3 * Database load balancing.
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
25 * Database load balancing object
31 private $mServers, $mConns, $mLoads, $mGroupLoads;
32 private $mErrorConnection;
33 private $mReadIndex, $mAllowLagged;
34 private $mWaitForPos, $mWaitTimeout;
35 private $mLaggedSlaveMode, $mLastError = 'Unknown error';
36 private $mParentInfo, $mLagTimes;
37 private $mLoadMonitorClass, $mLoadMonitor;
40 * @param array $params with keys:
41 * servers Required. Array of server info structures.
42 * masterWaitTimeout Replication lag wait timeout
43 * loadMonitor Name of a class used to fetch server lag and load.
46 function __construct( $params ) {
47 if ( !isset( $params['servers'] ) ) {
48 throw new MWException( __CLASS__
. ': missing servers parameter' );
50 $this->mServers
= $params['servers'];
52 if ( isset( $params['waitTimeout'] ) ) {
53 $this->mWaitTimeout
= $params['waitTimeout'];
55 $this->mWaitTimeout
= 10;
58 $this->mReadIndex
= -1;
59 $this->mWriteIndex
= -1;
60 $this->mConns
= array(
62 'foreignUsed' => array(),
63 'foreignFree' => array() );
64 $this->mLoads
= array();
65 $this->mWaitForPos
= false;
66 $this->mLaggedSlaveMode
= false;
67 $this->mErrorConnection
= false;
68 $this->mAllowLagged
= false;
70 if ( isset( $params['loadMonitor'] ) ) {
71 $this->mLoadMonitorClass
= $params['loadMonitor'];
73 $master = reset( $params['servers'] );
74 if ( isset( $master['type'] ) && $master['type'] === 'mysql' ) {
75 $this->mLoadMonitorClass
= 'LoadMonitor_MySQL';
77 $this->mLoadMonitorClass
= 'LoadMonitor_Null';
81 foreach ( $params['servers'] as $i => $server ) {
82 $this->mLoads
[$i] = $server['load'];
83 if ( isset( $server['groupLoads'] ) ) {
84 foreach ( $server['groupLoads'] as $group => $ratio ) {
85 if ( !isset( $this->mGroupLoads
[$group] ) ) {
86 $this->mGroupLoads
[$group] = array();
88 $this->mGroupLoads
[$group][$i] = $ratio;
95 * Get a LoadMonitor instance
99 function getLoadMonitor() {
100 if ( !isset( $this->mLoadMonitor
) ) {
101 $class = $this->mLoadMonitorClass
;
102 $this->mLoadMonitor
= new $class( $this );
104 return $this->mLoadMonitor
;
108 * Get or set arbitrary data used by the parent object, usually an LBFactory
112 function parentInfo( $x = null ) {
113 return wfSetVar( $this->mParentInfo
, $x );
117 * Given an array of non-normalised probabilities, this function will select
118 * an element and return the appropriate key
120 * @deprecated since 1.21, use ArrayUtils::pickRandom()
122 * @param $weights array
124 * @return bool|int|string
126 function pickRandom( $weights ) {
127 return ArrayUtils
::pickRandom( $weights );
131 * @param $loads array
133 * @return bool|int|string
135 function getRandomNonLagged( $loads, $wiki = false ) {
136 # Unset excessively lagged servers
137 $lags = $this->getLagTimes( $wiki );
138 foreach ( $lags as $i => $lag ) {
140 if ( $lag === false ) {
141 wfDebugLog( 'replication', "Server #$i is not replicating\n" );
143 } elseif ( isset( $this->mServers
[$i]['max lag'] ) && $lag > $this->mServers
[$i]['max lag'] ) {
144 wfDebugLog( 'replication', "Server #$i is excessively lagged ($lag seconds)\n" );
150 # Find out if all the slaves with non-zero load are lagged
152 foreach ( $loads as $load ) {
156 # No appropriate DB servers except maybe the master and some slaves with zero load
157 # Do NOT use the master
158 # Instead, this function will return false, triggering read-only mode,
159 # and a lagged slave will be used instead.
