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[lhc/web/wiklou.git] / includes / db / LoadBalancer.php
1 <?php
2 /**
3 * Database load balancing.
4 *
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.
9 *
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.
14 *
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
19 *
20 * @file
21 * @ingroup Database
22 */
23
24 /**
25 * Database load balancing object
26 *
27 * @todo document
28 * @ingroup Database
29 */
30 class LoadBalancer {
31 /** @var array Map of (server index => server config array) */
32 private $mServers;
33 /** @var array Map of (local/foreignUsed/foreignFree => server index => DatabaseBase array) */
34 private $mConns;
35 /** @var array Map of (server index => weight) */
36 private $mLoads;
37 /** @var array Map of (group => server index => weight) */
38 private $mGroupLoads;
39 /** @var bool Whether to disregard slave lag as a factor in slave selection */
40 private $mAllowLagged;
41 /** @var integer Seconds to spend waiting on slave lag to resolve */
42 private $mWaitTimeout;
43
44 /** @var array LBFactory information */
45 private $mParentInfo;
46 /** @var string The LoadMonitor subclass name */
47 private $mLoadMonitorClass;
48 /** @var LoadMonitor */
49 private $mLoadMonitor;
50
51 /** @var bool|DatabaseBase Database connection that caused a problem */
52 private $mErrorConnection;
53 /** @var integer The generic (not query grouped) slave index (of $mServers) */
54 private $mReadIndex;
55 /** @var bool|DBMasterPos False if not set */
56 private $mWaitForPos;
57 /** @var bool Whether the generic reader fell back to a lagged slave */
58 private $mLaggedSlaveMode;
59 /** @var string The last DB selection or connection error */
60 private $mLastError = 'Unknown error';
61 /** @var ProcessCacheLRU */
62 private $mProcCache;
63
64 /**
65 * @param array $params Array with keys:
66 * servers Required. Array of server info structures.
67 * loadMonitor Name of a class used to fetch server lag and load.
68 * @throws MWException
69 */
70 function __construct( $params ) {
71 if ( !isset( $params['servers'] ) ) {
72 throw new MWException( __CLASS__ . ': missing servers parameter' );
73 }
74 $this->mServers = $params['servers'];
75 $this->mWaitTimeout = 10;
76
77 $this->mReadIndex = -1;
78 $this->mWriteIndex = -1;
79 $this->mConns = array(
80 'local' => array(),
81 'foreignUsed' => array(),
82 'foreignFree' => array() );
83 $this->mLoads = array();
84 $this->mWaitForPos = false;
85 $this->mLaggedSlaveMode = false;
86 $this->mErrorConnection = false;
87 $this->mAllowLagged = false;
88
89 if ( isset( $params['loadMonitor'] ) ) {
90 $this->mLoadMonitorClass = $params['loadMonitor'];
91 } else {
92 $master = reset( $params['servers'] );
93 if ( isset( $master['type'] ) && $master['type'] === 'mysql' ) {
94 $this->mLoadMonitorClass = 'LoadMonitorMySQL';
95 } else {
96 $this->mLoadMonitorClass = 'LoadMonitorNull';
97 }
98 }
99
100 foreach ( $params['servers'] as $i => $server ) {
101 $this->mLoads[$i] = $server['load'];
102 if ( isset( $server['groupLoads'] ) ) {
103 foreach ( $server['groupLoads'] as $group => $ratio ) {
104 if ( !isset( $this->mGroupLoads[$group] ) ) {
105 $this->mGroupLoads[$group] = array();
106 }
107 $this->mGroupLoads[$group][$i] = $ratio;
108 }
109 }
110 }
111
112 $this->mProcCache = new ProcessCacheLRU( 30 );
113 }
114
115 /**
116 * Get a LoadMonitor instance
117 *
118 * @return LoadMonitor
119 */
120 function getLoadMonitor() {
121 if ( !isset( $this->mLoadMonitor ) ) {
122 $class = $this->mLoadMonitorClass;
123 $this->mLoadMonitor = new $class( $this );
124 }
125
126 return $this->mLoadMonitor;
127 }
128
129 /**
130 * Get or set arbitrary data used by the parent object, usually an LBFactory
131 * @param mixed $x
132 * @return mixed
133 */
134 function parentInfo( $x = null ) {
135 return wfSetVar( $this->mParentInfo, $x );
136 }
137
138 /**
139 * Given an array of non-normalised probabilities, this function will select
140 * an element and return the appropriate key
141 *
142 * @deprecated since 1.21, use ArrayUtils::pickRandom()
143 *
144 * @param array $weights
145 * @return bool|int|string
146 */
147 function pickRandom( $weights ) {
148 return ArrayUtils::pickRandom( $weights );
149 }
150
151 /**
152 * @param array $loads
153 * @param bool|string $wiki Wiki to get non-lagged for
154 * @return bool|int|string
155 */
156 function getRandomNonLagged( $loads, $wiki = false ) {
157 # Unset excessively lagged servers
158 $lags = $this->getLagTimes( $wiki );
159 foreach ( $lags as $i => $lag ) {
160 if ( $i != 0 ) {
161 if ( $lag === false ) {
162 wfDebugLog( 'replication', "Server #$i is not replicating" );
163 unset( $loads[$i] );
164 } elseif ( isset( $this->mServers[$i]['max lag'] ) && $lag > $this->mServers[$i]['max lag'] ) {
165 wfDebugLog( 'replication', "Server #$i is excessively lagged ($lag seconds)" );
166 unset( $loads[$i] );
167 }
168 }
169 }
170
171 # Find out if all the slaves with non-zero load are lagged
172 $sum = 0;
173 foreach ( $loads as $load ) {
174 $sum += $load;
175 }
176 if ( $sum == 0 ) {
177 # No appropriate DB servers except maybe the master and some slaves with zero load
178 # Do NOT use the master
179 # Instead, this function will return false, triggering read-only mode,
180 # and a lagged slave will be used instead.
