--- /dev/null
+<?php
+/**
+ * Database load balancing manager
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Database
+ */
+namespace Wikimedia\Rdbms;
+
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+use Wikimedia\ScopedCallback;
+use BagOStuff;
+use EmptyBagOStuff;
+use WANObjectCache;
+use ArrayUtils;
+use InvalidArgumentException;
+use RuntimeException;
+use Exception;
+
+/**
+ * Database connection, tracking, load balancing, and transaction manager for a cluster
+ *
+ * @ingroup Database
+ */
+class LoadBalancer implements ILoadBalancer {
+ /** @var array[] Map of (server index => server config array) */
+ private $mServers;
+ /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
+ private $mConns;
+ /** @var float[] Map of (server index => weight) */
+ private $mLoads;
+ /** @var array[] Map of (group => server index => weight) */
+ private $mGroupLoads;
+ /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */
+ private $mAllowLagged;
+ /** @var int Seconds to spend waiting on replica DB lag to resolve */
+ private $mWaitTimeout;
+ /** @var array The LoadMonitor configuration */
+ private $loadMonitorConfig;
+ /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
+ private $tableAliases = [];
+
+ /** @var ILoadMonitor */
+ private $loadMonitor;
+ /** @var ChronologyProtector|null */
+ private $chronProt;
+ /** @var BagOStuff */
+ private $srvCache;
+ /** @var WANObjectCache */
+ private $wanCache;
+ /** @var object|string Class name or object With profileIn/profileOut methods */
+ protected $profiler;
+ /** @var TransactionProfiler */
+ protected $trxProfiler;
+ /** @var LoggerInterface */
+ protected $replLogger;
+ /** @var LoggerInterface */
+ protected $connLogger;
+ /** @var LoggerInterface */
+ protected $queryLogger;
+ /** @var LoggerInterface */
+ protected $perfLogger;
+
+ /** @var Database DB connection object that caused a problem */
+ private $errorConnection;
+ /** @var int The generic (not query grouped) replica DB index (of $mServers) */
+ private $mReadIndex;
+ /** @var bool|DBMasterPos False if not set */
+ private $mWaitForPos;
+ /** @var bool Whether the generic reader fell back to a lagged replica DB */
+ private $laggedReplicaMode = false;
+ /** @var bool Whether the generic reader fell back to a lagged replica DB */
+ private $allReplicasDownMode = false;
+ /** @var string The last DB selection or connection error */
+ private $mLastError = 'Unknown error';
+ /** @var string|bool Reason the LB is read-only or false if not */
+ private $readOnlyReason = false;
+ /** @var int Total connections opened */
+ private $connsOpened = 0;
+ /** @var string|bool String if a requested DBO_TRX transaction round is active */
+ private $trxRoundId = false;
+ /** @var array[] Map of (name => callable) */
+ private $trxRecurringCallbacks = [];
+ /** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
+ private $localDomain;
+ /** @var string Alternate ID string for the domain instead of DatabaseDomain::getId() */
+ private $localDomainIdAlias;
+ /** @var string Current server name */
+ private $host;
+ /** @var bool Whether this PHP instance is for a CLI script */
+ protected $cliMode;
+ /** @var string Agent name for query profiling */
+ protected $agent;
+
+ /** @var callable Exception logger */
+ private $errorLogger;
+
+ /** @var bool */
+ private $disabled = false;
+ /** @var bool */
+ private $chronProtInitialized = false;
+
+ /** @var int Warn when this many connection are held */
+ const CONN_HELD_WARN_THRESHOLD = 10;
+
+ /** @var int Default 'max lag' when unspecified */
+ const MAX_LAG_DEFAULT = 10;
+ /** @var int Seconds to cache master server read-only status */
+ const TTL_CACHE_READONLY = 5;
+
+ const KEY_LOCAL = 'local';
+ const KEY_FOREIGN_FREE = 'foreignFree';
+ const KEY_FOREIGN_INUSE = 'foreignInUse';
+
+ const KEY_LOCAL_NOROUND = 'localAutoCommit';
+ const KEY_FOREIGN_FREE_NOROUND = 'foreignFreeAutoCommit';
+ const KEY_FOREIGN_INUSE_NOROUND = 'foreignInUseAutoCommit';
+
+ public function __construct( array $params ) {
+ if ( !isset( $params['servers'] ) ) {
+ throw new InvalidArgumentException( __CLASS__ . ': missing servers parameter' );
+ }
+ $this->mServers = $params['servers'];
+ foreach ( $this->mServers as $i => $server ) {
+ if ( $i == 0 ) {
+ $this->mServers[$i]['master'] = true;
+ } else {
+ $this->mServers[$i]['replica'] = true;
+ }
+ }
+
+ $this->localDomain = isset( $params['localDomain'] )
+ ? DatabaseDomain::newFromId( $params['localDomain'] )
+ : DatabaseDomain::newUnspecified();
+ // In case a caller assumes that the domain ID is simply <db>-<prefix>, which is almost
+ // always true, gracefully handle the case when they fail to account for escaping.
+ if ( $this->localDomain->getTablePrefix() != '' ) {
+ $this->localDomainIdAlias =
+ $this->localDomain->getDatabase() . '-' . $this->localDomain->getTablePrefix();
+ } else {
+ $this->localDomainIdAlias = $this->localDomain->getDatabase();
+ }
+
+ $this->mWaitTimeout = isset( $params['waitTimeout'] ) ? $params['waitTimeout'] : 10;
+
+ $this->mReadIndex = -1;
+ $this->mConns = [
+ // Connection were transaction rounds may be applied
+ self::KEY_LOCAL => [],
+ self::KEY_FOREIGN_INUSE => [],
+ self::KEY_FOREIGN_FREE => [],
+ // Auto-committing counterpart connections that ignore transaction rounds
+ self::KEY_LOCAL_NOROUND => [],
+ self::KEY_FOREIGN_INUSE_NOROUND => [],
+ self::KEY_FOREIGN_FREE_NOROUND => []
+ ];
+ $this->mLoads = [];
+ $this->mWaitForPos = false;
+ $this->mAllowLagged = false;
+
+ if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
+ $this->readOnlyReason = $params['readOnlyReason'];
+ }
+
+ if ( isset( $params['loadMonitor'] ) ) {
+ $this->loadMonitorConfig = $params['loadMonitor'];
+ } else {
+ $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ];
+ }
+
+ foreach ( $params['servers'] as $i => $server ) {
+ $this->mLoads[$i] = $server['load'];
+ if ( isset( $server['groupLoads'] ) ) {
+ foreach ( $server['groupLoads'] as $group => $ratio ) {
+ if ( !isset( $this->mGroupLoads[$group] ) ) {
+ $this->mGroupLoads[$group] = [];
+ }
+ $this->mGroupLoads[$group][$i] = $ratio;
+ }
+ }
+ }
+
+ if ( isset( $params['srvCache'] ) ) {
+ $this->srvCache = $params['srvCache'];
+ } else {
+ $this->srvCache = new EmptyBagOStuff();
+ }
+ if ( isset( $params['wanCache'] ) ) {
+ $this->wanCache = $params['wanCache'];
+ } else {
+ $this->wanCache = WANObjectCache::newEmpty();
+ }
+ $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
+ if ( isset( $params['trxProfiler'] ) ) {
+ $this->trxProfiler = $params['trxProfiler'];
+ } else {
+ $this->trxProfiler = new TransactionProfiler();
+ }
+
+ $this->errorLogger = isset( $params['errorLogger'] )
+ ? $params['errorLogger']
+ : function ( Exception $e ) {
+ trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