163 if ( count( $loads ) == 0 ) {
167 #wfDebugLog( 'connect', var_export( $loads, true ) );
169 # Return a random representative of the remainder
170 return ArrayUtils
::pickRandom( $loads );
174 * Get the index of the reader connection, which may be a slave
175 * This takes into account load ratios and lag times. It should
176 * always return a consistent index during a given invocation
178 * Side effect: opens connections to databases
181 * @throws MWException
182 * @return bool|int|string
184 function getReaderIndex( $group = false, $wiki = false ) {
185 global $wgReadOnly, $wgDBClusterTimeout, $wgDBAvgStatusPoll, $wgDBtype;
187 # @todo FIXME: For now, only go through all this for mysql databases
188 if ( $wgDBtype != 'mysql' ) {
189 return $this->getWriterIndex();
192 if ( count( $this->mServers
) == 1 ) {
193 # Skip the load balancing if there's only one server
195 } elseif ( $group === false and $this->mReadIndex
>= 0 ) {
196 # Shortcut if generic reader exists already
197 return $this->mReadIndex
;
200 wfProfileIn( __METHOD__
);
204 # convert from seconds to microseconds
205 $timeout = $wgDBClusterTimeout * 1e6
;
207 # Find the relevant load array
208 if ( $group !== false ) {
209 if ( isset( $this->mGroupLoads
[$group] ) ) {
210 $nonErrorLoads = $this->mGroupLoads
[$group];
212 # No loads for this group, return false and the caller can use some other group
213 wfDebug( __METHOD__
. ": no loads for group $group\n" );
214 wfProfileOut( __METHOD__
);
218 $nonErrorLoads = $this->mLoads
;
221 if ( !$nonErrorLoads ) {
222 wfProfileOut( __METHOD__
);
223 throw new MWException( "Empty server array given to LoadBalancer" );
226 # Scale the configured load ratios according to the dynamic load (if the load monitor supports it)
227 $this->getLoadMonitor()->scaleLoads( $nonErrorLoads, $group, $wiki );
229 $laggedSlaveMode = false;
231 # First try quickly looking through the available servers for a server that
234 $totalThreadsConnected = 0;
235 $overloadedServers = 0;
236 $currentLoads = $nonErrorLoads;
237 while ( count( $currentLoads ) ) {
238 if ( $wgReadOnly ||
$this->mAllowLagged ||
$laggedSlaveMode ) {
239 $i = ArrayUtils
::pickRandom( $currentLoads );
241 $i = $this->getRandomNonLagged( $currentLoads, $wiki );
242 if ( $i === false && count( $currentLoads ) != 0 ) {
243 # All slaves lagged. Switch to read-only mode
244 wfDebugLog( 'replication', "All slaves lagged. Switch to read-only mode\n" );
245 $wgReadOnly = 'The database has been automatically locked ' .
246 'while the slave database servers catch up to the master';
247 $i = ArrayUtils
::pickRandom( $currentLoads );
248 $laggedSlaveMode = true;
252 if ( $i === false ) {
253 # pickRandom() returned false
254 # This is permanent and means the configuration or the load monitor
255 # wants us to return false.
256 wfDebugLog( 'connect', __METHOD__
. ": pickRandom() returned false\n" );
257 wfProfileOut( __METHOD__
);
261 wfDebugLog( 'connect', __METHOD__
. ": Using reader #$i: {$this->mServers[$i]['host']}...\n" );
262 $conn = $this->openConnection( $i, $wiki );
265 wfDebugLog( 'connect', __METHOD__
. ": Failed connecting to $i/$wiki\n" );
266 unset( $nonErrorLoads[$i] );
267 unset( $currentLoads[$i] );
271 // Perform post-connection backoff
272 $threshold = isset( $this->mServers
[$i]['max threads'] )
273 ?
$this->mServers
[$i]['max threads'] : false;
274 $backoff = $this->getLoadMonitor()->postConnectionBackoff( $conn, $threshold );
276 // Decrement reference counter, we are finished with this connection.