181 return false;
182 }
183
184 if ( count( $loads ) == 0 ) {
185 return false;
186 }
187
188 #wfDebugLog( 'connect', var_export( $loads, true ) );
189
190 # Return a random representative of the remainder
191 return ArrayUtils::pickRandom( $loads );
192 }
193
194 /**
195 * Get the index of the reader connection, which may be a slave
196 * This takes into account load ratios and lag times. It should
197 * always return a consistent index during a given invocation
198 *
199 * Side effect: opens connections to databases
200 * @param bool|string $group
201 * @param bool|string $wiki
202 * @throws MWException
203 * @return bool|int|string
204 */
205 function getReaderIndex( $group = false, $wiki = false ) {
206 global $wgReadOnly, $wgDBtype;
207
208 # @todo FIXME: For now, only go through all this for mysql databases
209 if ( $wgDBtype != 'mysql' ) {
210 return $this->getWriterIndex();
211 }
212
213 if ( count( $this->mServers ) == 1 ) {
214 # Skip the load balancing if there's only one server
215 return 0;
216 } elseif ( $group === false && $this->mReadIndex >= 0 ) {
217 # Shortcut if generic reader exists already
218 return $this->mReadIndex;
219 }
220
221 $section = new ProfileSection( __METHOD__ );
222
223 # Find the relevant load array
224 if ( $group !== false ) {
225 if ( isset( $this->mGroupLoads[$group] ) ) {
226 $nonErrorLoads = $this->mGroupLoads[$group];
227 } else {
228 # No loads for this group, return false and the caller can use some other group
229 wfDebug( __METHOD__ . ": no loads for group $group\n" );
230
231 return false;
232 }
233 } else {
234 $nonErrorLoads = $this->mLoads;
235 }
236
237 if ( !count( $nonErrorLoads ) ) {
238 throw new MWException( "Empty server array given to LoadBalancer" );
239 }
240
241 # Scale the configured load ratios according to the dynamic load (if the load monitor supports it)
242 $this->getLoadMonitor()->scaleLoads( $nonErrorLoads, $group, $wiki );
243
244 $laggedSlaveMode = false;
245
246 # No server found yet
247 $i = false;
248 # First try quickly looking through the available servers for a server that
249 # meets our criteria
250 $currentLoads = $nonErrorLoads;
251 while ( count( $currentLoads ) ) {
252 if ( $wgReadOnly || $this->mAllowLagged || $laggedSlaveMode ) {
253 $i = ArrayUtils::pickRandom( $currentLoads );
254 } else {
255 $i = $this->getRandomNonLagged( $currentLoads, $wiki );
256 if ( $i === false && count( $currentLoads ) != 0 ) {
257 # All slaves lagged. Switch to read-only mode
258 wfDebugLog( 'replication', "All slaves lagged. Switch to read-only mode" );
259 $wgReadOnly = 'The database has been automatically locked ' .
260 'while the slave database servers catch up to the master';
261 $i = ArrayUtils::pickRandom( $currentLoads );
262 $laggedSlaveMode = true;
263 }
264 }
265
266 if ( $i === false ) {
267 # pickRandom() returned false
268 # This is permanent and means the configuration or the load monitor
269 # wants us to return false.
270 wfDebugLog( 'connect', __METHOD__ . ": pickRandom() returned false" );
271
272 return false;
273 }
274
275 wfDebugLog( 'connect', __METHOD__ .
276 ": Using reader #$i: {$this->mServers[$i]['host']}..." );
277
278 $conn = $this->openConnection( $i, $wiki );
279 if ( !$conn ) {
280 wfDebugLog( 'connect', __METHOD__ . ": Failed connecting to $i/$wiki" );
281 unset( $nonErrorLoads[$i] );
282 unset( $currentLoads[$i] );
283 $i = false;
284 continue;
285 }
286
287 // Decrement reference counter, we are finished with this connection.
288 // It will be incremented for the caller later.
