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 array[] Map of (server index => server config array) */
43 /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
45 /** @var float[] Map of (server index => weight) */
47 /** @var array[] Map of (group => server index => weight) */
49 /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
50 private $mAllowLagged;
51 /** @var int Seconds to spend waiting on replica DB lag to resolve */
52 private $mWaitTimeout;
53 /** @var array The LoadMonitor configuration */
54 private $loadMonitorConfig;
55 /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
56 private $tableAliases = [];
58 /** @var ILoadMonitor */
60 /** @var ChronologyProtector|null */
64 /** @var WANObjectCache */
66 /** @var object|string Class name or object With profileIn/profileOut methods */
68 /** @var TransactionProfiler */
69 protected $trxProfiler;
70 /** @var LoggerInterface */
71 protected $replLogger;
72 /** @var LoggerInterface */
73 protected $connLogger;
74 /** @var LoggerInterface */
75 protected $queryLogger;
76 /** @var LoggerInterface */
77 protected $perfLogger;
79 /** @var Database DB connection object that caused a problem */
80 private $errorConnection;
81 /** @var int The generic (not query grouped) replica DB index (of $mServers) */
83 /** @var bool|DBMasterPos False if not set */
85 /** @var bool Whether the generic reader fell back to a lagged replica DB */
86 private $laggedReplicaMode = false;
87 /** @var bool Whether the generic reader fell back to a lagged replica DB */
88 private $allReplicasDownMode = false;
89 /** @var string The last DB selection or connection error */
90 private $mLastError = 'Unknown error';
91 /** @var string|bool Reason the LB is read-only or false if not */
92 private $readOnlyReason = false;
93 /** @var int Total connections opened */
94 private $connsOpened = 0;
95 /** @var string|bool String if a requested DBO_TRX transaction round is active */
96 private $trxRoundId = false;
97 /** @var array[] Map of (name => callable) */
98 private $trxRecurringCallbacks = [];
99 /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
100 private $localDomain;
101 /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
102 private $localDomainIdAlias;
103 /** @var string Current server name */
105 /** @var bool Whether this PHP instance is for a CLI script */
107 /** @var string Agent name for query profiling */
110 /** @var callable Exception logger */
111 private $errorLogger;
114 private $disabled = false;
116 private $chronProtInitialized = false;
118 private $maxLag = self
::MAX_LAG_DEFAULT
;
120 /** @var int Warn when this many connection are held */
121 const CONN_HELD_WARN_THRESHOLD
= 10;
123 /** @var int Default 'maxLag' when unspecified */
124 const MAX_LAG_DEFAULT
= 10;
125 /** @var int Seconds to cache master server read-only status */
126 const TTL_CACHE_READONLY
= 5;
128 const KEY_LOCAL
= 'local';
129 const KEY_FOREIGN_FREE
= 'foreignFree';
130 const KEY_FOREIGN_INUSE
= 'foreignInUse';
132 const KEY_LOCAL_NOROUND
= 'localAutoCommit';
133 const KEY_FOREIGN_FREE_NOROUND
= 'foreignFreeAutoCommit';
134 const KEY_FOREIGN_INUSE_NOROUND
= 'foreignInUseAutoCommit';
136 public function __construct( array $params ) {
137 if ( !isset( $params['servers'] ) ) {
138 throw new InvalidArgumentException( __CLASS__
. ': missing servers parameter' );
140 $this->mServers
= $params['servers'];
141 foreach ( $this->mServers
as $i => $server ) {
143 $this->mServers
[$i]['master'] = true;
145 $this->mServers
[$i]['replica'] = true;
149 $localDomain = isset( $params['localDomain'] )
150 ? DatabaseDomain
::newFromId( $params['localDomain'] )
151 : DatabaseDomain
::newUnspecified();
152 $this->setLocalDomain( $localDomain );
154 $this->mWaitTimeout
= isset( $params['waitTimeout'] ) ?
$params['waitTimeout'] : 10;
156 $this->mReadIndex
= -1;
158 // Connection were transaction rounds may be applied
159 self
::KEY_LOCAL
=> [],
160 self
::KEY_FOREIGN_INUSE
=> [],
161 self
::KEY_FOREIGN_FREE
=> [],
162 // Auto-committing counterpart connections that ignore transaction rounds
163 self
::KEY_LOCAL_NOROUND
=> [],
164 self
::KEY_FOREIGN_INUSE_NOROUND
=> [],
165 self
::KEY_FOREIGN_FREE_NOROUND
=> []
168 $this->mWaitForPos
= false;
169 $this->mAllowLagged
= false;
171 if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
172 $this->readOnlyReason
= $params['readOnlyReason'];
175 if ( isset( $params['maxLag'] ) ) {
176 $this->maxLag
= $params['maxLag'];
179 if ( isset( $params['loadMonitor'] ) ) {
180 $this->loadMonitorConfig
= $params['loadMonitor'];
182 $this->loadMonitorConfig
= [ 'class' => 'LoadMonitorNull' ];
184 $this->loadMonitorConfig +
= [ 'lagWarnThreshold' => $this->maxLag
];
186 foreach ( $params['servers'] as $i => $server ) {
187 $this->mLoads
[$i] = $server['load'];
188 if ( isset( $server['groupLoads'] ) ) {
189 foreach ( $server['groupLoads'] as $group => $ratio ) {
190 if ( !isset( $this->mGroupLoads
[$group] ) ) {
191 $this->mGroupLoads
[$group] = [];
193 $this->mGroupLoads
[$group][$i] = $ratio;
198 if ( isset( $params['srvCache'] ) ) {
199 $this->srvCache
= $params['srvCache'];
201 $this->srvCache
= new EmptyBagOStuff();
203 if ( isset( $params['wanCache'] ) ) {
204 $this->wanCache
= $params['wanCache'];
206 $this->wanCache
= WANObjectCache
::newEmpty();
208 $this->profiler
= isset( $params['profiler'] ) ?
$params['profiler'] : null;
209 if ( isset( $params['trxProfiler'] ) ) {
210 $this->trxProfiler
= $params['trxProfiler'];
212 $this->trxProfiler
= new TransactionProfiler();
215 $this->errorLogger
= isset( $params['errorLogger'] )
216 ?
$params['errorLogger']
217 : function ( Exception
$e ) {
218 trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING
);
221 foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
222 $this->$key = isset( $params[$key] ) ?
$params[$key] : new NullLogger();
225 $this->host
= isset( $params['hostname'] )
226 ?
$params['hostname']
227 : ( gethostname() ?
: 'unknown' );
228 $this->cliMode
= isset( $params['cliMode'] )
230 : ( PHP_SAPI
=== 'cli' || PHP_SAPI
=== 'phpdbg' );
231 $this->agent
= isset( $params['agent'] ) ?