+ };
+
+ foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
+ $this->$key = isset( $params[$key] ) ? $params[$key] : new NullLogger();
+ }
+
+ $this->host = isset( $params['hostname'] )
+ ? $params['hostname']
+ : ( gethostname() ?: 'unknown' );
+ $this->cliMode = isset( $params['cliMode'] ) ? $params['cliMode'] : PHP_SAPI === 'cli';
+ $this->agent = isset( $params['agent'] ) ? $params['agent'] : '';
+
+ if ( isset( $params['chronologyProtector'] ) ) {
+ $this->chronProt = $params['chronologyProtector'];
+ }
+ }
+
+ /**
+ * Get a LoadMonitor instance
+ *
+ * @return ILoadMonitor
+ */
+ private function getLoadMonitor() {
+ if ( !isset( $this->loadMonitor ) ) {
+ $compat = [
+ 'LoadMonitor' => LoadMonitor::class,
+ 'LoadMonitorNull' => LoadMonitorNull::class,
+ 'LoadMonitorMySQL' => LoadMonitorMySQL::class,
+ ];
+
+ $class = $this->loadMonitorConfig['class'];
+ if ( isset( $compat[$class] ) ) {
+ $class = $compat[$class];
+ }
+
+ $this->loadMonitor = new $class(
+ $this, $this->srvCache, $this->wanCache, $this->loadMonitorConfig );
+ $this->loadMonitor->setLogger( $this->replLogger );
+ }
+
+ return $this->loadMonitor;
+ }
+
+ /**
+ * @param array $loads
+ * @param bool|string $domain Domain to get non-lagged for
+ * @param int $maxLag Restrict the maximum allowed lag to this many seconds
+ * @return bool|int|string
+ */
+ private function getRandomNonLagged( array $loads, $domain = false, $maxLag = INF ) {
+ $lags = $this->getLagTimes( $domain );
+
+ # Unset excessively lagged servers
+ foreach ( $lags as $i => $lag ) {
+ if ( $i != 0 ) {
+ # How much lag this server nominally is allowed to have
+ $maxServerLag = isset( $this->mServers[$i]['max lag'] )
+ ? $this->mServers[$i]['max lag']
+ : self::MAX_LAG_DEFAULT; // default
+ # Constrain that futher by $maxLag argument
+ $maxServerLag = min( $maxServerLag, $maxLag );
+
+ $host = $this->getServerName( $i );
+ if ( $lag === false && !is_infinite( $maxServerLag ) ) {
+ $this->replLogger->error(
+ "Server {host} is not replicating?", [ 'host' => $host ] );
+ unset( $loads[$i] );
+ } elseif ( $lag > $maxServerLag ) {
+ $this->replLogger->debug(
+ __METHOD__ .
+ ": server {host} has {lag} seconds of lag (>= {maxlag})",
+ [ 'host' => $host, 'lag' => $lag, 'maxlag' => $maxServerLag ]
+ );
+ unset( $loads[$i] );
+ }
+ }
+ }
+
+ # Find out if all the replica DBs with non-zero load are lagged
+ $sum = 0;
+ foreach ( $loads as $load ) {
+ $sum += $load;
+ }
+ if ( $sum == 0 ) {
+ # No appropriate DB servers except maybe the master and some replica DBs with zero load
+ # Do NOT use the master
+ # Instead, this function will return false, triggering read-only mode,
+ # and a lagged replica DB will be used instead.
+ return false;
+ }
+
+ if ( count( $loads ) == 0 ) {
+ return false;
+ }
+
+ # Return a random representative of the remainder
+ return ArrayUtils::pickRandom( $loads );
+ }
+
+ public function getReaderIndex( $group = false, $domain = false ) {
+ if ( count( $this->mServers ) == 1 ) {
+ // Skip the load balancing if there's only one server
+ return $this->getWriterIndex();
+ } elseif ( $group === false && $this->mReadIndex >= 0 ) {
+ // Shortcut if the generic reader index was already cached
+ return $this->mReadIndex;
+ }
+
+ if ( $group !== false ) {
+ // Use the server weight array for this load group
+ if ( isset( $this->mGroupLoads[$group] ) ) {
+ $loads = $this->mGroupLoads[$group];
+ } else {
+ // No loads for this group, return false and the caller can use some other group
+ $this->connLogger->info( __METHOD__ . ": no loads for group $group" );
+
+ return false;
+ }
+ } else {
+ // Use the generic load group
+ $loads = $this->mLoads;
+ }
+
+ // Scale the configured load ratios according to each server's load and state
+ $this->getLoadMonitor()->scaleLoads( $loads, $domain );
+
+ // Pick a server to use, accounting for weights, load, lag, and mWaitForPos
+ list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
+ if ( $i === false ) {
+ // Replica DB connection unsuccessful
+ return false;
+ }
+
+ if ( $this->mWaitForPos && $i != $this->getWriterIndex() ) {
+ // Before any data queries are run, wait for the server to catch up to the
+ // specified position. This is used to improve session consistency. Note that
+ // when LoadBalancer::waitFor() sets mWaitForPos, the waiting triggers here,
+ // so update laggedReplicaMode as needed for consistency.
+ if ( !$this->doWait( $i ) ) {
+ $laggedReplicaMode = true;
+ }
+ }
+
+ if ( $this->mReadIndex <= 0 && $this->mLoads[$i] > 0 && $group === false ) {
+ // Cache the generic reader index for future ungrouped DB_REPLICA handles
+ $this->mReadIndex = $i;
+ // Record if the generic reader index is in "lagged replica DB" mode
+ if ( $laggedReplicaMode ) {
+ $this->laggedReplicaMode = true;
+ }
+ }
+
+ $serverName = $this->getServerName( $i );
+ $this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
+
+ return $i;
+ }
+
+ /**
+ * @param array $loads List of server weights
+ * @param string|bool $domain
+ * @return array (reader index, lagged replica mode) or false on failure
+ */
+ private function pickReaderIndex( array $loads, $domain = false ) {
+ if ( !count( $loads ) ) {
+ throw new InvalidArgumentException( "Empty server array given to LoadBalancer" );
+ }
+
+ /** @var int|bool $i Index of selected server */
+ $i = false;
+ /** @var bool $laggedReplicaMode Whether server is considered lagged */
+ $laggedReplicaMode = false;
+
+ // Quickly look through the available servers for a server that meets criteria...
+ $currentLoads = $loads;
+ while ( count( $currentLoads ) ) {
+ if ( $this->mAllowLagged || $laggedReplicaMode ) {
+ $i = ArrayUtils::pickRandom( $currentLoads );
+ } else {
+ $i = false;
+ if ( $this->mWaitForPos && $this->mWaitForPos->asOfTime() ) {
+ // ChronologyProtecter sets mWaitForPos for session consistency.
+ // This triggers doWait() after connect, so it's especially good to
+ // avoid lagged servers so as to avoid excessive delay in that method.
+ $ago = microtime( true ) - $this->mWaitForPos->asOfTime();
+ // Aim for <= 1 second of waiting (being too picky can backfire)
+ $i = $this->getRandomNonLagged( $currentLoads, $domain, $ago + 1 );
+ }
+ if ( $i === false ) {
+ // Any server with less lag than it's 'max lag' param is preferable
+ $i = $this->getRandomNonLagged( $currentLoads, $domain );
+ }
+ if ( $i === false && count( $currentLoads ) != 0 ) {
+ // All replica DBs lagged. Switch to read-only mode
+ $this->replLogger->error( "All replica DBs lagged. Switch to read-only mode" );
+ $i = ArrayUtils::pickRandom( $currentLoads );
+ $laggedReplicaMode = true;
+ }
+ }
+
+ if ( $i === false ) {
+ // pickRandom() returned false.
+ // This is permanent and means the configuration or the load monitor
+ // wants us to return false.