289 if ( $wiki !== false ) {
290 $this->reuseConnection( $conn );
291 }
292
293 # Return this server
294 break;
295 }
296
297 # If all servers were down, quit now
298 if ( !count( $nonErrorLoads ) ) {
299 wfDebugLog( 'connect', "All servers down" );
300 }
301
302 if ( $i !== false ) {
303 # Slave connection successful
304 # Wait for the session master pos for a short time
305 if ( $this->mWaitForPos && $i > 0 ) {
306 if ( !$this->doWait( $i ) ) {
307 $this->mServers[$i]['slave pos'] = $conn->getSlavePos();
308 }
309 }
310 if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group !== false ) {
311 $this->mReadIndex = $i;
312 }
313 }
314
315 return $i;
316 }
317
318 /**
319 * Set the master wait position
320 * If a DB_SLAVE connection has been opened already, waits
321 * Otherwise sets a variable telling it to wait if such a connection is opened
322 * @param DBMasterPos $pos
323 */
324 public function waitFor( $pos ) {
325 wfProfileIn( __METHOD__ );
326 $this->mWaitForPos = $pos;
327 $i = $this->mReadIndex;
328
329 if ( $i > 0 ) {
330 if ( !$this->doWait( $i ) ) {
331 $this->mServers[$i]['slave pos'] = $this->getAnyOpenConnection( $i )->getSlavePos();
332 $this->mLaggedSlaveMode = true;
333 }
334 }
335 wfProfileOut( __METHOD__ );
336 }
337
338 /**
339 * Set the master wait position and wait for ALL slaves to catch up to it
340 * @param DBMasterPos $pos
341 * @param int $timeout Max seconds to wait; default is mWaitTimeout
342 * @return bool Success (able to connect and no timeouts reached)
343 */
344 public function waitForAll( $pos, $timeout = null ) {
345 wfProfileIn( __METHOD__ );
346 $this->mWaitForPos = $pos;
347 $serverCount = count( $this->mServers );
348
349 $ok = true;
350 for ( $i = 1; $i < $serverCount; $i++ ) {
351 if ( $this->mLoads[$i] > 0 ) {
352 $ok = $this->doWait( $i, true, $timeout ) && $ok;
353 }
354 }
355 wfProfileOut( __METHOD__ );
356
357 return $ok;
358 }
359
360 /**
361 * Get any open connection to a given server index, local or foreign
362 * Returns false if there is no connection open
363 *
364 * @param int $i
365 * @return DatabaseBase|bool False on failure
366 */
367 function getAnyOpenConnection( $i ) {
368 foreach ( $this->mConns as $conns ) {
369 if ( !empty( $conns[$i] ) ) {
370 return reset( $conns[$i] );
371 }
372 }
373
374 return false;
375 }
376
377 /**
378 * Wait for a given slave to catch up to the master pos stored in $this
379 * @param int $index Server index
380 * @param bool $open Check the server even if a new connection has to be made
381 * @param int $timeout Max seconds to wait; default is mWaitTimeout
382 * @return bool
383 */
384 protected function doWait( $index, $open = false, $timeout = null ) {
385 $close = false; // close the connection afterwards
386
387 # Find a connection to wait on, creating one if needed and allowed
388 $conn = $this->getAnyOpenConnection( $index );
389 if ( !$conn ) {
390 if ( !$open ) {
391 wfDebug( __METHOD__ . ": no connection open\n" );
392
393 return false;
394 } else {
395 $conn = $this->openConnection( $index, '' );
396 if ( !$conn ) {
397 wfDebug( __METHOD__ . ": failed to open connection\n" );
398
399 return false;
400 }
401 // Avoid connection spam in waitForAll() when connections
402 // are made just for the sake of doing this lag check.
403 $close = true;
404 }
405 }
406
407 wfDebug( __METHOD__ . ": Waiting for slave #$index to catch up...\n" );
408 $timeout = $timeout ?: $this->mWaitTimeout;
409 $result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
410
411 if ( $result == -1 || is_null( $result ) ) {
412 # Timed out waiting for slave, use master instead
413 wfDebug( __METHOD__ . ": Timed out waiting for slave #$index pos {$this->mWaitForPos}\n" );
414 $ok = false;
415 } else {
416 wfDebug( __METHOD__ . ": Done\n" );
417 $ok = true;
418 }
419
420 if ( $close ) {
421 $this->closeConnection( $conn );
422 }
423
424 return $ok;
425 }
426
427 /**
428 * Get a connection by index
429 * This is the main entry point for this class.
430 *
431 * @param int $i Server index
432 * @param array $groups Query groups
433 * @param bool|string $wiki Wiki ID
434 *
435 * @throws MWException
436 * @return DatabaseBase
437 */
438 public function &getConnection( $i, $groups = array(), $wiki = false ) {
439 wfProfileIn( __METHOD__ );
440
441 if ( $i === null || $i === false ) {
442 wfProfileOut( __METHOD__ );
443 throw new MWException( 'Attempt to call ' . __METHOD__ .