277 // It will be incremented for the caller later.
278 if ( $wiki !== false ) {
279 $this->reuseConnection( $conn );
283 # Post-connection overload, don't use this server for now
284 $totalThreadsConnected +
= $backoff;
285 $overloadedServers++
;
286 unset( $currentLoads[$i] );
293 # No server found yet
296 # If all servers were down, quit now
297 if ( !count( $nonErrorLoads ) ) {
298 wfDebugLog( 'connect', "All servers down\n" );
302 # Some servers must have been overloaded
303 if ( $overloadedServers == 0 ) {
304 throw new MWException( __METHOD__
. ": unexpectedly found no overloaded servers" );
306 # Back off for a while
307 # Scale the sleep time by the number of connected threads, to produce a
308 # roughly constant global poll rate
309 $avgThreads = $totalThreadsConnected / $overloadedServers;
310 $totalElapsed +
= $this->sleep( $wgDBAvgStatusPoll * $avgThreads );
311 } while ( $totalElapsed < $timeout );
313 if ( $totalElapsed >= $timeout ) {
314 wfDebugLog( 'connect', "All servers busy\n" );
315 $this->mErrorConnection
= false;
316 $this->mLastError
= 'All servers busy';
319 if ( $i !== false ) {
320 # Slave connection successful
321 # Wait for the session master pos for a short time
322 if ( $this->mWaitForPos
&& $i > 0 ) {
323 if ( !$this->doWait( $i ) ) {
324 $this->mServers
[$i]['slave pos'] = $conn->getSlavePos();
327 if ( $this->mReadIndex
<= 0 && $this->mLoads
[$i] > 0 && $i !== false ) {
328 $this->mReadIndex
= $i;
331 wfProfileOut( __METHOD__
);
336 * Wait for a specified number of microseconds, and return the period waited
340 function sleep( $t ) {
341 wfProfileIn( __METHOD__
);
342 wfDebug( __METHOD__
. ": waiting $t us\n" );
344 wfProfileOut( __METHOD__
);
349 * Set the master wait position
350 * If a DB_SLAVE connection has been opened already, waits
351 * Otherwise sets a variable telling it to wait if such a connection is opened
352 * @param $pos DBMasterPos
354 public function waitFor( $pos ) {
355 wfProfileIn( __METHOD__
);
356 $this->mWaitForPos
= $pos;
357 $i = $this->mReadIndex
;
360 if ( !$this->doWait( $i ) ) {
361 $this->mServers
[$i]['slave pos'] = $this->getAnyOpenConnection( $i )->getSlavePos();
362 $this->mLaggedSlaveMode
= true;
365 wfProfileOut( __METHOD__
);
369 * Set the master wait position and wait for ALL slaves to catch up to it
370 * @param $pos DBMasterPos
372 public function waitForAll( $pos ) {
373 wfProfileIn( __METHOD__
);
374 $this->mWaitForPos
= $pos;
375 $serverCount = count( $this->mServers
);
376 for ( $i = 1; $i < $serverCount; $i++
) {
377 if ( $this->mLoads
[$i] > 0 ) {
378 $this->doWait( $i, true );
381 wfProfileOut( __METHOD__
);
385 * Get any open connection to a given server index, local or foreign
386 * Returns false if there is no connection open
389 * @return DatabaseBase|bool False on failure
391 function getAnyOpenConnection( $i ) {
392 foreach ( $this->mConns
as $conns ) {
393 if ( !empty( $conns[$i] ) ) {
394 return reset( $conns[$i] );
401 * Wait for a given slave to catch up to the master pos stored in $this
406 protected function doWait( $index, $open = false ) {
407 # Find a connection to wait on
408 $conn = $this->getAnyOpenConnection( $index );
411 wfDebug( __METHOD__
. ": no connection open\n" );
414 $conn = $this->openConnection( $index, '' );
416 wfDebug( __METHOD__
. ": failed to open connection\n" );
422 wfDebug( __METHOD__
. ": Waiting for slave #$index to catch up...\n" );
423 $result = $conn->masterPosWait( $this->mWaitForPos
, $this->mWaitTimeout
);
425 if ( $result == -1 ||
is_null( $result ) ) {
426 # Timed out waiting for slave, use master instead
427 wfDebug( __METHOD__
. ": Timed out waiting for slave #$index pos {$this->mWaitForPos}\n" );
430 wfDebug( __METHOD__
. ": Done\n" );
436 * Get a connection by index
437 * This is the main entry point for this class.