+ $this->connLogger->debug( __METHOD__ . ": pickRandom() returned false" );
+
+ return [ false, false ];
+ }
+
+ $serverName = $this->getServerName( $i );
+ $this->connLogger->debug( __METHOD__ . ": Using reader #$i: $serverName..." );
+
+ $conn = $this->openConnection( $i, $domain );
+ if ( !$conn ) {
+ $this->connLogger->warning( __METHOD__ . ": Failed connecting to $i/$domain" );
+ unset( $currentLoads[$i] ); // avoid this server next iteration
+ $i = false;
+ continue;
+ }
+
+ // Decrement reference counter, we are finished with this connection.
+ // It will be incremented for the caller later.
+ if ( $domain !== false ) {
+ $this->reuseConnection( $conn );
+ }
+
+ // Return this server
+ break;
+ }
+
+ // If all servers were down, quit now
+ if ( !count( $currentLoads ) ) {
+ $this->connLogger->error( "All servers down" );
+ }
+
+ return [ $i, $laggedReplicaMode ];
+ }
+
+ public function waitFor( $pos ) {
+ $oldPos = $this->mWaitForPos;
+ try {
+ $this->mWaitForPos = $pos;
+ // If a generic reader connection was already established, then wait now
+ $i = $this->mReadIndex;
+ if ( $i > 0 ) {
+ if ( !$this->doWait( $i ) ) {
+ $this->laggedReplicaMode = true;
+ }
+ }
+ } finally {
+ // Restore the older position if it was higher since this is used for lag-protection
+ $this->setWaitForPositionIfHigher( $oldPos );
+ }
+ }
+
+ public function waitForOne( $pos, $timeout = null ) {
+ $oldPos = $this->mWaitForPos;
+ try {
+ $this->mWaitForPos = $pos;
+
+ $i = $this->mReadIndex;
+ if ( $i <= 0 ) {
+ // Pick a generic replica DB if there isn't one yet
+ $readLoads = $this->mLoads;
+ unset( $readLoads[$this->getWriterIndex()] ); // replica DBs only
+ $readLoads = array_filter( $readLoads ); // with non-zero load
+ $i = ArrayUtils::pickRandom( $readLoads );
+ }
+
+ if ( $i > 0 ) {
+ $ok = $this->doWait( $i, true, $timeout );
+ } else {
+ $ok = true; // no applicable loads
+ }
+ } finally {
+ # Restore the old position, as this is not used for lag-protection but for throttling
+ $this->mWaitForPos = $oldPos;
+ }
+
+ return $ok;
+ }
+
+ public function waitForAll( $pos, $timeout = null ) {
+ $oldPos = $this->mWaitForPos;
+ try {
+ $this->mWaitForPos = $pos;
+ $serverCount = count( $this->mServers );
+
+ $ok = true;
+ for ( $i = 1; $i < $serverCount; $i++ ) {
+ if ( $this->mLoads[$i] > 0 ) {
+ $ok = $this->doWait( $i, true, $timeout ) && $ok;
+ }
+ }
+ } finally {
+ # Restore the old position, as this is not used for lag-protection but for throttling
+ $this->mWaitForPos = $oldPos;
+ }
+
+ return $ok;
+ }
+
+ /**
+ * @param DBMasterPos|bool $pos
+ */
+ private function setWaitForPositionIfHigher( $pos ) {
+ if ( !$pos ) {
+ return;
+ }
+
+ if ( !$this->mWaitForPos || $pos->hasReached( $this->mWaitForPos ) ) {
+ $this->mWaitForPos = $pos;
+ }
+ }
+
+ /**
+ * @param int $i
+ * @return IDatabase|bool
+ */
+ public function getAnyOpenConnection( $i ) {
+ foreach ( $this->mConns as $connsByServer ) {
+ if ( !empty( $connsByServer[$i] ) ) {
+ /** @var IDatabase[] $serverConns */
+ $serverConns = $connsByServer[$i];
+
+ return reset( $serverConns );
+ }
+ }
+
+ return false;
+ }
+
+ /**
+ * Wait for a given replica DB to catch up to the master pos stored in $this
+ * @param int $index Server index
+ * @param bool $open Check the server even if a new connection has to be made
+ * @param int $timeout Max seconds to wait; default is mWaitTimeout
+ * @return bool
+ */
+ protected function doWait( $index, $open = false, $timeout = null ) {
+ $close = false; // close the connection afterwards
+
+ // Check if we already know that the DB has reached this point
+ $server = $this->getServerName( $index );
+ $key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $server, 'v1' );
+ /** @var DBMasterPos $knownReachedPos */
+ $knownReachedPos = $this->srvCache->get( $key );
+ if (
+ $knownReachedPos instanceof DBMasterPos &&
+ $knownReachedPos->hasReached( $this->mWaitForPos )
+ ) {
+ $this->replLogger->debug( __METHOD__ .
+ ": replica DB $server known to be caught up (pos >= $knownReachedPos)." );
+ return true;
+ }
+
+ // Find a connection to wait on, creating one if needed and allowed
+ $conn = $this->getAnyOpenConnection( $index );
+ if ( !$conn ) {
+ if ( !$open ) {
+ $this->replLogger->debug( __METHOD__ . ": no connection open for $server" );
+
+ return false;
+ } else {
+ $conn = $this->openConnection( $index, self::DOMAIN_ANY );
+ if ( !$conn ) {
+ $this->replLogger->warning( __METHOD__ . ": failed to connect to $server" );
+
+ return false;
+ }
+ // Avoid connection spam in waitForAll() when connections
+ // are made just for the sake of doing this lag check.
+ $close = true;
+ }
+ }
+
+ $this->replLogger->info( __METHOD__ . ": Waiting for replica DB $server to catch up..." );
+ $timeout = $timeout ?: $this->mWaitTimeout;
+ $result = $conn->masterPosWait( $this->mWaitForPos, $timeout );
+
+ if ( $result == -1 || is_null( $result ) ) {
+ // Timed out waiting for replica DB, use master instead
+ $this->replLogger->warning(
+ __METHOD__ . ": Timed out waiting on {host} pos {$this->mWaitForPos}",
+ [ 'host' => $server ]
+ );
+ $ok = false;
+ } else {
+ $this->replLogger->info( __METHOD__ . ": Done" );
+ $ok = true;
+ // Remember that the DB reached this point
+ $this->srvCache->set( $key, $this->mWaitForPos, BagOStuff::TTL_DAY );
+ }
+
+ if ( $close ) {
+ $this->closeConnection( $conn );
+ }
+
+ return $ok;
+ }
+
+ public function getConnection( $i, $groups = [], $domain = false, $flags = 0 ) {
+ if ( $i === null || $i === false ) {
+ throw new InvalidArgumentException( 'Attempt to call ' . __METHOD__ .
+ ' with invalid server index' );
+ }
+
+ if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
+ $domain = false; // local connection requested
+ }
+
+ $groups = ( $groups === false || $groups === [] )
+ ? [ false ] // check one "group": the generic pool
+ : (array)$groups;
+
+ $masterOnly = ( $i == self::DB_MASTER || $i == $this->getWriterIndex() );
+ $oldConnsOpened = $this->connsOpened; // connections open now
+
+ if ( $i == self::DB_MASTER ) {
+ $i = $this->getWriterIndex();
+ } else {
+ # Try to find an available server in any the query groups (in order)
+ foreach ( $groups as $group ) {
+ $groupIndex = $this->getReaderIndex( $group, $domain );
+ if ( $groupIndex !== false ) {
+ $i = $groupIndex;
+ break;
+ }
+ }
+ }
+
+ # Operation-based index
+ if ( $i == self::DB_REPLICA ) {
+ $this->mLastError = 'Unknown error'; // reset error string
+ # Try the general server pool if $groups are unavailable.