$params['agent'] : '';
233 if ( isset( $params['chronologyProtector'] ) ) {
234 $this->chronProt
= $params['chronologyProtector'];
239 * Get the local (and default) database domain ID of connection handles
241 * @see DatabaseDomain
242 * @return string Database domain ID; this specifies DB name, schema, and table prefix
245 public function getLocalDomainID() {
246 return $this->localDomain
->getId();
250 * Get a LoadMonitor instance
252 * @return ILoadMonitor
254 private function getLoadMonitor() {
255 if ( !isset( $this->loadMonitor
) ) {
257 'LoadMonitor' => LoadMonitor
::class,
258 'LoadMonitorNull' => LoadMonitorNull
::class,
259 'LoadMonitorMySQL' => LoadMonitorMySQL
::class,
262 $class = $this->loadMonitorConfig
['class'];
263 if ( isset( $compat[$class] ) ) {
264 $class = $compat[$class];
267 $this->loadMonitor
= new $class(
268 $this, $this->srvCache
, $this->wanCache
, $this->loadMonitorConfig
);
269 $this->loadMonitor
->setLogger( $this->replLogger
);
272 return $this->loadMonitor
;
276 * @param array $loads
277 * @param bool|string $domain Domain to get non-lagged for
278 * @param int $maxLag Restrict the maximum allowed lag to this many seconds
279 * @return bool|int|string
281 private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF
) {
282 $lags = $this->getLagTimes( $domain );
284 # Unset excessively lagged servers
285 foreach ( $lags as $i => $lag ) {
287 # How much lag this server nominally is allowed to have
288 $maxServerLag = isset( $this->mServers
[$i]['max lag'] )
289 ?
$this->mServers
[$i]['max lag']
290 : $this->maxLag
; // default
291 # Constrain that futher by $maxLag argument
292 $maxServerLag = min( $maxServerLag, $maxLag );
294 $host = $this->getServerName( $i );
295 if ( $lag === false && !is_infinite( $maxServerLag ) ) {
296 $this->replLogger
->error(
297 "Server {host} is not replicating?", [ 'host' => $host ] );
299 } elseif ( $lag > $maxServerLag ) {
300 $this->replLogger
->info(
301 "Server {host} has {lag} seconds of lag (>= {maxlag})",
302 [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
309 # Find out if all the replica DBs with non-zero load are lagged
311 foreach ( $loads as $load ) {
315 # No appropriate DB servers except maybe the master and some replica DBs with zero load
316 # Do NOT use the master
317 # Instead, this function will return false, triggering read-only mode,
318 # and a lagged replica DB will be used instead.
322 if ( count( $loads ) == 0 ) {
326 # Return a random representative of the remainder
327 return ArrayUtils
::pickRandom( $loads );
330 public function getReaderIndex( $group = false, $domain = false ) {
331 if ( count( $this->mServers
) == 1 ) {
332 // Skip the load balancing if there's only one server
333 return $this->getWriterIndex();
334 } elseif ( $group === false && $this->mReadIndex
>= 0 ) {
335 // Shortcut if the generic reader index was already cached
336 return $this->mReadIndex
;
339 if ( $group !== false ) {
340 // Use the server weight array for this load group
341 if ( isset( $this->mGroupLoads
[$group] ) ) {
342 $loads = $this->mGroupLoads
[$group];
344 // No loads for this group, return false and the caller can use some other group
345 $this->connLogger
->info( __METHOD__
. ": no loads for group $group" );
350 // Use the generic load group
351 $loads = $this->mLoads
;
354 // Scale the configured load ratios according to each server's load and state
355 $this->getLoadMonitor()->scaleLoads( $loads, $domain );
357 // Pick a server to use, accounting for weights, load, lag, and mWaitForPos
358 list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
359 if ( $i === false ) {
360 // Replica DB connection unsuccessful
364 if ( $this->mWaitForPos
&& $i != $this->getWriterIndex() ) {
365 // Before any data queries are run, wait for the server to catch up to the
366 // specified position. This is used to improve session consistency. Note that
367 // when LoadBalancer::waitFor() sets mWaitForPos, the waiting triggers here,
368 // so update laggedReplicaMode as needed for consistency.
369 if ( !$this->doWait( $i ) ) {
370 $laggedReplicaMode = true;
374 if ( $this->mReadIndex
<= 0 && $this->mLoads
[$i] > 0 && $group === false ) {
375 // Cache the generic reader index for future ungrouped DB_REPLICA handles
376 $this->mReadIndex
= $i;
377 // Record if the generic reader index is in "lagged replica DB" mode
378 if ( $laggedReplicaMode ) {
379 $this->laggedReplicaMode
= true;
383 $serverName = $this->getServerName( $i );
384 $this->connLogger
->debug( __METHOD__
. ": using server $serverName for group '$group'" );
390 * @param array $loads List of server weights
391 * @param string|bool $domain
392 * @return array (reader index, lagged replica mode) or false on failure
394 private function pickReaderIndex( array $loads, $domain = false ) {
395 if ( !count( $loads ) ) {
396 throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
399 /** @var int|bool $i Index of selected server */
401 /** @var bool $laggedReplicaMode Whether server is considered lagged */
402 $laggedReplicaMode = false;
404 // Quickly look through the available servers for a server that meets criteria...
405 $currentLoads = $loads;
406 while ( count( $currentLoads ) ) {
407 if ( $this->mAllowLagged ||
$laggedReplicaMode ) {
408 $i = ArrayUtils
::pickRandom( $currentLoads );
411 if ( $this->mWaitForPos
&& $this->mWaitForPos
->asOfTime() ) {
412 // ChronologyProtecter sets mWaitForPos for session consistency.
413 // This triggers doWait() after connect, so it's especially good to
414 // avoid lagged servers so as to avoid excessive delay in that method.
415 $ago = microtime( true ) - $this->mWaitForPos
->asOfTime();
416 // Aim for <= 1 second of waiting (being too picky can backfire)
417 $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago +
1 );
419 if ( $i === false ) {
420 // Any server with less lag than it's 'max lag' param is preferable
421 $i = $this->getRandomNonLagged( $currentLoads, $domain );
423 if ( $i === false && count( $currentLoads ) != 0 ) {
424 // All replica DBs lagged. Switch to read-only mode
425 $this->replLogger
->error( "All replica DBs lagged. Switch to read-only mode" );
426 $i = ArrayUtils
::pickRandom( $currentLoads );
427 $laggedReplicaMode = true;
431 if ( $i === false ) {
432 // pickRandom() returned false.
433 // This is permanent and means the configuration or the load monitor
434 // wants us to return false.