444 ' with invalid server index' );
445 }
446
447 if ( $wiki === wfWikiID() ) {
448 $wiki = false;
449 }
450
451 # Query groups
452 if ( $i == DB_MASTER ) {
453 $i = $this->getWriterIndex();
454 } elseif ( !is_array( $groups ) ) {
455 $groupIndex = $this->getReaderIndex( $groups, $wiki );
456 if ( $groupIndex !== false ) {
457 $serverName = $this->getServerName( $groupIndex );
458 wfDebug( __METHOD__ . ": using server $serverName for group $groups\n" );
459 $i = $groupIndex;
460 }
461 } else {
462 foreach ( $groups as $group ) {
463 $groupIndex = $this->getReaderIndex( $group, $wiki );
464 if ( $groupIndex !== false ) {
465 $serverName = $this->getServerName( $groupIndex );
466 wfDebug( __METHOD__ . ": using server $serverName for group $group\n" );
467 $i = $groupIndex;
468 break;
469 }
470 }
471 }
472
473 # Operation-based index
474 if ( $i == DB_SLAVE ) {
475 $this->mLastError = 'Unknown error'; // reset error string
476 $i = $this->getReaderIndex( false, $wiki );
477 # Couldn't find a working server in getReaderIndex()?
478 if ( $i === false ) {
479 $this->mLastError = 'No working slave server: ' . $this->mLastError;
480 wfProfileOut( __METHOD__ );
481
482 return $this->reportConnectionError();
483 }
484 }
485
486 # Now we have an explicit index into the servers array
487 $conn = $this->openConnection( $i, $wiki );
488 if ( !$conn ) {
489 wfProfileOut( __METHOD__ );
490
491 return $this->reportConnectionError();
492 }
493
494 wfProfileOut( __METHOD__ );
495
496 return $conn;
497 }
498
499 /**
500 * Mark a foreign connection as being available for reuse under a different
501 * DB name or prefix. This mechanism is reference-counted, and must be called
502 * the same number of times as getConnection() to work.
503 *
504 * @param DatabaseBase $conn
505 * @throws MWException
506 */
507 public function reuseConnection( $conn ) {
508 $serverIndex = $conn->getLBInfo( 'serverIndex' );
509 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
510 if ( $serverIndex === null || $refCount === null ) {
511 wfDebug( __METHOD__ . ": this connection was not opened as a foreign connection\n" );
512
513 /**
514 * This can happen in code like:
515 * foreach ( $dbs as $db ) {
516 * $conn = $lb->getConnection( DB_SLAVE, array(), $db );
517 * ...
518 * $lb->reuseConnection( $conn );
519 * }
520 * When a connection to the local DB is opened in this way, reuseConnection()
521 * should be ignored
522 */
523
524 return;
525 }
526
527 $dbName = $conn->getDBname();
528 $prefix = $conn->tablePrefix();
529 if ( strval( $prefix ) !== '' ) {
530 $wiki = "$dbName-$prefix";
531 } else {
532 $wiki = $dbName;
533 }
534 if ( $this->mConns['foreignUsed'][$serverIndex][$wiki] !== $conn ) {
535 throw new MWException( __METHOD__ . ": connection not found, has " .
536 "the connection been freed already?" );
537 }
538 $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
539 if ( $refCount <= 0 ) {
540 $this->mConns['foreignFree'][$serverIndex][$wiki] = $conn;
541 unset( $this->mConns['foreignUsed'][$serverIndex][$wiki] );
542 wfDebug( __METHOD__ . ": freed connection $serverIndex/$wiki\n" );
543 } else {
544 wfDebug( __METHOD__ . ": reference count for $serverIndex/$wiki reduced to $refCount\n" );
545 }
546 }
547
548 /**
549 * Get a database connection handle reference
550 *
551 * The handle's methods wrap simply wrap those of a DatabaseBase handle
552 *
553 * @see LoadBalancer::getConnection() for parameter information
554 *
555 * @param int $db
556 * @param mixed $groups
557 * @param bool|string $wiki
558 * @return DBConnRef
559 */
560 public function getConnectionRef( $db, $groups = array(), $wiki = false ) {
561 return new DBConnRef( $this, $this->getConnection( $db, $groups, $wiki ) );
562 }
563
564 /**
565 * Get a database connection handle reference without connecting yet
566 *
567 * The handle's methods wrap simply wrap those of a DatabaseBase handle
568 *
569 * @see LoadBalancer::getConnection() for parameter information
570 *
571 * @param int $db
572 * @param mixed $groups
573 * @param bool|string $wiki
574 * @return DBConnRef
575 */
576 public function getLazyConnectionRef( $db, $groups = array(), $wiki = false ) {
577 return new DBConnRef( $this, array( $db, $groups, $wiki ) );
578 }
579
580 /**
581 * Open a connection to the server given by the specified index
582 * Index must be an actual index into the array.
583 * If the server is already open, returns it.
584 *
585 * On error, returns false, and the connection which caused the
586 * error will be available via $this->mErrorConnection.