+ $i = ( $groups === [ false ] )
+ ? false // don't bother with this if that is what was tried above
+ : $this->getReaderIndex( false, $domain );
+ # Couldn't find a working server in getReaderIndex()?
+ if ( $i === false ) {
+ $this->mLastError = 'No working replica DB server: ' . $this->mLastError;
+ // Throw an exception
+ $this->reportConnectionError();
+ return null; // not reached
+ }
+ }
+
+ # Now we have an explicit index into the servers array
+ $conn = $this->openConnection( $i, $domain, $flags );
+ if ( !$conn ) {
+ // Throw an exception
+ $this->reportConnectionError();
+ return null; // not reached
+ }
+
+ # Profile any new connections that happen
+ if ( $this->connsOpened > $oldConnsOpened ) {
+ $host = $conn->getServer();
+ $dbname = $conn->getDBname();
+ $this->trxProfiler->recordConnection( $host, $dbname, $masterOnly );
+ }
+
+ if ( $masterOnly ) {
+ # Make master-requested DB handles inherit any read-only mode setting
+ $conn->setLBInfo( 'readOnlyReason', $this->getReadOnlyReason( $domain, $conn ) );
+ }
+
+ return $conn;
+ }
+
+ public function reuseConnection( $conn ) {
+ $serverIndex = $conn->getLBInfo( 'serverIndex' );
+ $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
+ if ( $serverIndex === null || $refCount === null ) {
+ /**
+ * This can happen in code like:
+ * foreach ( $dbs as $db ) {
+ * $conn = $lb->getConnection( $lb::DB_REPLICA, [], $db );
+ * ...
+ * $lb->reuseConnection( $conn );
+ * }
+ * When a connection to the local DB is opened in this way, reuseConnection()
+ * should be ignored
+ */
+ return;
+ } elseif ( $conn instanceof DBConnRef ) {
+ // DBConnRef already handles calling reuseConnection() and only passes the live
+ // Database instance to this method. Any caller passing in a DBConnRef is broken.
+ $this->connLogger->error( __METHOD__ . ": got DBConnRef instance.\n" .
+ ( new RuntimeException() )->getTraceAsString() );
+
+ return;
+ }
+
+ if ( $this->disabled ) {
+ return; // DBConnRef handle probably survived longer than the LoadBalancer
+ }
+
+ if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
+ $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
+ $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
+ } else {
+ $connFreeKey = self::KEY_FOREIGN_FREE;
+ $connInUseKey = self::KEY_FOREIGN_INUSE;
+ }
+
+ $domain = $conn->getDomainID();
+ if ( !isset( $this->mConns[$connInUseKey][$serverIndex][$domain] ) ) {
+ throw new InvalidArgumentException( __METHOD__ .
+ ": connection $serverIndex/$domain not found; it may have already been freed." );
+ } elseif ( $this->mConns[$connInUseKey][$serverIndex][$domain] !== $conn ) {
+ throw new InvalidArgumentException( __METHOD__ .
+ ": connection $serverIndex/$domain mismatched; it may have already been freed." );
+ }
+
+ $conn->setLBInfo( 'foreignPoolRefCount', --$refCount );
+ if ( $refCount <= 0 ) {
+ $this->mConns[$connFreeKey][$serverIndex][$domain] = $conn;
+ unset( $this->mConns[$connInUseKey][$serverIndex][$domain] );
+ if ( !$this->mConns[$connInUseKey][$serverIndex] ) {
+ unset( $this->mConns[$connInUseKey][$serverIndex] ); // clean up
+ }
+ $this->connLogger->debug( __METHOD__ . ": freed connection $serverIndex/$domain" );
+ } else {
+ $this->connLogger->debug( __METHOD__ .
+ ": reference count for $serverIndex/$domain reduced to $refCount" );
+ }
+ }
+
+ public function getConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
+ $domain = ( $domain !== false ) ? $domain : $this->localDomain;
+
+ return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
+ }
+
+ public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
+ $domain = ( $domain !== false ) ? $domain : $this->localDomain;
+
+ return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
+ }
+
+ public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
+ $domain = ( $domain !== false ) ? $domain : $this->localDomain;
+
+ return new MaintainableDBConnRef(
+ $this, $this->getConnection( $db, $groups, $domain, $flags ) );
+ }
+
+ public function openConnection( $i, $domain = false, $flags = 0 ) {
+ if ( $this->localDomain->equals( $domain ) || $domain === $this->localDomainIdAlias ) {
+ $domain = false; // local connection requested
+ }
+
+ if ( !$this->chronProtInitialized && $this->chronProt ) {
+ $this->connLogger->debug( __METHOD__ . ': calling initLB() before first connection.' );
+ // Load CP positions before connecting so that doWait() triggers later if needed
+ $this->chronProtInitialized = true;
+ $this->chronProt->initLB( $this );
+ }
+
+ // Check if an auto-commit connection is being requested. If so, it will not reuse the
+ // main set of DB connections but rather its own pool since:
+ // a) those are usually set to implicitly use transaction rounds via DBO_TRX
+ // b) those must support the use of explicit transaction rounds via beginMasterChanges()
+ $autoCommit = ( ( $flags & self::CONN_TRX_AUTO ) == self::CONN_TRX_AUTO );
+
+ if ( $domain !== false ) {
+ // Connection is to a foreign domain
+ $conn = $this->openForeignConnection( $i, $domain, $flags );
+ } else {
+ // Connection is to the local domain
+ $connKey = $autoCommit ? self::KEY_LOCAL_NOROUND : self::KEY_LOCAL;
+ if ( isset( $this->mConns[$connKey][$i][0] ) ) {
+ $conn = $this->mConns[$connKey][$i][0];
+ } else {
+ if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
+ throw new InvalidArgumentException( "No server with index '$i'." );
+ }
+ // Open a new connection
+ $server = $this->mServers[$i];
+ $server['serverIndex'] = $i;
+ $server['autoCommitOnly'] = $autoCommit;
+ $conn = $this->reallyOpenConnection( $server, false );
+ $host = $this->getServerName( $i );
+ if ( $conn->isOpen() ) {
+ $this->connLogger->debug( "Connected to database $i at '$host'." );
+ $this->mConns[$connKey][$i][0] = $conn;
+ } else {
+ $this->connLogger->warning( "Failed to connect to database $i at '$host'." );
+ $this->errorConnection = $conn;
+ $conn = false;
+ }
+ }
+ }
+
+ if ( $conn instanceof IDatabase && !$conn->isOpen() ) {
+ // Connection was made but later unrecoverably lost for some reason.
+ // Do not return a handle that will just throw exceptions on use,
+ // but let the calling code (e.g. getReaderIndex) try another server.
+ // See DatabaseMyslBase::ping() for how this can happen.
+ $this->errorConnection = $conn;
+ $conn = false;
+ }
+
+ if ( $autoCommit && $conn instanceof IDatabase ) {
+ $conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
+ }
+
+ return $conn;
+ }
+
+ /**
+ * Open a connection to a foreign DB, or return one if it is already open.
+ *
+ * Increments a reference count on the returned connection which locks the
+ * connection to the requested domain. This reference count can be
+ * decremented by calling reuseConnection().
+ *
+ * If a connection is open to the appropriate server already, but with the wrong
+ * database, it will be switched to the right database and returned, as long as
+ * it has been freed first with reuseConnection().
+ *
+ * On error, returns false, and the connection which caused the
+ * error will be available via $this->errorConnection.
+ *
+ * @note If disable() was called on this LoadBalancer, this method will throw a DBAccessError.