435 $this->connLogger
->debug( __METHOD__
. ": pickRandom() returned false" );
437 return [ false, false ];
440 $serverName = $this->getServerName( $i );
441 $this->connLogger
->debug( __METHOD__
. ": Using reader #$i: $serverName..." );
443 $conn = $this->openConnection( $i, $domain );
445 $this->connLogger
->warning( __METHOD__
. ": Failed connecting to $i/$domain" );
446 unset( $currentLoads[$i] ); // avoid this server next iteration
451 // Decrement reference counter, we are finished with this connection.
452 // It will be incremented for the caller later.
453 if ( $domain !== false ) {
454 $this->reuseConnection( $conn );
457 // Return this server
461 // If all servers were down, quit now
462 if ( !count( $currentLoads ) ) {
463 $this->connLogger
->error( "All servers down" );
466 return [ $i, $laggedReplicaMode ];
469 public function waitFor( $pos ) {
470 $oldPos = $this->mWaitForPos
;
472 $this->mWaitForPos
= $pos;
473 // If a generic reader connection was already established, then wait now
474 $i = $this->mReadIndex
;
476 if ( !$this->doWait( $i ) ) {
477 $this->laggedReplicaMode
= true;
481 // Restore the older position if it was higher since this is used for lag-protection
482 $this->setWaitForPositionIfHigher( $oldPos );
486 public function waitForOne( $pos, $timeout = null ) {
487 $oldPos = $this->mWaitForPos
;
489 $this->mWaitForPos
= $pos;
491 $i = $this->mReadIndex
;
493 // Pick a generic replica DB if there isn't one yet
494 $readLoads = $this->mLoads
;
495 unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
496 $readLoads = array_filter( $readLoads ); // with non-zero load
497 $i = ArrayUtils
::pickRandom( $readLoads );
501 $ok = $this->doWait( $i, true, $timeout );
503 $ok = true; // no applicable loads
506 # Restore the old position, as this is not used for lag-protection but for throttling
507 $this->mWaitForPos
= $oldPos;
513 public function waitForAll( $pos, $timeout = null ) {
514 $timeout = $timeout ?
: $this->mWaitTimeout
;
516 $oldPos = $this->mWaitForPos
;
518 $this->mWaitForPos
= $pos;
519 $serverCount = count( $this->mServers
);
522 for ( $i = 1; $i < $serverCount; $i++
) {
523 if ( $this->mLoads
[$i] > 0 ) {
524 $start = microtime( true );
525 $ok = $this->doWait( $i, true, max( 1, (int)$timeout ) ) && $ok;
526 $timeout -= ( microtime( true ) - $start );
527 if ( $timeout <= 0 ) {
528 break; // timeout reached
533 # Restore the old position, as this is not used for lag-protection but for throttling
534 $this->mWaitForPos
= $oldPos;
541 * @param DBMasterPos|bool $pos
543 private function setWaitForPositionIfHigher( $pos ) {
548 if ( !$this->mWaitForPos ||
$pos->hasReached( $this->mWaitForPos
) ) {
549 $this->mWaitForPos
= $pos;
555 * @return IDatabase|bool
557 public function getAnyOpenConnection( $i ) {
558 foreach ( $this->mConns
as $connsByServer ) {
559 if ( !empty( $connsByServer[$i] ) ) {
560 /** @var IDatabase[] $serverConns */
561 $serverConns = $connsByServer[$i];
563 return reset( $serverConns );
571 * Wait for a given replica DB to catch up to the master pos stored in $this
572 * @param int $index Server index
573 * @param bool $open Check the server even if a new connection has to be made
574 * @param int $timeout Max seconds to wait; default is mWaitTimeout
577 protected function doWait( $index, $open = false, $timeout = null ) {
578 $close = false; // close the connection afterwards
580 // Check if we already know that the DB has reached this point
581 $server = $this->getServerName( $index );
582 $key = $this->srvCache
->makeGlobalKey( __CLASS__
, 'last-known-pos', $server, 'v1' );
583 /** @var DBMasterPos $knownReachedPos */
584 $knownReachedPos = $this->srvCache
->get( $key );
586 $knownReachedPos instanceof DBMasterPos
&&
587 $knownReachedPos->hasReached( $this->mWaitForPos
)
589 $this->replLogger
->debug( __METHOD__
.
590 ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).',
591 [ 'dbserver' => $server ] );
595 // Find a connection to wait on, creating one if needed and allowed
596 $conn = $this->getAnyOpenConnection( $index );
599 $this->replLogger
->debug( __METHOD__
. ': no connection open for {dbserver}',
600 [ 'dbserver' => $server ] );
604 $conn = $this->openConnection( $index, self
::DOMAIN_ANY
);
606 $this->replLogger
->warning( __METHOD__
. ': failed to connect to {dbserver}',
607 [ 'dbserver' => $server ] );
611 // Avoid connection spam in waitForAll() when connections
612 // are made just for the sake of doing this lag check.
617 $this->replLogger
->info( __METHOD__
. ': Waiting for replica DB {dbserver} to catch up...',
618 [ 'dbserver' => $server ] );
619 $timeout = $timeout ?
: $this->mWaitTimeout
;
620 $result = $conn->masterPosWait( $this->mWaitForPos
, $timeout );
622 if ( $result == -1 ||
is_null( $result ) ) {
623 // Timed out waiting for replica DB, use master instead
624 $this->replLogger
->warning(
625 __METHOD__
. ': Timed out waiting on {host} pos {pos}',
626 [ 'host' => $server, 'pos' => $this->mWaitForPos
]
630 $this->replLogger
->info( __METHOD__
. ": Done" );
632 // Remember that the DB reached this point
633 $this->srvCache
->set( $key, $this->mWaitForPos
, BagOStuff
::TTL_DAY
);
637 $this->closeConnection( $conn );
643 public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
644 if ( $i === null ||
$i === false ) {
645 throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__
.
646 ' with invalid server index' );
649 if ( $this->localDomain
->equals( $domain ) ||
$domain === $this->localDomainIdAlias
) {
650 $domain = false; // local connection requested
653 $groups = ( $groups === false ||
$groups === [] )
654 ?
[ false ] // check one "group": the generic pool
657 $masterOnly = ( $i == self
::DB_MASTER ||
$i == $this->getWriterIndex() );
658 $oldConnsOpened = $this->connsOpened
; // connections open now
660 if ( $i == self
::DB_MASTER
) {
661 $i = $this->getWriterIndex();
663 # Try to find an available server in any the query groups (in order)
664 foreach ( $groups as $group ) {
665 $groupIndex = $this->getReaderIndex( $group, $domain );
666 if ( $groupIndex !== false ) {
673 # Operation-based index
674 if ( $i == self
::DB_REPLICA
) {
675 $this->mLastError
= 'Unknown error'; // reset error string
676 # Try the general server pool if $groups are unavailable.
