY
;
1391 public function commitMasterChanges( $fname = __METHOD__
) {
1392 $this->assertTransactionRoundStage( self
::ROUND_APPROVED
);
1396 /** @noinspection PhpUnusedLocalVariableInspection */
1397 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1399 $restore = ( $this->trxRoundId
!== false );
1400 $this->trxRoundId
= false;
1401 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1402 // Commit any writes and clear any snapshots as well (callbacks require AUTOCOMMIT).
1403 // Note that callbacks should already be suppressed due to finalizeMasterChanges().
1404 $this->forEachOpenMasterConnection(
1405 function ( IDatabase
$conn ) use ( $fname, &$failures ) {
1407 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1408 } catch ( DBError
$e ) {
1409 ( $this->errorLogger
)( $e );
1410 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1415 throw new DBTransactionError(
1417 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1421 // Unmark handles as participating in this explicit transaction round
1422 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1423 $this->undoTransactionRoundFlags( $conn );
1426 $this->trxRoundStage
= self
::ROUND_COMMIT_CALLBACKS
;
1429 public function runMasterTransactionIdleCallbacks() {
1430 if ( $this->trxRoundStage
=== self
::ROUND_COMMIT_CALLBACKS
) {
1431 $type = IDatabase
::TRIGGER_COMMIT
;
1432 } elseif ( $this->trxRoundStage
=== self
::ROUND_ROLLBACK_CALLBACKS
) {
1433 $type = IDatabase
::TRIGGER_ROLLBACK
;
1435 throw new DBTransactionError(
1437 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1441 $oldStage = $this->trxRoundStage
;
1442 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1444 // Now that the COMMIT/ROLLBACK step is over, enable post-commit callback runs
1445 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1446 $conn->setTrxEndCallbackSuppression( false );
1449 $e = null; // first exception
1450 // Loop until callbacks stop adding callbacks on other connections
1452 // Run any pending callbacks for each connection...
1453 $count = 0; // callback execution attempts
1454 $this->forEachOpenMasterConnection(
1455 function ( Database
$conn ) use ( $type, &$e, &$count ) {
1456 if ( $conn->trxLevel() ) {
1457 return; // retry in the next iteration, after commit() is called
1460 $count +
= $conn->runOnTransactionIdleCallbacks( $type );
1461 } catch ( Exception
$ex ) {
1466 // Clear out any active transactions left over from callbacks...
1467 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( &$e ) {
1468 if ( $conn->writesPending() ) {
1469 // A callback from another handle wrote to this one and DBO_TRX is set
1470 $this->queryLogger
->warning( __METHOD__
. ": found writes pending." );
1471 $fnames = implode( ', ', $conn->pendingWriteAndCallbackCallers() );
1472 $this->queryLogger
->warning(
1473 __METHOD__
. ": found writes pending ($fnames).",
1475 'db_server' => $conn->getServer(),
1476 'db_name' => $conn->getDBname()
1479 } elseif ( $conn->trxLevel() ) {
1480 // A callback from another handle read from this one and DBO_TRX is set,
1481 // which can easily happen if there is only one DB (no replicas)
1482 $this->queryLogger
->debug( __METHOD__
. ": found empty transaction." );
1485 $conn->commit( __METHOD__
, $conn::FLUSHING_ALL_PEERS
);
1486 } catch ( Exception
$ex ) {
1490 } while ( $count > 0 );
1492 $this->trxRoundStage
= $oldStage;
1497 public function runMasterTransactionListenerCallbacks() {
1498 if ( $this->trxRoundStage
=== self
::ROUND_COMMIT_CALLBACKS
) {
1499 $type = IDatabase
::TRIGGER_COMMIT
;
1500 } elseif ( $this->trxRoundStage
=== self
::ROUND_ROLLBACK_CALLBACKS
) {
1501 $type = IDatabase
::TRIGGER_ROLLBACK
;
1503 throw new DBTransactionError(
1505 "Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
1511 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1512 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( $type, &$e ) {
1514 $conn->runTransactionListenerCallbacks( $type );
1515 } catch ( Exception
$ex ) {
1519 $this->trxRoundStage
= self
::ROUND_CURSORY
;
1524 public function rollbackMasterChanges( $fname = __METHOD__
) {
1525 $restore = ( $this->trxRoundId
!== false );
1526 $this->trxRoundId
= false;
1527 $this->trxRoundStage
= self
::ROUND_ERROR
; // "failed" until proven otherwise
1528 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $fname ) {
1529 $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS
);
1532 // Unmark handles as participating in this explicit transaction round
1533 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1534 $this->undoTransactionRoundFlags( $conn );
1537 $this->trxRoundStage
= self
::ROUND_ROLLBACK_CALLBACKS
;
1541 * @param string|string[] $stage
1543 private function assertTransactionRoundStage( $stage ) {
1544 $stages = (array)$stage;
1546 if ( !in_array( $this->trxRoundStage
, $stages, true ) ) {
1547 $stageList = implode(
1549 array_map( function ( $v ) {
1553 throw new DBTransactionError(
1555 "Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
1561 * Make all DB servers with DBO_DEFAULT/DBO_TRX set join the transaction round
1563 * Some servers may have neither flag enabled, meaning that they opt out of such
1564 * transaction rounds and remain in auto-commit mode. Such behavior might be desired
1565 * when a DB server is used for something like simple key/value storage.