+ *
+ * @param int $i Server index
+ * @param string $domain Domain ID to open
+ * @param int $flags Class CONN_* constant bitfield
+ * @return Database
+ */
+ private function openForeignConnection( $i, $domain, $flags = 0 ) {
+ $domainInstance = DatabaseDomain::newFromId( $domain );
+ $dbName = $domainInstance->getDatabase();
+ $prefix = $domainInstance->getTablePrefix();
+ $autoCommit = ( ( $flags & self::CONN_TRX_AUTO ) == self::CONN_TRX_AUTO );
+
+ if ( $autoCommit ) {
+ $connFreeKey = self::KEY_FOREIGN_FREE_NOROUND;
+ $connInUseKey = self::KEY_FOREIGN_INUSE_NOROUND;
+ } else {
+ $connFreeKey = self::KEY_FOREIGN_FREE;
+ $connInUseKey = self::KEY_FOREIGN_INUSE;
+ }
+
+ if ( isset( $this->mConns[$connInUseKey][$i][$domain] ) ) {
+ // Reuse an in-use connection for the same domain
+ $conn = $this->mConns[$connInUseKey][$i][$domain];
+ $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" );
+ } elseif ( isset( $this->mConns[$connFreeKey][$i][$domain] ) ) {
+ // Reuse a free connection for the same domain
+ $conn = $this->mConns[$connFreeKey][$i][$domain];
+ unset( $this->mConns[$connFreeKey][$i][$domain] );
+ $this->mConns[$connInUseKey][$i][$domain] = $conn;
+ $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" );
+ } elseif ( !empty( $this->mConns[$connFreeKey][$i] ) ) {
+ // Reuse a free connection from another domain
+ $conn = reset( $this->mConns[$connFreeKey][$i] );
+ $oldDomain = key( $this->mConns[$connFreeKey][$i] );
+ // The empty string as a DB name means "don't care".
+ // DatabaseMysqlBase::open() already handle this on connection.
+ if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) {
+ $this->mLastError = "Error selecting database '$dbName' on server " .
+ $conn->getServer() . " from client host {$this->host}";
+ $this->errorConnection = $conn;
+ $conn = false;
+ } else {
+ $conn->tablePrefix( $prefix );
+ unset( $this->mConns[$connFreeKey][$i][$oldDomain] );
+ $this->mConns[$connInUseKey][$i][$domain] = $conn;
+ $this->connLogger->debug( __METHOD__ .
+ ": reusing free connection from $oldDomain for $domain" );
+ }
+ } else {
+ if ( !isset( $this->mServers[$i] ) || !is_array( $this->mServers[$i] ) ) {
+ throw new InvalidArgumentException( "No server with index '$i'." );
+ }
+ // Open a new connection
+ $server = $this->mServers[$i];
+ $server['serverIndex'] = $i;
+ $server['foreignPoolRefCount'] = 0;
+ $server['foreign'] = true;
+ $server['autoCommitOnly'] = $autoCommit;
+ $conn = $this->reallyOpenConnection( $server, $dbName );
+ if ( !$conn->isOpen() ) {
+ $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" );
+ $this->errorConnection = $conn;
+ $conn = false;
+ } else {
+ $conn->tablePrefix( $prefix );
+ $this->mConns[$connInUseKey][$i][$domain] = $conn;
+ $this->connLogger->debug( __METHOD__ . ": opened new connection for $i/$domain" );
+ }
+ }
+
+ // Increment reference count
+ if ( $conn instanceof IDatabase ) {
+ $refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
+ $conn->setLBInfo( 'foreignPoolRefCount', $refCount + 1 );
+ }
+
+ return $conn;
+ }
+
+ /**
+ * Test if the specified index represents an open connection
+ *
+ * @param int $index Server index
+ * @access private
+ * @return bool
+ */
+ private function isOpen( $index ) {
+ if ( !is_integer( $index ) ) {
+ return false;
+ }
+
+ return (bool)$this->getAnyOpenConnection( $index );
+ }
+
+ /**
+ * Really opens a connection. Uncached.
+ * Returns a Database object whether or not the connection was successful.
+ * @access private
+ *
+ * @param array $server
+ * @param string|bool $dbNameOverride Use "" to not select any database
+ * @return Database
+ * @throws DBAccessError
+ * @throws InvalidArgumentException
+ */
+ protected function reallyOpenConnection( array $server, $dbNameOverride = false ) {
+ if ( $this->disabled ) {
+ throw new DBAccessError();
+ }
+
+ if ( $dbNameOverride !== false ) {
+ $server['dbname'] = $dbNameOverride;
+ }
+
+ // Let the handle know what the cluster master is (e.g. "db1052")
+ $masterName = $this->getServerName( $this->getWriterIndex() );
+ $server['clusterMasterHost'] = $masterName;
+
+ // Log when many connection are made on requests
+ if ( ++$this->connsOpened >= self::CONN_HELD_WARN_THRESHOLD ) {
+ $this->perfLogger->warning( __METHOD__ . ": " .
+ "{$this->connsOpened}+ connections made (master=$masterName)" );
+ }
+
+ $server['srvCache'] = $this->srvCache;
+ // Set loggers and profilers
+ $server['connLogger'] = $this->connLogger;
+ $server['queryLogger'] = $this->queryLogger;
+ $server['errorLogger'] = $this->errorLogger;
+ $server['profiler'] = $this->profiler;
+ $server['trxProfiler'] = $this->trxProfiler;
+ // Use the same agent and PHP mode for all DB handles
+ $server['cliMode'] = $this->cliMode;
+ $server['agent'] = $this->agent;
+ // Use DBO_DEFAULT flags by default for LoadBalancer managed databases. Assume that the
+ // application calls LoadBalancer::commitMasterChanges() before the PHP script completes.
+ $server['flags'] = isset( $server['flags'] ) ? $server['flags'] : IDatabase::DBO_DEFAULT;
+
+ // Create a live connection object
+ try {
+ $db = Database::factory( $server['type'], $server );
+ } catch ( DBConnectionError $e ) {
+ // FIXME: This is probably the ugliest thing I have ever done to
+ // PHP. I'm half-expecting it to segfault, just out of disgust. -- TS
+ $db = $e->db;
+ }
+
+ $db->setLBInfo( $server );
+ $db->setLazyMasterHandle(
+ $this->getLazyConnectionRef( self::DB_MASTER, [], $db->getDomainID() )
+ );
+ $db->setTableAliases( $this->tableAliases );
+
+ if ( $server['serverIndex'] === $this->getWriterIndex() ) {
+ if ( $this->trxRoundId !== false ) {
+ $this->applyTransactionRoundFlags( $db );
+ }
+ foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
+ $db->setTransactionListener( $name, $callback );
+ }
+ }
+
+ return $db;
+ }
+
+ /**
+ * @throws DBConnectionError
+ */
+ private function reportConnectionError() {
+ $conn = $this->errorConnection; // the connection which caused the error
+ $context = [
+ 'method' => __METHOD__,
+ 'last_error' => $this->mLastError,
+ ];
+
+ if ( $conn instanceof IDatabase ) {
+ $context['db_server'] = $conn->getServer();
+ $this->connLogger->warning(
+ "Connection error: {last_error} ({db_server})",
+ $context
+ );
+
+ // throws DBConnectionError
+ $conn->reportConnectionError( "{$this->mLastError} ({$context['db_server']})" );
+ } else {
+ // No last connection, probably due to all servers being too busy
+ $this->connLogger->error(
+ "LB failure with no last connection. Connection error: {last_error}",
+ $context
+ );
+
+ // If all servers were busy, mLastError will contain something sensible
+ throw new DBConnectionError( null, $this->mLastError );
+ }
+ }
+
+ public function getWriterIndex() {
+ return 0;
+ }
+
+ public function haveIndex( $i ) {
+ return array_key_exists( $i, $this->mServers );
+ }
+
+ public function isNonZeroLoad( $i ) {
+ return array_key_exists( $i, $this->mServers ) && $this->mLoads[$i] != 0;
+ }
+
+ public function getServerCount() {
+ return count( $this->mServers );
+ }
+
+ public function getServerName( $i ) {
+ if ( isset( $this->mServers[$i]['hostName'] ) ) {
+ $name = $this->mServers[$i]['hostName'];
+ } elseif ( isset( $this->mServers[$i]['host'] ) ) {
+ $name = $this->mServers[$i]['host'];
+ } else {
+ $name = '';
+ }
+
+ return ( $name != '' ) ? $name : 'localhost';
+ }
+
+ public function getServerType( $i ) {
+ return isset( $this->mServers[$i]['type'] ) ? $this->mServers[$i]['type'] : 'unknown';
+ }
+
+ /**
+ * @deprecated Since 1.30, no alternative
+ */
+ public function getServerInfo( $i ) {
+ wfDeprecated( __METHOD__, '1.30' );
+ if ( isset( $this->mServers[$i] ) ) {
+ return $this->mServers[$i];
+ } else {
+ return false;
+ }
+ }
+
+ /**
+ * @deprecated Since 1.30, construct new object
+ */
+ public function setServerInfo( $i, array $serverInfo ) {
+ wfDeprecated( __METHOD__, '1.30' );
+ $this->mServers[$i] = $serverInfo;
+ }
+
+ public function getMasterPos() {
+ # If this entire request was served from a replica DB without opening a connection to the
+ # master (however unlikely that may be), then we can fetch the position from the replica DB.