677 $i = ( $groups === [ false ] )
678 ?
false // don't bother with this if that is what was tried above
679 : $this->getReaderIndex( false, $domain );
680 # Couldn't find a working server in getReaderIndex()?
681 if ( $i === false ) {
682 $this->mLastError
= 'No working replica DB server: ' . $this->mLastError
;
683 // Throw an exception
684 $this->reportConnectionError();
685 return null; // not reached
689 # Now we have an explicit index into the servers array
690 $conn = $this->openConnection( $i, $domain, $flags );
692 // Throw an exception
693 $this->reportConnectionError();
694 return null; // not reached
697 # Profile any new connections that happen
698 if ( $this->connsOpened
> $oldConnsOpened ) {
699 $host = $conn->getServer();
700 $dbname = $conn->getDBname();
701 $this->trxProfiler
->recordConnection( $host, $dbname, $masterOnly );
705 # Make master-requested DB handles inherit any read-only mode setting
706 $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
712 public function reuseConnection( $conn ) {
713 $serverIndex = $conn->getLBInfo( 'serverIndex' );
714 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
715 if ( $serverIndex === null ||
$refCount === null ) {
717 * This can happen in code like:
718 * foreach ( $dbs as $db ) {
719 * $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
721 * $lb->reuseConnection( $conn );
723 * When a connection to the local DB is opened in this way, reuseConnection()
727 } elseif ( $conn instanceof DBConnRef
) {
728 // DBConnRef already handles calling reuseConnection() and only passes the live
729 // Database instance to this method. Any caller passing in a DBConnRef is broken.
730 $this->connLogger
->error( __METHOD__
. ": got DBConnRef instance.\n" .
731 ( new RuntimeException() )->getTraceAsString() );
736 if ( $this->disabled
) {
737 return; // DBConnRef handle probably survived longer than the LoadBalancer
740 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
741 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
742 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
744 $connFreeKey = self
::KEY_FOREIGN_FREE
;
745 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
748 $domain = $conn->getDomainID();
749 if ( !isset( $this->mConns
[$connInUseKey][$serverIndex][$domain] ) ) {
750 throw new InvalidArgumentException( __METHOD__
.
751 ": connection $serverIndex/$domain not found; it may have already been freed." );
752 } elseif ( $this->mConns
[$connInUseKey][$serverIndex][$domain] !== $conn ) {
753 throw new InvalidArgumentException( __METHOD__
.
754 ": connection $serverIndex/$domain mismatched; it may have already been freed." );
757 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
758 if ( $refCount <= 0 ) {
759 $this->mConns
[$connFreeKey][$serverIndex][$domain] = $conn;
760 unset( $this->mConns
[$connInUseKey][$serverIndex][$domain] );
761 if ( !$this->mConns
[$connInUseKey][$serverIndex] ) {
762 unset( $this->mConns
[$connInUseKey][$serverIndex] ); // clean up
764 $this->connLogger
->debug( __METHOD__
. ": freed connection $serverIndex/$domain" );
766 $this->connLogger
->debug( __METHOD__
.
767 ": reference count for $serverIndex/$domain reduced to $refCount" );
771 public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
772 $domain = ( $domain !== false ) ?
$domain : $this->localDomain
;
774 return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
777 public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
778 $domain = ( $domain !== false ) ?
$domain : $this->localDomain
;
780 return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
783 public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
784 $domain = ( $domain !== false ) ?
$domain : $this->localDomain
;
786 return new MaintainableDBConnRef(
787 $this, $this->getConnection( $db, $groups, $domain, $flags ) );
790 public function openConnection( $i, $domain = false, $flags = 0 ) {
791 if ( $this->localDomain
->equals( $domain ) ||
$domain === $this->localDomainIdAlias
) {
792 $domain = false; // local connection requested
795 if ( !$this->chronProtInitialized
&& $this->chronProt
) {
796 $this->connLogger
->debug( __METHOD__
. ': calling initLB() before first connection.' );
797 // Load CP positions before connecting so that doWait() triggers later if needed
798 $this->chronProtInitialized
= true;
799 $this->chronProt
->initLB( $this );
802 // Check if an auto-commit connection is being requested. If so, it will not reuse the
803 // main set of DB connections but rather its own pool since:
804 // a) those are usually set to implicitly use transaction rounds via DBO_TRX
805 // b) those must support the use of explicit transaction rounds via beginMasterChanges()
806 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTO
) == self
::CONN_TRX_AUTO
);
808 if ( $domain !== false ) {
809 // Connection is to a foreign domain
810 $conn = $this->openForeignConnection( $i, $domain, $flags );
812 // Connection is to the local domain
813 $connKey = $autoCommit ? self
::KEY_LOCAL_NOROUND
: self
::KEY_LOCAL
;
814 if ( isset( $this->mConns
[$connKey][$i][0] ) ) {
815 $conn = $this->mConns
[$connKey][$i][0];
817 if ( !isset( $this->mServers
[$i] ) ||
!is_array( $this->mServers
[$i] ) ) {
818 throw new InvalidArgumentException( "No server with index '$i'." );
820 // Open a new connection
821 $server = $this->mServers
[$i];
822 $server['serverIndex'] = $i;
823 $server['autoCommitOnly'] = $autoCommit;
824 if ( $this->localDomain
->getDatabase() !== null ) {
825 // Use the local domain table prefix if the local domain is specified
826 $server['tablePrefix'] = $this->localDomain
->getTablePrefix();
828 $conn = $this->reallyOpenConnection( $server, $this->localDomain
);
829 $host = $this->getServerName( $i );
830 if ( $conn->isOpen() ) {
831 $this->connLogger
->debug( "Connected to database $i at '$host'." );
832 $this->mConns
[$connKey][$i][0] = $conn;
834 $this->connLogger
->warning( "Failed to connect to database $i at '$host'." );
835 $this->errorConnection
= $conn;
841 if ( $conn instanceof IDatabase
&& !$conn->isOpen() ) {
842 // Connection was made but later unrecoverably lost for some reason.
843 // Do not return a handle that will just throw exceptions on use,
844 // but let the calling code (e.g. getReaderIndex) try another server.
845 // See DatabaseMyslBase::ping() for how this can happen.
846 $this->errorConnection
= $conn;
850 if ( $autoCommit && $conn instanceof IDatabase
) {
851 $conn->clearFlag( $conn::DBO_TRX
); // auto-commit mode
858 * Open a connection to a foreign DB, or return one if it is already open.
860 * Increments a reference count on the returned connection which locks the
861 * connection to the requested domain. This reference count can be
862 * decremented by calling reuseConnection().
864 * If a connection is open to the appropriate server already, but with the wrong
865 * database, it will be switched to the right database and returned, as long as
866 * it has been freed first with reuseConnection().
868 * On error, returns false, and the connection which caused the
869 * error will be available via $this->errorConnection.