1567 * @param Database $conn
1569 private function applyTransactionRoundFlags( Database
$conn ) {
1570 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1571 return; // transaction rounds do not apply to these connections
1574 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1575 // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1576 // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1577 $conn->setFlag( $conn::DBO_TRX
, $conn::REMEMBER_PRIOR
);
1580 if ( $conn->getFlag( $conn::DBO_TRX
) ) {
1581 $conn->setLBInfo( 'trxRoundId', $this->trxRoundId
);
1586 * @param Database $conn
1588 private function undoTransactionRoundFlags( Database
$conn ) {
1589 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1590 return; // transaction rounds do not apply to these connections
1593 if ( $conn->getFlag( $conn::DBO_TRX
) ) {
1594 $conn->setLBInfo( 'trxRoundId', false );
1597 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1598 $conn->restoreFlags( $conn::RESTORE_PRIOR
);
1602 public function flushReplicaSnapshots( $fname = __METHOD__
) {
1603 $this->forEachOpenReplicaConnection( function ( IDatabase
$conn ) use ( $fname ) {
1604 $conn->flushSnapshot( $fname );
1608 public function flushMasterSnapshots( $fname = __METHOD__
) {
1609 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $fname ) {
1610 $conn->flushSnapshot( $fname );
1618 public function getTransactionRoundStage() {
1619 return $this->trxRoundStage
;
1622 public function hasMasterConnection() {
1623 return $this->isOpen( $this->getWriterIndex() );
1626 public function hasMasterChanges() {
1628 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$pending ) {
1629 $pending |
= $conn->writesOrCallbacksPending();
1632 return (bool)$pending;
1635 public function lastMasterChangeTimestamp() {
1637 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$lastTime ) {
1638 $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1644 public function hasOrMadeRecentMasterChanges( $age = null ) {
1645 $age = ( $age === null ) ?
$this->waitTimeout
: $age;
1647 return ( $this->hasMasterChanges()
1648 ||
$this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1651 public function pendingMasterChangeCallers() {
1653 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$fnames ) {
1654 $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1660 public function getLaggedReplicaMode( $domain = false ) {
1661 // No-op if there is only one DB (also avoids recursion)
1662 if ( !$this->laggedReplicaMode
&& $this->getServerCount() > 1 ) {
1664 // See if laggedReplicaMode gets set
1665 $conn = $this->getConnection( self
::DB_REPLICA
, false, $domain );
1666 $this->reuseConnection( $conn );
1667 } catch ( DBConnectionError
$e ) {
1668 // Avoid expensive re-connect attempts and failures
1669 $this->allReplicasDownMode
= true;
1670 $this->laggedReplicaMode
= true;
1674 return $this->laggedReplicaMode
;
1677 public function laggedReplicaUsed() {
1678 return $this->laggedReplicaMode
;
1684 * @deprecated Since 1.28; use laggedReplicaUsed()
1686 public function laggedSlaveUsed() {
1687 return $this->laggedReplicaUsed();
1690 public function getReadOnlyReason( $domain = false, IDatabase
$conn = null ) {
1691 if ( $this->readOnlyReason
!== false ) {
1692 return $this->readOnlyReason
;
1693 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1694 if ( $this->allReplicasDownMode
) {
1695 return 'The database has been automatically locked ' .
