diff options
Diffstat (limited to 'www/wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php')
| -rw-r--r-- | www/wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php | 1864 |
1 files changed, 1864 insertions, 0 deletions
diff --git a/www/wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php b/www/wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php new file mode 100644 index 00000000..d5e65cdd --- /dev/null +++ b/www/wiki/includes/libs/rdbms/loadbalancer/LoadBalancer.php @@ -0,0 +1,1864 @@ +<?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 + */ +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 $servers; + /** @var Database[][][] Map of (connection category => server index => IDatabase[]) */ + private $conns; + /** @var float[] Map of (server index => weight) */ + private $loads; + /** @var array[] Map of (group => server index => weight) */ + private $groupLoads; + /** @var bool Whether to disregard replica DB lag as a factor in replica DB selection */ + private $allowLagged; + /** @var int Seconds to spend waiting on replica DB lag to resolve */ + private $waitTimeout; + /** @var array The LoadMonitor configuration */ + private $loadMonitorConfig; + /** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */ + private $tableAliases = []; + /** @var string[] Map of (index alias => index) */ + private $indexAliases = []; + + /** @var ILoadMonitor */ + private $loadMonitor; + /** @var callable|null Callback to run before the first connection attempt */ + private $chronologyCallback; + /** @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 $readIndex; + /** @var bool|DBMasterPos False if not set */ + private $waitForPos; + /** @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 $lastError = '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 callable Deprecation logger */ + private $deprecationLogger; + + /** @var bool */ + private $disabled = false; + /** @var bool Whether any connection has been attempted yet */ + private $connectionAttempted = false; + /** @var int */ + private $maxLag = self::MAX_LAG_DEFAULT; + + /** @var int Warn when this many connection are held */ + const CONN_HELD_WARN_THRESHOLD = 10; + + /** @var int Default 'maxLag' when unspecified */ + const MAX_LAG_DEFAULT = 10; + /** @var int Default 'waitTimeout' when unspecified */ + const MAX_WAIT_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->servers = $params['servers']; + foreach ( $this->servers as $i => $server ) { + if ( $i == 0 ) { + $this->servers[$i]['master'] = true; + } else { + $this->servers[$i]['replica'] = true; + } + } + + $localDomain = isset( $params['localDomain'] ) + ? DatabaseDomain::newFromId( $params['localDomain'] ) + : DatabaseDomain::newUnspecified(); + $this->setLocalDomain( $localDomain ); + + $this->waitTimeout = isset( $params['waitTimeout'] ) + ? $params['waitTimeout'] + : self::MAX_WAIT_DEFAULT; + + $this->readIndex = -1; + $this->conns = [ + // 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->loads = []; + $this->waitForPos = false; + $this->allowLagged = false; + + if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) { + $this->readOnlyReason = $params['readOnlyReason']; + } + + if ( isset( $params['maxLag'] ) ) { + $this->maxLag = $params['maxLag']; + } + + if ( isset( $params['loadMonitor'] ) ) { + $this->loadMonitorConfig = $params['loadMonitor']; + } else { + $this->loadMonitorConfig = [ 'class' => 'LoadMonitorNull' ]; + } + $this->loadMonitorConfig += [ 'lagWarnThreshold' => $this->maxLag ]; + + foreach ( $params['servers'] as $i => $server ) { + $this->loads[$i] = $server['load']; + if ( isset( $server['groupLoads'] ) ) { + foreach ( $server['groupLoads'] as $group => $ratio ) { + if ( !isset( $this->groupLoads[$group] ) ) { + $this->groupLoads[$group] = []; + } + $this->groupLoads[$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 ); + }; + $this->deprecationLogger = isset( $params['deprecationLogger'] ) + ? $params['deprecationLogger'] + : function ( $msg ) { + trigger_error( $msg, E_USER_DEPRECATED ); + }; + + 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' || PHP_SAPI === 'phpdbg' ); + $this->agent = isset( $params['agent'] ) ? $params['agent'] : ''; + + if ( isset( $params['chronologyCallback'] ) ) { + $this->chronologyCallback = $params['chronologyCallback']; + } + } + + /** + * Get the local (and default) database domain ID of connection handles + * + * @see DatabaseDomain + * @return string Database domain ID; this specifies DB name, schema, and table prefix + * @since 1.31 + */ + public function getLocalDomainID() { + return $this->localDomain->getId(); + } + + /** + * 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( $this->servers[$i]['max lag'] ) + ? $this->servers[$i]['max lag'] + : $this->maxLag; // default + # Constrain that futher by $maxLag argument + $maxServerLag = min( $maxServerLag, $maxLag ); + + $host = $this->getServerName( $i ); + if ( $lag === false && !is_infinite( $maxServerLag ) ) { + $this->replLogger->error( + __METHOD__ . + ": 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->servers ) == 1 ) { + // Skip the load balancing if there's only one server + return $this->getWriterIndex(); + } elseif ( $group === false && $this->readIndex >= 0 ) { + // Shortcut if the generic reader index was already cached + return $this->readIndex; + } + + if ( $group !