871 * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
873 * @param int $i Server index
874 * @param string $domain Domain ID to open
875 * @param int $flags Class CONN_* constant bitfield
878 private function openForeignConnection( $i, $domain, $flags = 0 ) {
879 $domainInstance = DatabaseDomain
::newFromId( $domain );
880 $dbName = $domainInstance->getDatabase();
881 $prefix = $domainInstance->getTablePrefix();
882 $autoCommit = ( ( $flags & self
::CONN_TRX_AUTO
) == self
::CONN_TRX_AUTO
);
885 $connFreeKey = self
::KEY_FOREIGN_FREE_NOROUND
;
886 $connInUseKey = self
::KEY_FOREIGN_INUSE_NOROUND
;
888 $connFreeKey = self
::KEY_FOREIGN_FREE
;
889 $connInUseKey = self
::KEY_FOREIGN_INUSE
;
892 if ( isset( $this->mConns
[$connInUseKey][$i][$domain] ) ) {
893 // Reuse an in-use connection for the same domain
894 $conn = $this->mConns
[$connInUseKey][$i][$domain];
895 $this->connLogger
->debug( __METHOD__
. ": reusing connection $i/$domain" );
896 } elseif ( isset( $this->mConns
[$connFreeKey][$i][$domain] ) ) {
897 // Reuse a free connection for the same domain
898 $conn = $this->mConns
[$connFreeKey][$i][$domain];
899 unset( $this->mConns
[$connFreeKey][$i][$domain] );
900 $this->mConns
[$connInUseKey][$i][$domain] = $conn;
901 $this->connLogger
->debug( __METHOD__
. ": reusing free connection $i/$domain" );
902 } elseif ( !empty( $this->mConns
[$connFreeKey][$i] ) ) {
903 // Reuse a free connection from another domain
904 $conn = reset( $this->mConns
[$connFreeKey][$i] );
905 $oldDomain = key( $this->mConns
[$connFreeKey][$i] );
906 if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
907 $this->mLastError
= "Error selecting database '$dbName' on server " .
908 $conn->getServer() . " from client host {$this->host}";
909 $this->errorConnection
= $conn;
912 $conn->tablePrefix( $prefix );
913 unset( $this->mConns
[$connFreeKey][$i][$oldDomain] );
914 // Note that if $domain is an empty string, getDomainID() might not match it
915 $this->mConns
[$connInUseKey][$i][$conn->getDomainId()] = $conn;
916 $this->connLogger
->debug( __METHOD__
.
917 ": reusing free connection from $oldDomain for $domain" );
920 if ( !isset( $this->mServers
[$i] ) ||
!is_array( $this->mServers
[$i] ) ) {
921 throw new InvalidArgumentException( "No server with index '$i'." );
923 // Open a new connection
924 $server = $this->mServers
[$i];
925 $server['serverIndex'] = $i;
926 $server['foreignPoolRefCount'] = 0;
927 $server['foreign'] = true;
928 $server['autoCommitOnly'] = $autoCommit;
929 $conn = $this->reallyOpenConnection( $server, $domainInstance );
930 if ( !$conn->isOpen() ) {
931 $this->connLogger
->warning( __METHOD__
. ": connection error for $i/$domain" );
932 $this->errorConnection
= $conn;
935 $conn->tablePrefix( $prefix ); // as specified
936 // Note that if $domain is an empty string, getDomainID() might not match it
937 $this->mConns
[$connInUseKey][$i][$conn->getDomainID()] = $conn;
938 $this->connLogger
->debug( __METHOD__
. ": opened new connection for $i/$domain" );
942 // Increment reference count
943 if ( $conn instanceof IDatabase
) {
944 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
945 $conn->setLBInfo( 'foreignPoolRefCount', $refCount +
1 );
952 * Test if the specified index represents an open connection
954 * @param int $index Server index
958 private function isOpen( $index ) {
959 if ( !is_int( $index ) ) {
963 return (bool)$this->getAnyOpenConnection( $index );
967 * Open a new network connection to a server (uncached)
969 * Returns a Database object whether or not the connection was successful.
971 * @param array $server
972 * @param DatabaseDomain $domainOverride Use an unspecified domain to not select any database
974 * @throws DBAccessError
975 * @throws InvalidArgumentException
977 protected function reallyOpenConnection( array $server, DatabaseDomain
$domainOverride ) {
978 if ( $this->disabled
) {
979 throw new DBAccessError();
982 if ( $domainOverride->getDatabase() !== null ) {
983 $server['dbname'] = $domainOverride->getDatabase();
984 $server['schema'] = $domainOverride->getSchema();
987 // Let the handle know what the cluster master is (e.g. "db1052")
988 $masterName = $this->getServerName( $this->getWriterIndex() );
989 $server['clusterMasterHost'] = $masterName;
991 // Log when many connection are made on requests
992 if ( ++
$this->connsOpened
>= self
::CONN_HELD_WARN_THRESHOLD
) {
993 $this->perfLogger
->warning( __METHOD__
. ": " .
994 "{$this->connsOpened}+ connections made (master=$masterName)" );
997 $server['srvCache'] = $this->srvCache
;
998 // Set loggers and profilers
999 $server['connLogger'] = $this->connLogger
;
1000 $server['queryLogger'] = $this->queryLogger
;
1001 $server['errorLogger'] = $this->errorLogger
;
1002 $server['profiler'] = $this->profiler
;
1003 $server['trxProfiler'] = $this->trxProfiler
;
1004 // Use the same agent and PHP mode for all DB handles
1005 $server['cliMode'] = $this->cliMode
;
1006 $server['agent'] = $this->agent
;
1007 // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
1008 // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
1009 $server['flags'] = isset( $server['flags'] ) ?