+ $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
+ if ( !$masterConn ) {
+ $serverCount = count( $this->mServers );
+ for ( $i = 1; $i < $serverCount; $i++ ) {
+ $conn = $this->getAnyOpenConnection( $i );
+ if ( $conn ) {
+ return $conn->getReplicaPos();
+ }
+ }
+ } else {
+ return $masterConn->getMasterPos();
+ }
+
+ return false;
+ }
+
+ public function disable() {
+ $this->closeAll();
+ $this->disabled = true;
+ }
+
+ public function closeAll() {
+ $this->forEachOpenConnection( function ( IDatabase $conn ) {
+ $host = $conn->getServer();
+ $this->connLogger->debug( "Closing connection to database '$host'." );
+ $conn->close();
+ } );
+
+ $this->mConns = [
+ self::KEY_LOCAL => [],
+ self::KEY_FOREIGN_INUSE => [],
+ self::KEY_FOREIGN_FREE => [],
+ self::KEY_LOCAL_NOROUND => [],
+ self::KEY_FOREIGN_INUSE_NOROUND => [],
+ self::KEY_FOREIGN_FREE_NOROUND => []
+ ];
+ $this->connsOpened = 0;
+ }
+
+ public function closeConnection( IDatabase $conn ) {
+ $serverIndex = $conn->getLBInfo( 'serverIndex' ); // second index level of mConns
+ foreach ( $this->mConns as $type => $connsByServer ) {
+ if ( !isset( $connsByServer[$serverIndex] ) ) {
+ continue;
+ }
+
+ foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) {
+ if ( $conn === $trackedConn ) {
+ $host = $this->getServerName( $i );
+ $this->connLogger->debug( "Closing connection to database $i at '$host'." );
+ unset( $this->mConns[$type][$serverIndex][$i] );
+ --$this->connsOpened;
+ break 2;
+ }
+ }
+ }
+
+ $conn->close();
+ }
+
+ public function commitAll( $fname = __METHOD__ ) {
+ $failures = [];
+
+ $restore = ( $this->trxRoundId !== false );
+ $this->trxRoundId = false;
+ $this->forEachOpenConnection(
+ function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
+ try {
+ $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
+ } catch ( DBError $e ) {
+ call_user_func( $this->errorLogger, $e );
+ $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
+ }
+ if ( $restore && $conn->getLBInfo( 'master' ) ) {
+ $this->undoTransactionRoundFlags( $conn );
+ }
+ }
+ );
+
+ if ( $failures ) {
+ throw new DBExpectedError(
+ null,
+ "Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
+ );
+ }
+ }
+
+ public function finalizeMasterChanges() {
+ $this->forEachOpenMasterConnection( function ( Database $conn ) {
+ // Any error should cause all DB transactions to be rolled back together
+ $conn->setTrxEndCallbackSuppression( false );
+ $conn->runOnTransactionPreCommitCallbacks();
+ // Defer post-commit callbacks until COMMIT finishes for all DBs
+ $conn->setTrxEndCallbackSuppression( true );
+ } );
+ }
+
+ public function approveMasterChanges( array $options ) {
+ $limit = isset( $options['maxWriteDuration'] ) ? $options['maxWriteDuration'] : 0;
+ $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $limit ) {
+ // If atomic sections or explicit transactions are still open, some caller must have
+ // caught an exception but failed to properly rollback any changes. Detect that and
+ // throw and error (causing rollback).
+ if ( $conn->explicitTrxActive() ) {
+ throw new DBTransactionError(
+ $conn,
+ "Explicit transaction still active. A caller may have caught an error."
+ );
+ }
+ // Assert that the time to replicate the transaction will be sane.
+ // If this fails, then all DB transactions will be rollback back together.
+ $time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
+ if ( $limit > 0 && $time > $limit ) {
+ throw new DBTransactionSizeError(
+ $conn,
+ "Transaction spent $time second(s) in writes, exceeding the limit of $limit.",
+ [ $time, $limit ]
+ );
+ }
+ // If a connection sits idle while slow queries execute on another, that connection
+ // may end up dropped before the commit round is reached. Ping servers to detect this.
+ if ( $conn->writesOrCallbacksPending() && !$conn->ping() ) {
+ throw new DBTransactionError(
+ $conn,
+ "A connection to the {$conn->getDBname()} database was lost before commit."
+ );
+ }
+ } );
+ }
+
+ public function beginMasterChanges( $fname = __METHOD__ ) {
+ if ( $this->trxRoundId !== false ) {
+ throw new DBTransactionError(
+ null,
+ "$fname: Transaction round '{$this->trxRoundId}' already started."
+ );
+ }
+ $this->trxRoundId = $fname;
+
+ $failures = [];
+ $this->forEachOpenMasterConnection(
+ function ( Database $conn ) use ( $fname, &$failures ) {
+ $conn->setTrxEndCallbackSuppression( true );
+ try {
+ $conn->flushSnapshot( $fname );
+ } catch ( DBError $e ) {
+ call_user_func( $this->errorLogger, $e );
+ $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
+ }
+ $conn->setTrxEndCallbackSuppression( false );
+ $this->applyTransactionRoundFlags( $conn );
+ }
+ );
+
+ if ( $failures ) {
+ throw new DBExpectedError(
+ null,
+ "$fname: Flush failed on server(s) " . implode( "\n", array_unique( $failures ) )
+ );
+ }
+ }
+
+ public function commitMasterChanges( $fname = __METHOD__ ) {
+ $failures = [];
+
+ /** @noinspection PhpUnusedLocalVariableInspection */
+ $scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
+
+ $restore = ( $this->trxRoundId !== false );
+ $this->trxRoundId = false;
+ $this->forEachOpenMasterConnection(
+ function ( IDatabase $conn ) use ( $fname, $restore, &$failures ) {
+ try {
+ if ( $conn->writesOrCallbacksPending() ) {
+ $conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
+ } elseif ( $restore ) {
+ $conn->flushSnapshot( $fname );
+ }
+ } catch ( DBError $e ) {
+ call_user_func( $this->errorLogger, $e );
+ $failures[] = "{$conn->getServer()}: {$e->getMessage()}";
+ }
+ if ( $restore ) {
+ $this->undoTransactionRoundFlags( $conn );
+ }
+ }
+ );
+
+ if ( $failures ) {
+ throw new DBExpectedError(
+ null,
+ "$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
+ );
+ }
+ }
+
+ public function runMasterPostTrxCallbacks( $type ) {
+ $e = null; // first exception
+ $this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
+ $conn->setTrxEndCallbackSuppression( false );
+ if ( $conn->writesOrCallbacksPending() ) {
+ // This happens if onTransactionIdle() callbacks leave callbacks on *another* DB
+ // (which finished its callbacks already). Warn and recover in this case. Let the
+ // callbacks run in the final commitMasterChanges() in LBFactory::shutdown().