587 *
588 * @param int $i Server index
589 * @param bool|string $wiki Wiki ID to open
590 * @return DatabaseBase
591 *
592 * @access private
593 */
594 function openConnection( $i, $wiki = false ) {
595 wfProfileIn( __METHOD__ );
596 if ( $wiki !== false ) {
597 $conn = $this->openForeignConnection( $i, $wiki );
598 wfProfileOut( __METHOD__ );
599
600 return $conn;
601 }
602 if ( isset( $this->mConns['local'][$i][0] ) ) {
603 $conn = $this->mConns['local'][$i][0];
604 } else {
605 $server = $this->mServers[$i];
606 $server['serverIndex'] = $i;
607 $conn = $this->reallyOpenConnection( $server, false );
608 if ( $conn->isOpen() ) {
609 wfDebug( "Connected to database $i at {$this->mServers[$i]['host']}\n" );
610 $this->mConns['local'][$i][0] = $conn;
611 } else {
612 wfDebug( "Failed to connect to database $i at {$this->mServers[$i]['host']}\n" );
613 $this->mErrorConnection = $conn;
614 $conn = false;
615 }
616 }
617 wfProfileOut( __METHOD__ );
618
619 return $conn;
620 }
621
622 /**
623 * Open a connection to a foreign DB, or return one if it is already open.
624 *
625 * Increments a reference count on the returned connection which locks the
626 * connection to the requested wiki. This reference count can be
627 * decremented by calling reuseConnection().
628 *
629 * If a connection is open to the appropriate server already, but with the wrong
630 * database, it will be switched to the right database and returned, as long as
631 * it has been freed first with reuseConnection().
632 *
633 * On error, returns false, and the connection which caused the
634 * error will be available via $this->mErrorConnection.
635 *
636 * @param int $i Server index
637 * @param string $wiki Wiki ID to open
638 * @return DatabaseBase
639 */
640 function openForeignConnection( $i, $wiki ) {
641 wfProfileIn( __METHOD__ );
642 list( $dbName, $prefix ) = wfSplitWikiID( $wiki );
643 if ( isset( $this->mConns['foreignUsed'][$i][$wiki] ) ) {
644 // Reuse an already-used connection
645 $conn = $this->mConns['foreignUsed'][$i][$wiki];
646 wfDebug( __METHOD__ . ": reusing connection $i/$wiki\n" );
647 } elseif ( isset( $this->mConns['foreignFree'][$i][$wiki] ) ) {
648 // Reuse a free connection for the same wiki
649 $conn = $this->mConns['foreignFree'][$i][$wiki];
650 unset( $this->mConns['foreignFree'][$i][$wiki] );
651 $this->mConns['foreignUsed'][$i][$wiki] = $conn;
652 wfDebug( __METHOD__ . ": reusing free connection $i/$wiki\n" );
653 } elseif ( !empty( $this->mConns['foreignFree'][$i] ) ) {
654 // Reuse a connection from another wiki
655 $conn = reset( $this->mConns['foreignFree'][$i] );
656 $oldWiki = key( $this->mConns['foreignFree'][$i] );
657
658 if ( !$conn->selectDB( $dbName ) ) {
659 $this->mLastError = "Error selecting database $dbName on server " .
660 $conn->getServer() . " from client host " . wfHostname() . "\n";
661 $this->mErrorConnection = $conn;
662 $conn = false;
663 } else {
664 $conn->tablePrefix( $prefix );
665 unset( $this->mConns['foreignFree'][$i][$oldWiki] );
666 $this->mConns['foreignUsed'][$i][$wiki] = $conn;
667 wfDebug( __METHOD__ . ": reusing free connection from $oldWiki for $wiki\n" );
668 }
669 } else {
670 // Open a new connection
671 $server = $this->mServers[$i];
672 $server['serverIndex'] = $i;
673 $server['foreignPoolRefCount'] = 0;
674 $server['foreign'] = true;
675 $conn = $this->reallyOpenConnection( $server, $dbName );
676 if ( !$conn->isOpen() ) {
677 wfDebug( __METHOD__ . ": error opening connection for $i/$wiki\n" );
678 $this->mErrorConnection = $conn;
679 $conn = false;
680 } else {
681 $conn->tablePrefix( $prefix );
682 $this->mConns['foreignUsed'][$i][$wiki] = $conn;
683 wfDebug( __METHOD__ . ": opened new connection for $i/$wiki\n" );
684 }
685 }
686
687 // Increment reference count
688 if ( $conn ) {
689 $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
690 $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
691 }
692 wfProfileOut( __METHOD__ );
693
694 return $conn;
695 }
696
697 /**
698 * Test if the specified index represents an open connection
699 *
700 * @param int $index Server index
701 * @access private
702 * @return bool
703 */
704 function isOpen( $index ) {
705 if ( !is_integer( $index ) ) {
706 return false;
707 }
708
709 return (bool)$this->getAnyOpenConnection( $index );
710 }
711
712 /**
713 * Really opens a connection. Uncached.
714 * Returns a Database object whether or not the connection was successful.