439 * @param $i Integer: server index
440 * @param array $groups query groups
441 * @param bool|string $wiki Wiki ID
443 * @throws MWException
444 * @return DatabaseBase
446 public function &getConnection( $i, $groups = array(), $wiki = false ) {
447 wfProfileIn( __METHOD__
);
449 if ( $i == DB_LAST
) {
450 wfProfileOut( __METHOD__
);
451 throw new MWException( 'Attempt to call ' . __METHOD__
. ' with deprecated server index DB_LAST' );
452 } elseif ( $i === null ||
$i === false ) {
453 wfProfileOut( __METHOD__
);
454 throw new MWException( 'Attempt to call ' . __METHOD__
. ' with invalid server index' );
457 if ( $wiki === wfWikiID() ) {
462 if ( $i == DB_MASTER
) {
463 $i = $this->getWriterIndex();
464 } elseif ( !is_array( $groups ) ) {
465 $groupIndex = $this->getReaderIndex( $groups, $wiki );
466 if ( $groupIndex !== false ) {
467 $serverName = $this->getServerName( $groupIndex );
468 wfDebug( __METHOD__
. ": using server $serverName for group $groups\n" );
472 foreach ( $groups as $group ) {
473 $groupIndex = $this->getReaderIndex( $group, $wiki );
474 if ( $groupIndex !== false ) {
475 $serverName = $this->getServerName( $groupIndex );
476 wfDebug( __METHOD__
. ": using server $serverName for group $group\n" );
483 # Operation-based index
484 if ( $i == DB_SLAVE
) {
485 $this->mLastError
= 'Unknown error'; // reset error string
486 $i = $this->getReaderIndex( false, $wiki );
487 # Couldn't find a working server in getReaderIndex()?
488 if ( $i === false ) {
489 $this->mLastError
= 'No working slave server: ' . $this->mLastError
;
490 wfProfileOut( __METHOD__
);
491 return $this->reportConnectionError();
495 # Now we have an explicit index into the servers array
496 $conn = $this->openConnection( $i, $wiki );
498 wfProfileOut( __METHOD__
);
499 return $this->reportConnectionError();
502 wfProfileOut( __METHOD__
);
507 * Mark a foreign connection as being available for reuse under a different
508 * DB name or prefix. This mechanism is reference-counted, and must be called
509 * the same number of times as getConnection() to work.