+ $this->queryLogger->info( __METHOD__ . ": found writes/callbacks pending." );
+ return;
+ } elseif ( $conn->trxLevel() ) {
+ // This happens for single-DB setups where DB_REPLICA uses the master DB,
+ // thus leaving an implicit read-only transaction open at this point. It
+ // also happens if onTransactionIdle() callbacks leave implicit transactions
+ // open on *other* DBs (which is slightly improper). Let these COMMIT on the
+ // next call to commitMasterChanges(), possibly in LBFactory::shutdown().
+ return;
+ }
+ try {
+ $conn->runOnTransactionIdleCallbacks( $type );
+ } catch ( Exception $ex ) {
+ $e = $e ?: $ex;
+ }
+ try {
+ $conn->runTransactionListenerCallbacks( $type );
+ } catch ( Exception $ex ) {
+ $e = $e ?: $ex;
+ }
+ } );
+
+ return $e;
+ }
+
+ public function rollbackMasterChanges( $fname = __METHOD__ ) {
+ $restore = ( $this->trxRoundId !== false );
+ $this->trxRoundId = false;
+ $this->forEachOpenMasterConnection(
+ function ( IDatabase $conn ) use ( $fname, $restore ) {
+ if ( $conn->writesOrCallbacksPending() ) {
+ $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
+ }
+ if ( $restore ) {
+ $this->undoTransactionRoundFlags( $conn );
+ }
+ }
+ );
+ }
+
+ public function suppressTransactionEndCallbacks() {
+ $this->forEachOpenMasterConnection( function ( Database $conn ) {
+ $conn->setTrxEndCallbackSuppression( true );
+ } );
+ }
+
+ /**
+ * @param IDatabase $conn
+ */
+ private function applyTransactionRoundFlags( IDatabase $conn ) {
+ if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
+ return; // transaction rounds do not apply to these connections
+ }
+
+ if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
+ // DBO_TRX is controlled entirely by CLI mode presence with DBO_DEFAULT.
+ // Force DBO_TRX even in CLI mode since a commit round is expected soon.
+ $conn->setFlag( $conn::DBO_TRX, $conn::REMEMBER_PRIOR );
+ // If config has explicitly requested DBO_TRX be either on or off by not
+ // setting DBO_DEFAULT, then respect that. Forcing no transactions is useful
+ // for things like blob stores (ExternalStore) which want auto-commit mode.
+ }
+ }
+
+ /**
+ * @param IDatabase $conn
+ */
+ private function undoTransactionRoundFlags( IDatabase $conn ) {
+ if ( $conn->getLBInfo( 'autoCommitOnly' ) ) {
+ return; // transaction rounds do not apply to these connections
+ }
+
+ if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
+ $conn->restoreFlags( $conn::RESTORE_PRIOR );
+ }
+ }
+
+ public function flushReplicaSnapshots( $fname = __METHOD__ ) {
+ $this->forEachOpenReplicaConnection( function ( IDatabase $conn ) {
+ $conn->flushSnapshot( __METHOD__ );
+ } );
+ }
+
+ public function hasMasterConnection() {
+ return $this->isOpen( $this->getWriterIndex() );
+ }
+
+ public function hasMasterChanges() {
+ $pending = 0;
+ $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$pending ) {
+ $pending |= $conn->writesOrCallbacksPending();
+ } );
+
+ return (bool)$pending;
+ }
+
+ public function lastMasterChangeTimestamp() {
+ $lastTime = false;
+ $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$lastTime ) {
+ $lastTime = max( $lastTime, $conn->lastDoneWrites() );
+ } );
+
+ return $lastTime;
+ }
+
+ public function hasOrMadeRecentMasterChanges( $age = null ) {
+ $age = ( $age === null ) ? $this->mWaitTimeout : $age;
+
+ return ( $this->hasMasterChanges()
+ || $this->lastMasterChangeTimestamp() > microtime( true ) - $age );
+ }
+
+ public function pendingMasterChangeCallers() {
+ $fnames = [];
+ $this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( &$fnames ) {
+ $fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
+ } );
+
+ return $fnames;
+ }
+
+ public function getLaggedReplicaMode( $domain = false ) {
+ // No-op if there is only one DB (also avoids recursion)
+ if ( !$this->laggedReplicaMode && $this->getServerCount() > 1 ) {
+ try {
+ // See if laggedReplicaMode gets set
+ $conn = $this->getConnection( self::DB_REPLICA, false, $domain );
+ $this->reuseConnection( $conn );
+ } catch ( DBConnectionError $e ) {
+ // Avoid expensive re-connect attempts and failures
+ $this->allReplicasDownMode = true;
+ $this->laggedReplicaMode = true;
+ }
+ }
+
+ return $this->laggedReplicaMode;
+ }
+
+ /**
+ * @param bool $domain
+ * @return bool
+ * @deprecated 1.28; use getLaggedReplicaMode()
+ */
+ public function getLaggedSlaveMode( $domain = false ) {
+ return $this->getLaggedReplicaMode( $domain );
+ }
+
+ public function laggedReplicaUsed() {
+ return $this->laggedReplicaMode;
+ }
+
+ /**
+ * @return bool
+ * @since 1.27
+ * @deprecated Since 1.28; use laggedReplicaUsed()
+ */
+ public function laggedSlaveUsed() {
+ return $this->laggedReplicaUsed();
+ }
+
+ public function getReadOnlyReason( $domain = false, IDatabase $conn = null ) {
+ if ( $this->readOnlyReason !== false ) {
+ return $this->readOnlyReason;
+ } elseif ( $this->getLaggedReplicaMode( $domain ) ) {
+ if ( $this->allReplicasDownMode ) {
+ return 'The database has been automatically locked ' .
+ 'until the replica database servers become available';
+ } else {
+ return 'The database has been automatically locked ' .