715 * @access private
716 *
717 * @param array $server
718 * @param bool $dbNameOverride
719 * @throws MWException
720 * @return DatabaseBase
721 */
722 function reallyOpenConnection( $server, $dbNameOverride = false ) {
723 if ( !is_array( $server ) ) {
724 throw new MWException( 'You must update your load-balancing configuration. ' .
725 'See DefaultSettings.php entry for $wgDBservers.' );
726 }
727
728 if ( $dbNameOverride !== false ) {
729 $server['dbname'] = $dbNameOverride;
730 }
731
732 # Create object
733 try {
734 $db = DatabaseBase::factory( $server['type'], $server );
735 } catch ( DBConnectionError $e ) {
736 // FIXME: This is probably the ugliest thing I have ever done to
737 // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
738 $db = $e->db;
739 }
740
741 $db->setLBInfo( $server );
742 if ( isset( $server['fakeSlaveLag'] ) ) {
743 $db->setFakeSlaveLag( $server['fakeSlaveLag'] );
744 }
745 if ( isset( $server['fakeMaster'] ) ) {
746 $db->setFakeMaster( true );
747 }
748
749 return $db;
750 }
751
752 /**
753 * @throws DBConnectionError
754 * @return bool
755 */
756 private function reportConnectionError() {
757 $conn = $this->mErrorConnection; // The connection which caused the error
758
759 if ( !is_object( $conn ) ) {
760 // No last connection, probably due to all servers being too busy
761 wfLogDBError( "LB failure with no last connection. Connection error: {$this->mLastError}" );
762
763 // If all servers were busy, mLastError will contain something sensible
764 throw new DBConnectionError( null, $this->mLastError );
765 } else {
766 $server = $conn->getProperty( 'mServer' );
767 wfLogDBError( "Connection error: {$this->mLastError} ({$server})" );
768 $conn->reportConnectionError( "{$this->mLastError} ({$server})" ); // throws DBConnectionError
769 }
770
771 return false; /* not reached */
772 }
773
774 /**
775 * @return int
776 */
777 function getWriterIndex() {
778 return 0;
779 }
780
781 /**
782 * Returns true if the specified index is a valid server index
783 *
784 * @param string $i
785 * @return bool
786 */
787 function haveIndex( $i ) {
788 return array_key_exists( $i, $this->mServers );
789 }
790
791 /**
792 * Returns true if the specified index is valid and has non-zero load
793 *
794 * @param string $i
795 * @return bool
796 */
797 function isNonZeroLoad( $i ) {
798 return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
799 }
800
801 /**
802 * Get the number of defined servers (not the number of open connections)
803 *
804 * @return int
805 */
806 function getServerCount() {
807 return count( $this->mServers );
808 }
809
810 /**
811 * Get the host name or IP address of the server with the specified index
812 * Prefer a readable name if available.
813 * @param string $i
814 * @return string
815 */
816 function getServerName( $i ) {
817 if ( isset( $this->mServers[$i]['hostName'] ) ) {
818 return $this->mServers[$i]['hostName'];
819 } elseif ( isset( $this->mServers[$i]['host'] ) ) {
820 return $this->mServers[$i]['host'];
821 } else {
822 return '';
823 }
824 }
825
826 /**
827 * Return the server info structure for a given index, or false if the index is invalid.
828 * @param int $i
829 * @return array|bool
830 */
831 function getServerInfo( $i ) {
832 if ( isset( $this->mServers[$i] ) ) {
833 return $this->mServers[$i];
834 } else {
835 return false;
836 }
837 }
838
839 /**
840 * Sets the server info structure for the given index. Entry at index $i
841 * is created if it doesn't exist
842 * @param int $i
843 * @param array $serverInfo
844 */
845 function setServerInfo( $i, $serverInfo ) {
846 $this->mServers[$i] = $serverInfo;
847 }
848
849 /**
850 * Get the current master position for chronology control purposes
851 * @return mixed
852 */
853 function getMasterPos() {
854 # If this entire request was served from a slave without opening a connection to the
855 # master (however unlikely that may be), then we can fetch the position from the slave.
856 $masterConn = $this->getAnyOpenConnection( 0 );
857 if ( !$masterConn ) {
858 $serverCount = count( $this->mServers );
859 for ( $i = 1; $i < $serverCount; $i++ ) {
860 $conn = $this->getAnyOpenConnection( $i );
861 if ( $conn ) {
862 wfDebug( "Master pos fetched from slave\n" );
863
864 return $conn->getSlavePos();
865 }
866 }
867 } else {
868 wfDebug( "Master pos fetched from master\n" );
869
870 return $masterConn->getMasterPos();
871 }
872
873 return false;
874 }
875
876 /**
877 * Close all open connections
878 */
879 function closeAll() {
880 foreach ( $this->mConns as $conns2 ) {
881 foreach ( $conns2 as $conns3 ) {
882 /** @var DatabaseBase $conn */
883 foreach ( $conns3 as $conn ) {
884 $conn->close();
885 }
886 }
887 }
888 $this->mConns = array(
889 'local' => array(),
890 'foreignFree' => array(),
891 'foreignUsed' => array(),
892 );
893 }
894
895 /**
896 * Close a connection
897 * Using this function makes sure the LoadBalancer knows the connection is closed.