1696 'until the replica database servers become available';
1698 return 'The database has been automatically locked ' .
1699 'while the replica database servers catch up to the master.';
1701 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1702 return 'The database master is running in read-only mode.';
1709 * @param string $domain Domain ID, or false for the current domain
1710 * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1713 private function masterRunningReadOnly( $domain, IDatabase
$conn = null ) {
1714 $cache = $this->wanCache
;
1715 $masterServer = $this->getServerName( $this->getWriterIndex() );
1717 return (bool)$cache->getWithSetCallback(
1718 $cache->makeGlobalKey( __CLASS__
, 'server-read-only', $masterServer ),
1719 self
::TTL_CACHE_READONLY
,
1720 function () use ( $domain, $conn ) {
1721 $old = $this->trxProfiler
->setSilenced( true );
1723 $dbw = $conn ?
: $this->getConnection( self
::DB_MASTER
, [], $domain );
1724 $readOnly = (int)$dbw->serverIsReadOnly();
1726 $this->reuseConnection( $dbw );
1728 } catch ( DBError
$e ) {
1731 $this->trxProfiler
->setSilenced( $old );
1734 [ 'pcTTL' => $cache::TTL_PROC_LONG
, 'busyValue' => 0 ]
1738 public function allowLagged( $mode = null ) {
1739 if ( $mode === null ) {
1740 return $this->allowLagged
;
1742 $this->allowLagged
= $mode;
1744 return $this->allowLagged
;
1747 public function pingAll() {
1749 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$success ) {
1750 if ( !$conn->ping() ) {
1758 public function forEachOpenConnection( $callback, array $params = [] ) {
1759 foreach ( $this->conns
as $connsByServer ) {
1760 foreach ( $connsByServer as $serverConns ) {
1761 foreach ( $serverConns as $conn ) {
1762 $callback( $conn, ...$params );
1768 public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1769 $masterIndex = $this->getWriterIndex();
1770 foreach ( $this->conns
as $connsByServer ) {
1771 if ( isset( $connsByServer[$masterIndex] ) ) {
1772 /** @var IDatabase $conn */
1773 foreach ( $connsByServer[$masterIndex] as $conn ) {
1774 $callback( $conn, ...$params );
1780 public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1781 foreach ( $this->conns
as $connsByServer ) {
1782 foreach ( $connsByServer as $i => $serverConns ) {
1783 if ( $i === $this->getWriterIndex() ) {
1784 continue; // skip master
1786 foreach ( $serverConns as $conn ) {
1787 $callback( $conn, ...$params );
1793 public function getMaxLag( $domain = false ) {
1798 if ( $this->getServerCount() <= 1 ) {
1799 return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1802 $lagTimes = $this->getLagTimes( $domain );
1803 foreach ( $lagTimes as $i => $lag ) {
1804 if ( $this->loads
[$i] > 0 && $lag > $maxLag ) {
1806 $host = $this->servers
[$i]['host'];
1811 return [ $host, $maxLag, $maxIndex ];
1814 public function getLagTimes( $domain = false ) {
1815 if ( $this->getServerCount() <= 1 ) {
1816 return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1819 $knownLagTimes = []; // map of (server index => 0 seconds)
1820 $indexesWithLag = [];
1821 foreach ( $this->servers
as $i => $server ) {
1822 if ( empty( $server['is static'] ) ) {
1823 $indexesWithLag[] = $i; // DB server might have replication lag
1825 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1829 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) +
$knownLagTimes;
1832 public function safeGetLag( IDatabase
$conn ) {
1833 if ( $this->getServerCount() <= 1 ) {
1836 return $conn->getLag();
1841 * @param IDatabase $conn
1842 * @param DBMasterPos|bool $pos
1843 * @param int|null $timeout
1846 public function safeWaitForMasterPos( IDatabase
$conn, $pos = false, $timeout = null ) {
1847 $timeout = max( 1, $timeout ?