511 * @param DatabaseBase $conn
512 * @throws MWException
514 public function reuseConnection( $conn ) {
515 $serverIndex = $conn->getLBInfo( 'serverIndex' );
516 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
517 $dbName = $conn->getDBname();
518 $prefix = $conn->tablePrefix();
519 if ( strval( $prefix ) !== '' ) {
520 $wiki = "$dbName-$prefix";
524 if ( $serverIndex === null ||
$refCount === null ) {
525 wfDebug( __METHOD__
. ": this connection was not opened as a foreign connection\n" );
527 * This can happen in code like:
528 * foreach ( $dbs as $db ) {
529 * $conn = $lb->getConnection( DB_SLAVE, array(), $db );
531 * $lb->reuseConnection( $conn );
533 * When a connection to the local DB is opened in this way, reuseConnection()
538 if ( $this->mConns
['foreignUsed'][$serverIndex][$wiki] !== $conn ) {
539 throw new MWException( __METHOD__
. ": connection not found, has the connection been freed already?" );
541 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
542 if ( $refCount <= 0 ) {
543 $this->mConns
['foreignFree'][$serverIndex][$wiki] = $conn;
544 unset( $this->mConns
['foreignUsed'][$serverIndex][$wiki] );
545 wfDebug( __METHOD__
. ": freed connection $serverIndex/$wiki\n" );
547 wfDebug( __METHOD__
. ": reference count for $serverIndex/$wiki reduced to $refCount\n" );
552 * Get a database connection handle reference
554 * The handle's methods wrap simply wrap those of a DatabaseBase handle
556 * @see LoadBalancer::getConnection() for parameter information
559 * @param mixed $groups
560 * @param string $wiki
563 public function getConnectionRef( $db, $groups = array(), $wiki = false ) {
564 return new DBConnRef( $this, $this->getConnection( $db, $groups, $wiki ) );
568 * Get a database connection handle reference without connecting yet
570 * The handle's methods wrap simply wrap those of a DatabaseBase handle
572 * @see LoadBalancer::getConnection() for parameter information
575 * @param mixed $groups
576 * @param string $wiki
579 public function getLazyConnectionRef( $db, $groups = array(), $wiki = false ) {
580 return new DBConnRef( $this, array( $db, $groups, $wiki ) );
584 * Open a connection to the server given by the specified index
585 * Index must be an actual index into the array.
586 * If the server is already open, returns it.
588 * On error, returns false, and the connection which caused the
589 * error will be available via $this->mErrorConnection.
591 * @param $i Integer server index
592 * @param string $wiki wiki ID to open
593 * @return DatabaseBase
597 function openConnection( $i, $wiki = false ) {
598 wfProfileIn( __METHOD__
);
599 if ( $wiki !== false ) {
600 $conn = $this->openForeignConnection( $i, $wiki );
601 wfProfileOut( __METHOD__
);
604 if ( isset( $this->mConns
['local'][$i][0] ) ) {
605 $conn = $this->mConns
['local'][$i][0];
607 $server = $this->mServers
[$i];
608 $server['serverIndex'] = $i;
609 $conn = $this->reallyOpenConnection( $server, false );
610 if ( $conn->isOpen() ) {
611 wfDebug( "Connected to database $i at {$this->mServers[$i]['host']}\n" );
612 $this->mConns
['local'][$i][0] = $conn;
614 wfDebug( "Failed to connect to database $i at {$this->mServers[$i]['host']}\n" );
615 $this->mErrorConnection
= $conn;
619 wfProfileOut( __METHOD__
);
624 * Open a connection to a foreign DB, or return one if it is already open.
626 * Increments a reference count on the returned connection which locks the
627 * connection to the requested wiki. This reference count can be
628 * decremented by calling reuseConnection().
630 * If a connection is open to the appropriate server already, but with the wrong
631 * database, it will be switched to the right database and returned, as long as
632 * it has been freed first with reuseConnection().
634 * On error, returns false, and the connection which caused the
635 * error will be available via $this->mErrorConnection.
637 * @param $i Integer: server index
638 * @param string $wiki wiki ID to open
639 * @return DatabaseBase
641 function openForeignConnection( $i, $wiki ) {
642 wfProfileIn( __METHOD__
);
643 list( $dbName, $prefix ) = wfSplitWikiID( $wiki );
644 if ( isset( $this->mConns
['foreignUsed'][$i][$wiki] ) ) {
645 // Reuse an already-used connection
646 $conn = $this->mConns
['foreignUsed'][$i][$wiki];
647 wfDebug( __METHOD__
. ": reusing connection $i/$wiki\n" );
648 } elseif ( isset( $this->mConns
['foreignFree'][$i][$wiki] ) ) {
649 // Reuse a free connection for the same wiki
650 $conn = $this->mConns
['foreignFree'][$i][$wiki];
651 unset( $this->mConns
['foreignFree'][$i][$wiki] );
652 $this->mConns
['foreignUsed'][$i][$wiki] = $conn;
653 wfDebug( __METHOD__
. ": reusing free connection $i/$wiki\n" );
654 } elseif ( !empty( $this->mConns
['foreignFree'][$i] ) ) {
655 // Reuse a connection from another wiki
656 $conn = reset( $this->mConns
['foreignFree'][$i] );
657 $oldWiki = key( $this->mConns
['foreignFree'][$i] );
659 if ( !$conn->selectDB( $dbName ) ) {
660 $this->mLastError
= "Error selecting database $dbName on server " .