+ 'while the replica database servers catch up to the master.';
+ }
+ } elseif ( $this->masterRunningReadOnly( $domain, $conn ) ) {
+ return 'The database master is running in read-only mode.';
+ }
+
+ return false;
+ }
+
+ /**
+ * @param string $domain Domain ID, or false for the current domain
+ * @param IDatabase|null $conn DB master connectionl used to avoid loops [optional]
+ * @return bool
+ */
+ private function masterRunningReadOnly( $domain, IDatabase $conn = null ) {
+ $cache = $this->wanCache;
+ $masterServer = $this->getServerName( $this->getWriterIndex() );
+
+ return (bool)$cache->getWithSetCallback(
+ $cache->makeGlobalKey( __CLASS__, 'server-read-only', $masterServer ),
+ self::TTL_CACHE_READONLY,
+ function () use ( $domain, $conn ) {
+ $old = $this->trxProfiler->setSilenced( true );
+ try {
+ $dbw = $conn ?: $this->getConnection( self::DB_MASTER, [], $domain );
+ $readOnly = (int)$dbw->serverIsReadOnly();
+ if ( !$conn ) {
+ $this->reuseConnection( $dbw );
+ }
+ } catch ( DBError $e ) {
+ $readOnly = 0;
+ }
+ $this->trxProfiler->setSilenced( $old );
+ return $readOnly;
+ },
+ [ 'pcTTL' => $cache::TTL_PROC_LONG, 'busyValue' => 0 ]
+ );
+ }
+
+ public function allowLagged( $mode = null ) {
+ if ( $mode === null ) {
+ return $this->mAllowLagged;
+ }
+ $this->mAllowLagged = $mode;
+
+ return $this->mAllowLagged;
+ }
+
+ public function pingAll() {
+ $success = true;
+ $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$success ) {
+ if ( !$conn->ping() ) {
+ $success = false;
+ }
+ } );
+
+ return $success;
+ }
+
+ public function forEachOpenConnection( $callback, array $params = [] ) {
+ foreach ( $this->mConns as $connsByServer ) {
+ foreach ( $connsByServer as $serverConns ) {
+ foreach ( $serverConns as $conn ) {
+ $mergedParams = array_merge( [ $conn ], $params );
+ call_user_func_array( $callback, $mergedParams );
+ }
+ }
+ }
+ }
+
+ public function forEachOpenMasterConnection( $callback, array $params = [] ) {
+ $masterIndex = $this->getWriterIndex();
+ foreach ( $this->mConns as $connsByServer ) {
+ if ( isset( $connsByServer[$masterIndex] ) ) {
+ /** @var IDatabase $conn */
+ foreach ( $connsByServer[$masterIndex] as $conn ) {
+ $mergedParams = array_merge( [ $conn ], $params );
+ call_user_func_array( $callback, $mergedParams );
+ }
+ }
+ }
+ }
+
+ public function forEachOpenReplicaConnection( $callback, array $params = [] ) {
+ foreach ( $this->mConns as $connsByServer ) {
+ foreach ( $connsByServer as $i => $serverConns ) {
+ if ( $i === $this->getWriterIndex() ) {
+ continue; // skip master
+ }
+ foreach ( $serverConns as $conn ) {
+ $mergedParams = array_merge( [ $conn ], $params );
+ call_user_func_array( $callback, $mergedParams );
+ }
+ }
+ }
+ }
+
+ public function getMaxLag( $domain = false ) {
+ $maxLag = -1;
+ $host = '';
+ $maxIndex = 0;
+
+ if ( $this->getServerCount() <= 1 ) {
+ return [ $host, $maxLag, $maxIndex ]; // no replication = no lag
+ }
+
+ $lagTimes = $this->getLagTimes( $domain );
+ foreach ( $lagTimes as $i => $lag ) {
+ if ( $this->mLoads[$i] > 0 && $lag > $maxLag ) {
+ $maxLag = $lag;
+ $host = $this->mServers[$i]['host'];
+ $maxIndex = $i;
+ }
+ }
+
+ return [ $host, $maxLag, $maxIndex ];
+ }
+
+ public function getLagTimes( $domain = false ) {
+ if ( $this->getServerCount() <= 1 ) {
+ return [ $this->getWriterIndex() => 0 ]; // no replication = no lag
+ }
+
+ $knownLagTimes = []; // map of (server index => 0 seconds)
+ $indexesWithLag = [];
+ foreach ( $this->mServers as $i => $server ) {
+ if ( empty( $server['is static'] ) ) {
+ $indexesWithLag[] = $i; // DB server might have replication lag
+ } else {
+ $knownLagTimes[$i] = 0; // DB server is a non-replicating and read-only archive
+ }
+ }
+
+ return $this->getLoadMonitor()->getLagTimes( $indexesWithLag, $domain ) + $knownLagTimes;
+ }
+
+ public function safeGetLag( IDatabase $conn ) {
+ if ( $this->getServerCount() <= 1 ) {
+ return 0;
+ } else {
+ return $conn->getLag();
+ }
+ }
+
+ /**
+ * @param IDatabase $conn
+ * @param DBMasterPos|bool $pos
+ * @param int $timeout
+ * @return bool
+ */
+ public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = 10 ) {
+ if ( $this->getServerCount() <= 1 || !$conn->getLBInfo( 'replica' ) ) {
+ return true; // server is not a replica DB
+ }
+
+ if ( !$pos ) {
+ // Get the current master position, opening a connection if needed
+ $masterConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
+ if ( $masterConn ) {
+ $pos = $masterConn->getMasterPos();
+ } else {
+ $masterConn = $this->openConnection( $this->getWriterIndex(), self::DOMAIN_ANY );
+ $pos = $masterConn->getMasterPos();
+ $this->closeConnection( $masterConn );
+ }
+ }
+
+ if ( $pos instanceof DBMasterPos ) {
+ $result = $conn->masterPosWait( $pos, $timeout );
+ if ( $result == -1 || is_null( $result ) ) {
+ $msg = __METHOD__ . ": Timed out waiting on {$conn->getServer()} pos {$pos}";
+ $this->replLogger->warning( "$msg" );
+ $ok = false;
+ } else {
+ $this->replLogger->info( __METHOD__ . ": Done" );
+ $ok = true;
+ }
+ } else {
+ $ok = false; // something is misconfigured
+ $this->replLogger->error( "Could not get master pos for {$conn->getServer()}." );
+ }
+
+ return $ok;
+ }
+
+ public function setTransactionListener( $name, callable $callback = null ) {
+ if ( $callback ) {
+ $this->trxRecurringCallbacks[$name] = $callback;
+ } else {
+ unset( $this->trxRecurringCallbacks[$name] );
+ }
+ $this->forEachOpenMasterConnection(
+ function ( IDatabase $conn ) use ( $name, $callback ) {
+ $conn->setTransactionListener( $name, $callback );
+ }
+ );
+ }
+
+ public function setTableAliases( array $aliases ) {
+ $this->tableAliases = $aliases;
+ }
+
+ public function setDomainPrefix( $prefix ) {
+ // Find connections to explicit foreign domains still marked as in-use...
+ $domainsInUse = [];
+ $this->forEachOpenConnection( function ( IDatabase $conn ) use ( &$domainsInUse ) {
+ // Once reuseConnection() is called on a handle, its reference count goes from 1 to 0.
+ // Until then, it is still in use by the caller (explicitly or via DBConnRef scope).
+ if ( $conn->getLBInfo( 'foreignPoolRefCount' ) > 0 ) {
+ $domainsInUse[] = $conn->getDomainID();
+ }
+ } );
+
+ // Do not switch connections to explicit foreign domains unless marked as safe
+ if ( $domainsInUse ) {
+ $domains = implode( ', ', $domainsInUse );
+ throw new DBUnexpectedError( null,
+ "Foreign domain connections are still in use ($domains)." );
+ }
+
+ $this->localDomain = new DatabaseDomain(
+ $this->localDomain->getDatabase(),
+ null,
+ $prefix
+ );
+
+ $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
+ $db->tablePrefix( $prefix );
+ } );
+ }
+
+ /**
+ * Make PHP ignore user aborts/disconnects until the returned
+ * value leaves scope. This returns null and does nothing in CLI mode.
+ *
+ * @return ScopedCallback|null
+ */
+ final protected function getScopedPHPBehaviorForCommit() {
+ if ( PHP_SAPI != 'cli' ) { // https://bugs.php.net/bug.php?id=47540
+ $old = ignore_user_abort( true ); // avoid half-finished operations
+ return new ScopedCallback( function () use ( $old ) {
+ ignore_user_abort( $old );
+ } );
+ }
+
+ return null;
+ }
+
+ function __destruct() {
+ // Avoid connection leaks for sanity
+ $this->disable();
+ }
+}
+
+class_alias( LoadBalancer::class, 'LoadBalancer' );
scripts.mit.edu / autoinstallsdev / mediawiki.git / blobdiff