898 * If you use $conn->close() directly, the load balancer won't update its state.
899 * @param DatabaseBase $conn
900 */
901 function closeConnection( $conn ) {
902 $done = false;
903 foreach ( $this->mConns as $i1 => $conns2 ) {
904 foreach ( $conns2 as $i2 => $conns3 ) {
905 foreach ( $conns3 as $i3 => $candidateConn ) {
906 if ( $conn === $candidateConn ) {
907 $conn->close();
908 unset( $this->mConns[$i1][$i2][$i3] );
909 $done = true;
910 break;
911 }
912 }
913 }
914 }
915 if ( !$done ) {
916 $conn->close();
917 }
918 }
919
920 /**
921 * Commit transactions on all open connections
922 */
923 function commitAll() {
924 foreach ( $this->mConns as $conns2 ) {
925 foreach ( $conns2 as $conns3 ) {
926 /** @var DatabaseBase[] $conns3 */
927 foreach ( $conns3 as $conn ) {
928 if ( $conn->trxLevel() ) {
929 $conn->commit( __METHOD__, 'flush' );
930 }
931 }
932 }
933 }
934 }
935
936 /**
937 * Issue COMMIT only on master, only if queries were done on connection
938 */
939 function commitMasterChanges() {
940 // Always 0, but who knows.. :)
941 $masterIndex = $this->getWriterIndex();
942 foreach ( $this->mConns as $conns2 ) {
943 if ( empty( $conns2[$masterIndex] ) ) {
944 continue;
945 }
946 /** @var DatabaseBase $conn */
947 foreach ( $conns2[$masterIndex] as $conn ) {
948 if ( $conn->trxLevel() && $conn->writesOrCallbacksPending() ) {
949 $conn->commit( __METHOD__, 'flush' );
950 }
951 }
952 }
953 }
954
955 /**
956 * Issue ROLLBACK only on master, only if queries were done on connection
957 * @since 1.23
958 */
959 function rollbackMasterChanges() {
960 // Always 0, but who knows.. :)
961 $masterIndex = $this->getWriterIndex();
962 foreach ( $this->mConns as $conns2 ) {
963 if ( empty( $conns2[$masterIndex] ) ) {
964 continue;
965 }
966 /** @var DatabaseBase $conn */
967 foreach ( $conns2[$masterIndex] as $conn ) {
968 if ( $conn->trxLevel() && $conn->writesOrCallbacksPending() ) {
969 $conn->rollback( __METHOD__, 'flush' );
970 }
971 }
972 }
973 }
974
975 /**
976 * @return bool Whether a master connection is already open
977 * @since 1.24
978 */
979 function hasMasterConnection() {
980 return $this->isOpen( $this->getWriterIndex() );
981 }
982
983 /**
984 * Determine if there are any pending changes that need to be rolled back
985 * or committed.
986 * @since 1.23
987 * @return bool
988 */
989 function hasMasterChanges() {
990 // Always 0, but who knows.. :)
991 $masterIndex = $this->getWriterIndex();
992 foreach ( $this->mConns as $conns2 ) {
993 if ( empty( $conns2[$masterIndex] ) ) {
994 continue;
995 }
996 /** @var DatabaseBase $conn */
997 foreach ( $conns2[$masterIndex] as $conn ) {
998 if ( $conn->trxLevel() && $conn->writesOrCallbacksPending() ) {
999 return true;
1000 }
1001 }
1002 }
1003 return false;
1004 }
1005
1006 /**
1007 * @param mixed $value
1008 * @return mixed
1009 */
1010 function waitTimeout( $value = null ) {
1011 return wfSetVar( $this->mWaitTimeout, $value );
1012 }
1013
1014 /**
1015 * @return bool
1016 */
1017 function getLaggedSlaveMode() {
1018 return $this->mLaggedSlaveMode;
1019 }
1020
1021 /**
1022 * Disables/enables lag checks
1023 * @param null|bool $mode
1024 * @return bool
1025 */
1026 function allowLagged( $mode = null ) {
1027 if ( $mode === null ) {
1028 return $this->mAllowLagged;
1029 }
1030 $this->mAllowLagged = $mode;
1031
1032 return $this->mAllowLagged;
1033 }
1034
1035 /**
1036 * @return bool
1037 */
1038 function pingAll() {
1039 $success = true;
1040 foreach ( $this->mConns as $conns2 ) {
1041 foreach ( $conns2 as $conns3 ) {
1042 /** @var DatabaseBase[] $conns3 */
1043 foreach ( $conns3 as $conn ) {
1044 if ( !$conn->ping() ) {
1045 $success = false;
1046 }
1047 }
1048 }
1049 }
1050
1051 return $success;
1052 }
1053
1054 /**
1055 * Call a function with each open connection object
1056 * @param callable $callback
1057 * @param array $params
1058 */
1059 function forEachOpenConnection( $callback, $params = array() ) {
1060 foreach ( $this->mConns as $conns2 ) {
1061 foreach ( $conns2 as $conns3 ) {
1062 foreach ( $conns3 as $conn ) {
1063 $mergedParams = array_merge( array( $conn ), $params );
1064 call_user_func_array( $callback, $mergedParams );
1065 }
1066 }
1067 }
1068 }
1069
1070 /**
1071 * Get the hostname and lag time of the most-lagged slave
1072 *
1073 * This is useful for maintenance scripts that need to throttle their updates.