661 $conn->getServer() . " from client host " . wfHostname() . "\n";
662 $this->mErrorConnection
= $conn;
665 $conn->tablePrefix( $prefix );
666 unset( $this->mConns
['foreignFree'][$i][$oldWiki] );
667 $this->mConns
['foreignUsed'][$i][$wiki] = $conn;
668 wfDebug( __METHOD__
. ": reusing free connection from $oldWiki for $wiki\n" );
671 // Open a new connection
672 $server = $this->mServers
[$i];
673 $server['serverIndex'] = $i;
674 $server['foreignPoolRefCount'] = 0;
675 $server['foreign'] = true;
676 $conn = $this->reallyOpenConnection( $server, $dbName );
677 if ( !$conn->isOpen() ) {
678 wfDebug( __METHOD__
. ": error opening connection for $i/$wiki\n" );
679 $this->mErrorConnection
= $conn;
682 $conn->tablePrefix( $prefix );
683 $this->mConns
['foreignUsed'][$i][$wiki] = $conn;
684 wfDebug( __METHOD__
. ": opened new connection for $i/$wiki\n" );
688 // Increment reference count
690 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
691 $conn->setLBInfo( 'foreignPoolRefCount', $refCount +
1 );
693 wfProfileOut( __METHOD__
);
698 * Test if the specified index represents an open connection
700 * @param $index Integer: server index
704 function isOpen( $index ) {
705 if ( !is_integer( $index ) ) {
708 return (bool)$this->getAnyOpenConnection( $index );
712 * Really opens a connection. Uncached.
713 * Returns a Database object whether or not the connection was successful.
717 * @param $dbNameOverride bool
718 * @throws MWException
719 * @return DatabaseBase
721 function reallyOpenConnection( $server, $dbNameOverride = false ) {
722 if ( !is_array( $server ) ) {
723 throw new MWException( 'You must update your load-balancing configuration. ' .
724 'See DefaultSettings.php entry for $wgDBservers.' );
727 if ( $dbNameOverride !== false ) {
728 $server['dbname'] = $dbNameOverride;
733 $db = DatabaseBase
::factory( $server['type'], $server );
734 } catch ( DBConnectionError
$e ) {
735 // FIXME: This is probably the ugliest thing I have ever done to
736 // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
740 $db->setLBInfo( $server );
741 if ( isset( $server['fakeSlaveLag'] ) ) {
742 $db->setFakeSlaveLag( $server['fakeSlaveLag'] );
744 if ( isset( $server['fakeMaster'] ) ) {
745 $db->setFakeMaster( true );
751 * @throws DBConnectionError
754 private function reportConnectionError() {
755 $conn = $this->mErrorConnection
; // The connection which caused the error
757 if ( !is_object( $conn ) ) {
758 // No last connection, probably due to all servers being too busy
759 wfLogDBError( "LB failure with no last connection. Connection error: {$this->mLastError}\n" );
761 // If all servers were busy, mLastError will contain something sensible
762 throw new DBConnectionError( null, $this->mLastError
);
764 $server = $conn->getProperty( 'mServer' );
765 wfLogDBError( "Connection error: {$this->mLastError} ({$server})\n" );
766 $conn->reportConnectionError( "{$this->mLastError} ({$server})" ); // throws DBConnectionError
768 return false; /* not reached */
774 function getWriterIndex() {
779 * Returns true if the specified index is a valid server index
784 function haveIndex( $i ) {
785 return array_key_exists( $i, $this->mServers
);
789 * Returns true if the specified index is valid and has non-zero load
794 function isNonZeroLoad( $i ) {
795 return array_key_exists( $i, $this->mServers
) && $this->mLoads
[$i] != 0;
799 * Get the number of defined servers (not the number of open connections)
803 function getServerCount() {
804 return count( $this->mServers
);
808 * Get the host name or IP address of the server with the specified index
809 * Prefer a readable name if available.