$server['flags'] : IDatabase
::DBO_DEFAULT
;
1011 // Create a live connection object
1013 $db = Database
::factory( $server['type'], $server );
1014 } catch ( DBConnectionError
$e ) {
1015 // FIXME: This is probably the ugliest thing I have ever done to
1016 // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
1020 $db->setLBInfo( $server );
1021 $db->setLazyMasterHandle(
1022 $this->getLazyConnectionRef( self
::DB_MASTER
, [], $db->getDomainID() )
1024 $db->setTableAliases( $this->tableAliases
);
1026 if ( $server['serverIndex'] === $this->getWriterIndex() ) {
1027 if ( $this->trxRoundId
!== false ) {
1028 $this->applyTransactionRoundFlags( $db );
1030 foreach ( $this->trxRecurringCallbacks
as $name => $callback ) {
1031 $db->setTransactionListener( $name, $callback );
1039 * @throws DBConnectionError
1041 private function reportConnectionError() {
1042 $conn = $this->errorConnection
; // the connection which caused the error
1044 'method' => __METHOD__
,
1045 'last_error' => $this->mLastError
,
1048 if ( $conn instanceof IDatabase
) {
1049 $context['db_server'] = $conn->getServer();
1050 $this->connLogger
->warning(
1051 "Connection error: {last_error} ({db_server})",
1055 // throws DBConnectionError
1056 $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
1058 // No last connection, probably due to all servers being too busy
1059 $this->connLogger
->error(
1060 "LB failure with no last connection. Connection error: {last_error}",
1064 // If all servers were busy, mLastError will contain something sensible
1065 throw new DBConnectionError( null, $this->mLastError
);
1069 public function getWriterIndex() {
1073 public function haveIndex( $i ) {
1074 return array_key_exists( $i, $this->mServers
);
1077 public function isNonZeroLoad( $i ) {
1078 return array_key_exists( $i, $this->mServers
) && $this->mLoads
[$i] != 0;
1081 public function getServerCount() {
1082 return count( $this->mServers
);
1085 public function getServerName( $i ) {
1086 if ( isset( $this->mServers
[$i]['hostName'] ) ) {
1087 $name = $this->mServers
[$i]['hostName'];
1088 } elseif ( isset( $this->mServers
[$i]['host'] ) ) {
1089 $name = $this->mServers
[$i]['host'];
1094 return ( $name != '' ) ?
$name : 'localhost';
1097 public function getServerType( $i ) {
1098 return isset( $this->mServers
[$i]['type'] ) ?
$this->mServers
[$i]['type'] : 'unknown';
1101 public function getMasterPos() {
1102 # If this entire request was served from a replica DB without opening a connection to the
1103 # master (however unlikely that may be), then we can fetch the position from the replica DB.
1104 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1105 if ( !$masterConn ) {
1106 $serverCount = count( $this->mServers
);
1107 for ( $i = 1; $i < $serverCount; $i++
) {
1108 $conn = $this->getAnyOpenConnection( $i );
1110 return $conn->getReplicaPos();
1114 return $masterConn->getMasterPos();
1120 public function disable() {
1122 $this->disabled
= true;
1125 public function closeAll() {
1126 $this->forEachOpenConnection( function ( IDatabase
$conn ) {
1127 $host = $conn->getServer();
1128 $this->connLogger
->debug( "Closing connection to database '$host'." );
1133 self
::KEY_LOCAL
=> [],
1134 self
::KEY_FOREIGN_INUSE
=> [],
1135 self
::KEY_FOREIGN_FREE
=> [],
1136 self
::KEY_LOCAL_NOROUND
=> [],
1137 self
::KEY_FOREIGN_INUSE_NOROUND
=> [],
1138 self
::KEY_FOREIGN_FREE_NOROUND
=> []
1140 $this->connsOpened
= 0;
1143 public function closeConnection( IDatabase
$conn ) {
1144 $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
1145 foreach ( $this->mConns
as $type => $connsByServer ) {
1146 if ( !isset( $connsByServer[$serverIndex] ) ) {
1150 foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
1151 if ( $conn === $trackedConn ) {
1152 $host = $this->getServerName( $i );
1153 $this->connLogger
->debug( "Closing connection to database $i at '$host'." );
1154 unset( $this->mConns
[$type][$serverIndex][$i] );
1155 --$this->connsOpened
;
1164 public function commitAll( $fname = __METHOD__
) {
1167 $restore = ( $this->trxRoundId
!== false );
1168 $this->trxRoundId
= false;
1169 $this->forEachOpenConnection(
1170 function ( IDatabase
$conn ) use ( $fname, $restore, &$failures ) {
1172 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1173 } catch ( DBError
$e ) {
1174 call_user_func( $this->errorLogger
, $e );
1175 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1177 if ( $restore && $conn->getLBInfo( 'master' ) ) {
1178 $this->undoTransactionRoundFlags( $conn );
1184 throw new DBExpectedError(
1186 "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1191 public function finalizeMasterChanges() {
1192 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1193 // Any error should cause all DB transactions to be rolled back together
1194 $conn->setTrxEndCallbackSuppression( false );
1195 $conn->runOnTransactionPreCommitCallbacks();
1196 // Defer post-commit callbacks until COMMIT finishes for all DBs
1197 $conn->setTrxEndCallbackSuppression( true );
1201 public function approveMasterChanges( array $options ) {
1202 $limit = isset( $options['maxWriteDuration'] ) ?
$options['maxWriteDuration'] : 0;
1203 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( $limit ) {
1204 // If atomic sections or explicit transactions are still open, some caller must have
1205 // caught an exception but failed to properly rollback any changes. Detect that and
1206 // throw and error (causing rollback).
1207 if ( $conn->explicitTrxActive() ) {
1208 throw new DBTransactionError(
1210 "Explicit transaction still active. A caller may have caught an error."
1213 // Assert that the time to replicate the transaction will be sane.
1214 // If this fails, then all DB transactions will be rollback back together.
1215 $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY
);
1216 if ( $limit > 0 && $time > $limit ) {
1217 throw new DBTransactionSizeError(
1219 "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
1223 // If a connection sits idle while slow queries execute on another, that connection
1224 // may end up dropped before the commit round is reached. Ping servers to detect this.
1225 if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
1226 throw new DBTransactionError(
1228 "A connection to the {$conn->getDBname()} database was lost before commit."
1234 public function beginMasterChanges( $fname = __METHOD__
) {
1235 if ( $this->trxRoundId
!== false ) {
1236 throw new DBTransactionError(
1238 "$fname: Transaction round '{$this->trxRoundId}' already started."