1074 * May attempt to open connections to slaves on the default DB. If there is
1075 * no lag, the maximum lag will be reported as -1.
1076 *
1077 * @param bool|string $wiki Wiki ID, or false for the default database
1078 * @return array ( host, max lag, index of max lagged host )
1079 */
1080 function getMaxLag( $wiki = false ) {
1081 $maxLag = -1;
1082 $host = '';
1083 $maxIndex = 0;
1084
1085 if ( $this->getServerCount() <= 1 ) {
1086 return array( $host, $maxLag, $maxIndex ); // no replication = no lag
1087 }
1088
1089 $lagTimes = $this->getLagTimes( $wiki );
1090 foreach ( $lagTimes as $i => $lag ) {
1091 if ( $lag > $maxLag ) {
1092 $maxLag = $lag;
1093 $host = $this->mServers[$i]['host'];
1094 $maxIndex = $i;
1095 }
1096 }
1097
1098 return array( $host, $maxLag, $maxIndex );
1099 }
1100
1101 /**
1102 * Get lag time for each server
1103 *
1104 * Results are cached for a short time in memcached/process cache
1105 *
1106 * @param string|bool $wiki
1107 * @return array Map of (server index => seconds)
1108 */
1109 function getLagTimes( $wiki = false ) {
1110 if ( $this->getServerCount() <= 1 ) {
1111 return array( 0 => 0 ); // no replication = no lag
1112 }
1113
1114 if ( $this->mProcCache->has( 'slave_lag', 'times', 1 ) ) {
1115 return $this->mProcCache->get( 'slave_lag', 'times' );
1116 }
1117
1118 # Send the request to the load monitor
1119 $times = $this->getLoadMonitor()->getLagTimes( array_keys( $this->mServers ), $wiki );
1120
1121 $this->mProcCache->set( 'slave_lag', 'times', $times );
1122
1123 return $times;
1124 }
1125
1126 /**
1127 * Get the lag in seconds for a given connection, or zero if this load
1128 * balancer does not have replication enabled.
1129 *
1130 * This should be used in preference to Database::getLag() in cases where
1131 * replication may not be in use, since there is no way to determine if
1132 * replication is in use at the connection level without running
1133 * potentially restricted queries such as SHOW SLAVE STATUS. Using this
1134 * function instead of Database::getLag() avoids a fatal error in this
1135 * case on many installations.
1136 *
1137 * @param DatabaseBase $conn
1138 * @return int
1139 */
1140 function safeGetLag( $conn ) {
1141 if ( $this->getServerCount() == 1 ) {
1142 return 0;
1143 } else {
1144 return $conn->getLag();
1145 }
1146 }
1147
1148 /**
1149 * Clear the cache for slag lag delay times
1150 */
1151 function clearLagTimeCache() {
1152 $this->mProcCache->clear( 'slave_lag' );
1153 }
1154 }
1155
1156 /**
1157 * Helper class to handle automatically marking connections as reusable (via RAII pattern)
1158 * as well handling deferring the actual network connection until the handle is used
1159 *
1160 * @ingroup Database
1161 * @since 1.22
1162 */
1163 class DBConnRef implements IDatabase {
1164 /** @var LoadBalancer */
1165 protected $lb;
1166
1167 /** @var DatabaseBase|null */
1168 protected $conn;
1169
1170 /** @var array|null */
1171 protected $params;
1172
1173 /**
1174 * @param LoadBalancer $lb
1175 * @param DatabaseBase|array $conn Connection or (server index, group, wiki ID) array
1176 */
1177 public function __construct( LoadBalancer $lb, $conn ) {
1178 $this->lb = $lb;
1179 if ( $conn instanceof DatabaseBase ) {
1180 $this->conn = $conn;
1181 } else {
1182 $this->params = $conn;
1183 }
1184 }
1185
1186 public function __call( $name, $arguments ) {
1187 if ( $this->conn === null ) {
1188 list( $db, $groups, $wiki ) = $this->params;
1189 $this->conn = $this->lb->getConnection( $db, $groups, $wiki );
1190 }
1191
1192 return call_user_func_array( array( $this->conn, $name ), $arguments );
1193 }
1194
1195 function __destruct() {
1196 if ( $this->conn !== null ) {
1197 $this->lb->reuseConnection( $this->conn );
1198 }
1199 }
1200 }
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