813 function getServerName( $i ) {
814 if ( isset( $this->mServers
[$i]['hostName'] ) ) {
815 return $this->mServers
[$i]['hostName'];
816 } elseif ( isset( $this->mServers
[$i]['host'] ) ) {
817 return $this->mServers
[$i]['host'];
824 * Return the server info structure for a given index, or false if the index is invalid.
828 function getServerInfo( $i ) {
829 if ( isset( $this->mServers
[$i] ) ) {
830 return $this->mServers
[$i];
837 * Sets the server info structure for the given index. Entry at index $i is created if it doesn't exist
841 function setServerInfo( $i, $serverInfo ) {
842 $this->mServers
[$i] = $serverInfo;
846 * Get the current master position for chronology control purposes
849 function getMasterPos() {
850 # If this entire request was served from a slave without opening a connection to the
851 # master (however unlikely that may be), then we can fetch the position from the slave.
852 $masterConn = $this->getAnyOpenConnection( 0 );
853 if ( !$masterConn ) {
854 $serverCount = count( $this->mServers
);
855 for ( $i = 1; $i < $serverCount; $i++
) {
856 $conn = $this->getAnyOpenConnection( $i );
858 wfDebug( "Master pos fetched from slave\n" );
859 return $conn->getSlavePos();
863 wfDebug( "Master pos fetched from master\n" );
864 return $masterConn->getMasterPos();
870 * Close all open connections
872 function closeAll() {
873 foreach ( $this->mConns
as $conns2 ) {
874 foreach ( $conns2 as $conns3 ) {
875 foreach ( $conns3 as $conn ) {
880 $this->mConns
= array(
882 'foreignFree' => array(),
883 'foreignUsed' => array(),
888 * Deprecated function, typo in function name
890 * @deprecated in 1.18
893 function closeConnecton( $conn ) {
894 wfDeprecated( __METHOD__
, '1.18' );
895 $this->closeConnection( $conn );
900 * Using this function makes sure the LoadBalancer knows the connection is closed.
901 * If you use $conn->close() directly, the load balancer won't update its state.
902 * @param $conn DatabaseBase
904 function closeConnection( $conn ) {
906 foreach ( $this->mConns
as $i1 => $conns2 ) {
907 foreach ( $conns2 as $i2 => $conns3 ) {
908 foreach ( $conns3 as $i3 => $candidateConn ) {
909 if ( $conn === $candidateConn ) {
911 unset( $this->mConns
[$i1][$i2][$i3] );
924 * Commit transactions on all open connections
926 function commitAll() {
927 foreach ( $this->mConns
as $conns2 ) {
928 foreach ( $conns2 as $conns3 ) {
929 foreach ( $conns3 as $conn ) {
930 if ( $conn->trxLevel() ) {
931 $conn->commit( __METHOD__
, 'flush' );
939 * Issue COMMIT only on master, only if queries were done on connection
941 function commitMasterChanges() {
942 // Always 0, but who knows.. :)
943 $masterIndex = $this->getWriterIndex();
944 foreach ( $this->mConns
as $conns2 ) {
945 if ( empty( $conns2[$masterIndex] ) ) {
948 foreach ( $conns2[$masterIndex] as $conn ) {
949 if ( $conn->trxLevel() && $conn->writesOrCallbacksPending() ) {
950 $conn->commit( __METHOD__
, 'flush' );
960 function waitTimeout( $value = null ) {
961 return wfSetVar( $this->mWaitTimeout
, $value );
967 function getLaggedSlaveMode() {
968 return $this->mLaggedSlaveMode
;
972 * Disables/enables lag checks
976 function allowLagged( $mode = null ) {
977 if ( $mode === null ) {
978 return $this->mAllowLagged
;
980 $this->mAllowLagged
= $mode;
981 return $this->mAllowLagged
;
989 foreach ( $this->mConns
as $conns2 ) {
990 foreach ( $conns2 as $conns3 ) {
991 foreach ( $conns3 as $conn ) {
992 if ( !$conn->ping() ) {
1002 * Call a function with each open connection object
1004 * @param array $params
1006 function forEachOpenConnection( $callback, $params = array() ) {
1007 foreach ( $this->mConns
as $conns2 ) {
1008 foreach ( $conns2 as $conns3 ) {
1009 foreach ( $conns3 as $conn ) {
1010 $mergedParams = array_merge( array( $conn ), $params );
1011 call_user_func_array( $callback, $mergedParams );
1018 * Get the hostname and lag time of the most-lagged slave.