1241 $this->trxRoundId
= $fname;
1244 $this->forEachOpenMasterConnection(
1245 function ( Database
$conn ) use ( $fname, &$failures ) {
1246 $conn->setTrxEndCallbackSuppression( true );
1248 $conn->flushSnapshot( $fname );
1249 } catch ( DBError
$e ) {
1250 call_user_func( $this->errorLogger
, $e );
1251 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1253 $conn->setTrxEndCallbackSuppression( false );
1254 $this->applyTransactionRoundFlags( $conn );
1259 throw new DBExpectedError(
1261 "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
1266 public function commitMasterChanges( $fname = __METHOD__
) {
1269 /** @noinspection PhpUnusedLocalVariableInspection */
1270 $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
1272 $restore = ( $this->trxRoundId
!== false );
1273 $this->trxRoundId
= false;
1274 $this->forEachOpenMasterConnection(
1275 function ( IDatabase
$conn ) use ( $fname, $restore, &$failures ) {
1277 if ( $conn->writesOrCallbacksPending() ) {
1278 $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS
);
1279 } elseif ( $restore ) {
1280 $conn->flushSnapshot( $fname );
1282 } catch ( DBError
$e ) {
1283 call_user_func( $this->errorLogger
, $e );
1284 $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
1287 $this->undoTransactionRoundFlags( $conn );
1293 throw new DBExpectedError(
1295 "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
1300 public function runMasterPostTrxCallbacks( $type ) {
1301 $e = null; // first exception
1302 $this->forEachOpenMasterConnection( function ( Database
$conn ) use ( $type, &$e ) {
1303 $conn->setTrxEndCallbackSuppression( false );
1304 if ( $conn->writesOrCallbacksPending() ) {
1305 // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
1306 // (which finished its callbacks already). Warn and recover in this case. Let the
1307 // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
1308 $this->queryLogger
->info( __METHOD__
. ": found writes/callbacks pending." );
1310 } elseif ( $conn->trxLevel() ) {
1311 // This happens for single-DB setups where DB_REPLICA uses the master DB,
1312 // thus leaving an implicit read-only transaction open at this point. It
1313 // also happens if onTransactionIdle() callbacks leave implicit transactions
1314 // open on *other* DBs (which is slightly improper). Let these COMMIT on the
1315 // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
1319 $conn->runOnTransactionIdleCallbacks( $type );
1320 } catch ( Exception
$ex ) {
1324 $conn->runTransactionListenerCallbacks( $type );
1325 } catch ( Exception
$ex ) {
1333 public function rollbackMasterChanges( $fname = __METHOD__
) {
1334 $restore = ( $this->trxRoundId
!== false );
1335 $this->trxRoundId
= false;
1336 $this->forEachOpenMasterConnection(
1337 function ( IDatabase
$conn ) use ( $fname, $restore ) {
1338 if ( $conn->writesOrCallbacksPending() ) {
1339 $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS
);
1342 $this->undoTransactionRoundFlags( $conn );
1348 public function suppressTransactionEndCallbacks() {
1349 $this->forEachOpenMasterConnection( function ( Database
$conn ) {
1350 $conn->setTrxEndCallbackSuppression( true );
1355 * @param IDatabase $conn
1357 private function applyTransactionRoundFlags( IDatabase
$conn ) {
1358 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1359 return; // transaction rounds do not apply to these connections
1362 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1363 // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
1364 // Force DBO_TRX even in CLI mode since a commit round is expected soon.
1365 $conn->setFlag( $conn::DBO_TRX
, $conn::REMEMBER_PRIOR
);
1366 // If config has explicitly requested DBO_TRX be either on or off by not
1367 // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
1368 // for things like blob stores (ExternalStore) which want auto-commit mode.
1373 * @param IDatabase $conn
1375 private function undoTransactionRoundFlags( IDatabase
$conn ) {
1376 if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
1377 return; // transaction rounds do not apply to these connections
1380 if ( $conn->getFlag( $conn::DBO_DEFAULT
) ) {
1381 $conn->restoreFlags( $conn::RESTORE_PRIOR
);
1385 public function flushReplicaSnapshots( $fname = __METHOD__
) {
1386 $this->forEachOpenReplicaConnection( function ( IDatabase
$conn ) {
1387 $conn->flushSnapshot( __METHOD__
);
1391 public function hasMasterConnection() {
1392 return $this->isOpen( $this->getWriterIndex() );
1395 public function hasMasterChanges() {
1397 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$pending ) {
1398 $pending |
= $conn->writesOrCallbacksPending();
1401 return (bool)$pending;
1404 public function lastMasterChangeTimestamp() {
1406 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$lastTime ) {
1407 $lastTime = max( $lastTime, $conn->lastDoneWrites() );
1413 public function hasOrMadeRecentMasterChanges( $age = null ) {
1414 $age = ( $age === null ) ?
$this->mWaitTimeout
: $age;
1416 return ( $this->hasMasterChanges()
1417 ||
$this->lastMasterChangeTimestamp() > microtime( true ) - $age );
1420 public function pendingMasterChangeCallers() {
1422 $this->forEachOpenMasterConnection( function ( IDatabase
$conn ) use ( &$fnames ) {
1423 $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
1429 public function getLaggedReplicaMode( $domain = false ) {
1430 // No-op if there is only one DB (also avoids recursion)
1431 if ( !$this->laggedReplicaMode
&& $this->getServerCount() > 1 ) {
1433 // See if laggedReplicaMode gets set
1434 $conn = $this->getConnection( self
::DB_REPLICA
, false, $domain );
1435 $this->reuseConnection( $conn );
1436 } catch ( DBConnectionError
$e ) {
1437 // Avoid expensive re-connect attempts and failures
1438 $this->allReplicasDownMode
= true;
1439 $this->laggedReplicaMode
= true;
1443 return $this->laggedReplicaMode
;
1447 * @param bool $domain
1449 * @deprecated 1.28; use getLaggedReplicaMode()
1451 public function getLaggedSlaveMode( $domain = false ) {
1452 return $this->getLaggedReplicaMode( $domain );
1455 public function laggedReplicaUsed() {
1456 return $this->laggedReplicaMode
;
1462 * @deprecated Since 1.28; use laggedReplicaUsed()
1464 public function laggedSlaveUsed() {
1465 return $this->laggedReplicaUsed();
1468 public function getReadOnlyReason( $domain = false, IDatabase
$conn = null ) {
1469 if ( $this->readOnlyReason
!== false ) {
1470 return $this->readOnlyReason
;
1471 } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
1472 if ( $this->allReplicasDownMode
) {
1473 return 'The database has been automatically locked ' .
1474 'until the replica database servers become available';
1476 return 'The database has been automatically locked ' .
1477 'while the replica database servers catch up to the master.';
1479 } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
1480 return 'The database master is running in read-only mode.';
1487 * @param string $domain Domain ID, or false for the current domain
1488 * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
1491 private function masterRunningReadOnly( $domain, IDatabase
$conn = null ) {
1492 $cache = $this->wanCache
;
1493 $masterServer = $this->getServerName( $this->getWriterIndex() );
1495 return (bool)$cache->getWithSetCallback(
1496 $cache->makeGlobalKey( __CLASS__
, 'server-read-only', $masterServer ),
1497 self
::TTL_CACHE_READONLY
,
1498 function () use ( $domain, $conn ) {
1499 $old = $this->trxProfiler
->setSilenced( true );
1501 $dbw = $conn ?