: $this->waitTimeout
);
1849 if ( $this->getServerCount() <= 1 ||
!$conn->getLBInfo( 'replica' ) ) {
1850 return true; // server is not a replica DB
1854 // Get the current master position, opening a connection if needed
1855 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1856 if ( $masterConn ) {
1857 $pos = $masterConn->getMasterPos();
1859 $masterConn = $this->openConnection( $this->getWriterIndex(), self
::DOMAIN_ANY
);
1860 $pos = $masterConn->getMasterPos();
1861 $this->closeConnection( $masterConn );
1865 if ( $pos instanceof DBMasterPos
) {
1866 $result = $conn->masterPosWait( $pos, $timeout );
1867 if ( $result == -1 ||
is_null( $result ) ) {
1868 $msg = __METHOD__
. ': timed out waiting on {host} pos {pos}';
1869 $this->replLogger
->warning( $msg, [
1870 'host' => $conn->getServer(),
1872 'trace' => ( new RuntimeException() )->getTraceAsString()
1876 $this->replLogger
->debug( __METHOD__
. ': done waiting' );
1880 $ok = false; // something is misconfigured
1881 $this->replLogger
->error(
1882 __METHOD__
. ': could not get master pos for {host}',
1884 'host' => $conn->getServer(),
1885 'trace' => ( new RuntimeException() )->getTraceAsString()
1893 public function setTransactionListener( $name, callable
$callback = null ) {
1895 $this->trxRecurringCallbacks
[$name] = $callback;
1897 unset( $this->trxRecurringCallbacks
[$name] );
1899 $this->forEachOpenMasterConnection(
1900 function ( IDatabase
$conn ) use ( $name, $callback ) {
1901 $conn->setTransactionListener( $name, $callback );
1906 public function setTableAliases( array $aliases ) {
1907 $this->tableAliases
= $aliases;
1910 public function setIndexAliases( array $aliases ) {
1911 $this->indexAliases
= $aliases;
1914 public function setDomainPrefix( $prefix ) {
1915 // Find connections to explicit foreign domains still marked as in-use...
1917 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$domainsInUse ) {
1918 // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1919 // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1920 if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1921 $domainsInUse[] = $conn->getDomainID();
1925 // Do not switch connections to explicit foreign domains unless marked as safe
1926 if ( $domainsInUse ) {
1927 $domains = implode( ', ', $domainsInUse );
1928 throw new DBUnexpectedError( null,
1929 "Foreign domain connections are still in use ($domains)." );
1932 $this->setLocalDomain( new DatabaseDomain(
1933 $this->localDomain
->getDatabase(),
1934 $this->localDomain
->getSchema(),
1938 // Update the prefix for all local connections...
1939 $this->forEachOpenConnection( function ( IDatabase
$db ) use ( $prefix ) {
1940 if ( !$db->getLBInfo( 'foreign' ) ) {
1941 $db->tablePrefix( $prefix );
1947 * @param DatabaseDomain $domain
1949 private function setLocalDomain( DatabaseDomain
$domain ) {
1950 $this->localDomain
= $domain;
1951 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
1952 // always true, gracefully handle the case when they fail to account for escaping.
1953 if ( $this->localDomain
->getTablePrefix() != '' ) {
1954 $this->localDomainIdAlias
=
1955 $this->localDomain
->getDatabase() . '-' . $this->localDomain
->getTablePrefix();
1957 $this->localDomainIdAlias
= $this->localDomain
->getDatabase();
1962 * Make PHP ignore user aborts/disconnects until the returned
1963 * value leaves scope. This returns null and does nothing in CLI mode.
1965 * @return ScopedCallback|null
1967 final protected function getScopedPHPBehaviorForCommit() {
1968 if ( PHP_SAPI
!= 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1969 $old = ignore_user_abort( true ); // avoid half-finished operations
1970 return new ScopedCallback( function () use ( $old ) {
1971 ignore_user_abort( $old );
1978 function __destruct() {
1979 // Avoid connection leaks for sanity
1985 * @deprecated since 1.29
1987 class_alias( LoadBalancer
::class, 'LoadBalancer' );