1019 * This is useful for maintenance scripts that need to throttle their updates.
1020 * May attempt to open connections to slaves on the default DB. If there is
1021 * no lag, the maximum lag will be reported as -1.
1023 * @param string $wiki Wiki ID, or false for the default database
1025 * @return array ( host, max lag, index of max lagged host )
1027 function getMaxLag( $wiki = false ) {
1031 if ( $this->getServerCount() > 1 ) { // no replication = no lag
1032 foreach ( $this->mServers
as $i => $conn ) {
1034 if ( $wiki === false ) {
1035 $conn = $this->getAnyOpenConnection( $i );
1038 $conn = $this->openConnection( $i, $wiki );
1043 $lag = $conn->getLag();
1044 if ( $lag > $maxLag ) {
1046 $host = $this->mServers
[$i]['host'];
1051 return array( $host, $maxLag, $maxIndex );
1055 * Get lag time for each server
1056 * Results are cached for a short time in memcached, and indefinitely in the process cache
1062 function getLagTimes( $wiki = false ) {
1064 if ( isset( $this->mLagTimes
) ) {
1065 return $this->mLagTimes
;
1067 if ( $this->getServerCount() == 1 ) {
1069 $this->mLagTimes
= array( 0 => 0 );
1071 # Send the request to the load monitor
1072 $this->mLagTimes
= $this->getLoadMonitor()->getLagTimes(
1073 array_keys( $this->mServers
), $wiki );
1075 return $this->mLagTimes
;
1079 * Get the lag in seconds for a given connection, or zero if this load
1080 * balancer does not have replication enabled.
1082 * This should be used in preference to Database::getLag() in cases where
1083 * replication may not be in use, since there is no way to determine if
1084 * replication is in use at the connection level without running
1085 * potentially restricted queries such as SHOW SLAVE STATUS. Using this
1086 * function instead of Database::getLag() avoids a fatal error in this
1087 * case on many installations.
1089 * @param $conn DatabaseBase
1093 function safeGetLag( $conn ) {
1094 if ( $this->getServerCount() == 1 ) {
1097 return $conn->getLag();
1102 * Clear the cache for getLagTimes
1104 function clearLagTimeCache() {
1105 $this->mLagTimes
= null;
1110 * Helper class to handle automatically marking connectons as reusable (via RAII pattern)
1111 * as well handling deferring the actual network connection until the handle is used
1116 class DBConnRef
implements IDatabase
{
1117 /** @var LoadBalancer */
1119 /** @var DatabaseBase|null */
1121 /** @var Array|null */
1125 * @param $lb LoadBalancer
1126 * @param $conn DatabaseBase|array Connection or (server index, group, wiki ID) array
1128 public function __construct( LoadBalancer
$lb, $conn ) {
1130 if ( $conn instanceof DatabaseBase
) {
1131 $this->conn
= $conn;
1133 $this->params
= $conn;
1137 public function __call( $name, $arguments ) {
1138 if ( $this->conn
=== null ) {
1139 list( $db, $groups, $wiki ) = $this->params
;
1140 $this->conn
= $this->lb
->getConnection( $db, $groups, $wiki );
1142 return call_user_func_array( array( $this->conn
, $name ), $arguments );
1145 function __destruct() {
1146 if ( $this->conn
!== null ) {
1147 $this->lb
->reuseConnection( $this->conn
);