: $this->getConnection( self
::DB_MASTER
, [], $domain );
1502 $readOnly = (int)$dbw->serverIsReadOnly();
1504 $this->reuseConnection( $dbw );
1506 } catch ( DBError
$e ) {
1509 $this->trxProfiler
->setSilenced( $old );
1512 [ 'pcTTL' => $cache::TTL_PROC_LONG
, 'busyValue' => 0 ]
1516 public function allowLagged( $mode = null ) {
1517 if ( $mode === null ) {
1518 return $this->mAllowLagged
;
1520 $this->mAllowLagged
= $mode;
1522 return $this->mAllowLagged
;
1525 public function pingAll() {
1527 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$success ) {
1528 if ( !$conn->ping() ) {
1536 public function forEachOpenConnection( $callback, array $params = [] ) {
1537 foreach ( $this->mConns
as $connsByServer ) {
1538 foreach ( $connsByServer as $serverConns ) {
1539 foreach ( $serverConns as $conn ) {
1540 $mergedParams = array_merge( [ $conn ], $params );
1541 call_user_func_array( $callback, $mergedParams );
1547 public function forEachOpenMasterConnection( $callback, array $params = [] ) {
1548 $masterIndex = $this->getWriterIndex();
1549 foreach ( $this->mConns
as $connsByServer ) {
1550 if ( isset( $connsByServer[$masterIndex] ) ) {
1551 /** @var IDatabase $conn */
1552 foreach ( $connsByServer[$masterIndex] as $conn ) {
1553 $mergedParams = array_merge( [ $conn ], $params );
1554 call_user_func_array( $callback, $mergedParams );
1560 public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
1561 foreach ( $this->mConns
as $connsByServer ) {
1562 foreach ( $connsByServer as $i => $serverConns ) {
1563 if ( $i === $this->getWriterIndex() ) {
1564 continue; // skip master
1566 foreach ( $serverConns as $conn ) {
1567 $mergedParams = array_merge( [ $conn ], $params );
1568 call_user_func_array( $callback, $mergedParams );
1574 public function getMaxLag( $domain = false ) {
1579 if ( $this->getServerCount() <= 1 ) {
1580 return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
1583 $lagTimes = $this->getLagTimes( $domain );
1584 foreach ( $lagTimes as $i => $lag ) {
1585 if ( $this->mLoads
[$i] > 0 && $lag > $maxLag ) {
1587 $host = $this->mServers
[$i]['host'];
1592 return [ $host, $maxLag, $maxIndex ];
1595 public function getLagTimes( $domain = false ) {
1596 if ( $this->getServerCount() <= 1 ) {
1597 return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
1600 $knownLagTimes = []; // map of (server index => 0 seconds)
1601 $indexesWithLag = [];
1602 foreach ( $this->mServers
as $i => $server ) {
1603 if ( empty( $server['is static'] ) ) {
1604 $indexesWithLag[] = $i; // DB server might have replication lag
1606 $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
1610 return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) +
$knownLagTimes;
1613 public function safeGetLag( IDatabase
$conn ) {
1614 if ( $this->getServerCount() <= 1 ) {
1617 return $conn->getLag();
1622 * @param IDatabase $conn
1623 * @param DBMasterPos|bool $pos
1624 * @param int $timeout
1627 public function safeWaitForMasterPos( IDatabase
$conn, $pos = false, $timeout = 10 ) {
1628 if ( $this->getServerCount() <= 1 ||
!$conn->getLBInfo( 'replica' ) ) {
1629 return true; // server is not a replica DB
1633 // Get the current master position, opening a connection if needed
1634 $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
1635 if ( $masterConn ) {
1636 $pos = $masterConn->getMasterPos();
1638 $masterConn = $this->openConnection( $this->getWriterIndex(), self
::DOMAIN_ANY
);
1639 $pos = $masterConn->getMasterPos();
1640 $this->closeConnection( $masterConn );
1644 if ( $pos instanceof DBMasterPos
) {
1645 $result = $conn->masterPosWait( $pos, $timeout );
1646 if ( $result == -1 ||
is_null( $result ) ) {
1647 $msg = __METHOD__
. ': Timed out waiting on {host} pos {pos}';
1648 $this->replLogger
->warning( $msg,
1649 [ 'host' => $conn->getServer(), 'pos' => $pos ] );
1652 $this->replLogger
->info( __METHOD__
. ': Done' );
1656 $ok = false; // something is misconfigured
1657 $this->replLogger
->error( 'Could not get master pos for {host}',
1658 [ 'host' => $conn->getServer() ] );
1664 public function setTransactionListener( $name, callable
$callback = null ) {
1666 $this->trxRecurringCallbacks
[$name] = $callback;
1668 unset( $this->trxRecurringCallbacks
[$name] );
1670 $this->forEachOpenMasterConnection(
1671 function ( IDatabase
$conn ) use ( $name, $callback ) {
1672 $conn->setTransactionListener( $name, $callback );
1677 public function setTableAliases( array $aliases ) {
1678 $this->tableAliases
= $aliases;
1681 public function setDomainPrefix( $prefix ) {
1682 // Find connections to explicit foreign domains still marked as in-use...
1684 $this->forEachOpenConnection( function ( IDatabase
$conn ) use ( &$domainsInUse ) {
1685 // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
1686 // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
1687 if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
1688 $domainsInUse[] = $conn->getDomainID();
1692 // Do not switch connections to explicit foreign domains unless marked as safe
1693 if ( $domainsInUse ) {
1694 $domains = implode( ', ', $domainsInUse );
1695 throw new DBUnexpectedError( null,
1696 "Foreign domain connections are still in use ($domains)." );
1699 $oldDomain = $this->localDomain
->getId();
1700 $this->setLocalDomain( new DatabaseDomain(
1701 $this->localDomain
->getDatabase(),
1702 $this->localDomain
->getSchema(),
1706 $this->forEachOpenConnection( function ( IDatabase
$db ) use ( $prefix, $oldDomain ) {
1707 if ( !$db->getLBInfo( 'foreign' ) ) {
1708 $db->tablePrefix( $prefix );
1714 * @param DatabaseDomain $domain
1716 private function setLocalDomain( DatabaseDomain
$domain ) {
1717 $this->localDomain
= $domain;
1718 // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
1719 // always true, gracefully handle the case when they fail to account for escaping.
1720 if ( $this->localDomain
->getTablePrefix() != '' ) {
1721 $this->localDomainIdAlias
=
1722 $this->localDomain
->getDatabase() . '-' . $this->localDomain
->getTablePrefix();
1724 $this->localDomainIdAlias
= $this->localDomain
->getDatabase();
1729 * Make PHP ignore user aborts/disconnects until the returned
1730 * value leaves scope. This returns null and does nothing in CLI mode.
1732 * @return ScopedCallback|null
1734 final protected function getScopedPHPBehaviorForCommit() {
1735 if ( PHP_SAPI
!= 'cli' ) { // https://bugs.php.net/bug.php?id=47540
1736 $old = ignore_user_abort( true ); // avoid half-finished operations
1737 return new ScopedCallback( function () use ( $old ) {
1738 ignore_user_abort( $old );
1745 function __destruct() {
1746 // Avoid connection leaks for sanity
1751 class_alias( LoadBalancer
::class, 'LoadBalancer' );