== false ) { + // Use the server weight array for this load group + if ( isset( $this->groupLoads[$group] ) ) { + $loads = $this->groupLoads[$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->loads; + } + + // 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 "waitForPos" + list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain ); + if ( $i === false ) { + // Replica DB connection unsuccessful + return false; + } + + if ( $this->waitForPos && $i != $this->getWriterIndex() ) { + // Before any data queries are run, wait for the server to catch up to the + // specified position. This is used to improve session consistency. Note that + // when LoadBalancer::waitFor() sets "waitForPos", the waiting triggers here, + // so update laggedReplicaMode as needed for consistency. + if ( !$this->doWait( $i ) ) { + $laggedReplicaMode = true; + } + } + + if ( $this->readIndex <= 0 && $this->loads[$i] > 0 && $group === false ) { + // Cache the generic reader index for future ungrouped DB_REPLICA handles + $this->readIndex = $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->allowLagged || $laggedReplicaMode ) { + $i = ArrayUtils::pickRandom( $currentLoads ); + } else { + $i = false; + if ( $this->waitForPos && $this->waitForPos->asOfTime() ) { + // "chronologyCallback" sets "waitForPos" 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->waitForPos->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( + __METHOD__ . ": 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( __METHOD__ . ": all servers down" ); + } + + return [ $i, $laggedReplicaMode ]; + } + + public function waitFor( $pos ) { + $oldPos = $this->waitForPos; + try { + $this->waitForPos = $pos; + // If a generic reader connection was already established, then wait now + $i = $this->readIndex; + 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->waitForPos; + try { + $this->waitForPos = $pos; + + $i = $this->readIndex; + if ( $i <= 0 ) { + // Pick a generic replica DB if there isn't one yet + $readLoads = $this->loads; + 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->waitForPos = $oldPos; + } + + return $ok; + } + + public function waitForAll( $pos, $timeout = null ) { + $timeout = $timeout ?: $this->waitTimeout; + + $oldPos = $this->waitForPos; + try { + $this->waitForPos = $pos; + $serverCount = count( $this->servers ); + + $ok = true; + for ( $i = 1; $i < $serverCount; $i++ ) { + if ( $this->loads[$i] > 0 ) { + $start = microtime( true ); + $ok = $this->doWait( $i, true, $timeout ) && $ok; + $timeout -= intval( microtime( true ) - $start ); + if ( $timeout <= 0 ) { + break; // timeout reached + } + } + } + } finally { + # Restore the old position, as this is not used for lag-protection but for throttling + $this->waitForPos = $oldPos; + } + + return $ok; + } + + /** + * @param DBMasterPos|bool $pos + */ + private function setWaitForPositionIfHigher( $pos ) { + if ( !$pos ) { + return; + } + + if ( !$this->waitForPos || $pos->hasReached( $this->waitForPos ) ) { + $this->waitForPos = $pos; + } + } + + public function getAnyOpenConnection( $i, $flags = 0 ) { + $autocommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT ); + foreach ( $this->conns as $connsByServer ) { + if ( !isset( $connsByServer[$i] ) ) { + continue; + } + + foreach ( $connsByServer[$i] as $conn ) { + if ( !$autocommit || $conn->getLBInfo( 'autoCommitOnly' ) ) { + return $conn; + } + } + } + + 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 "waitTimeout" given to __construct() + * @return bool + */ + protected function doWait( $index, $open = false, $timeout = null ) { + $timeout = max( 1, intval( $timeout ?: $this->waitTimeout ) ); + + // 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->waitForPos ) + ) { + $this->replLogger->debug( + __METHOD__ . + ': replica DB {dbserver} known to be caught up (pos >= $knownReachedPos).', + [ 'dbserver' => $server ] + ); + return true; + } + + // Find a connection to wait on, creating one if needed and allowed + $close = false; // close the connection afterwards + $conn = $this->getAnyOpenConnection( $index ); + if ( !$conn ) { + if ( !$open ) { + $this->replLogger->debug( + __METHOD__ . ': no connection open for {dbserver}', + [ 'dbserver' => $server ] + ); + + return false; + } else { + $conn = $this->openConnection( $index, self::DOMAIN_ANY ); + if ( !$conn ) { + $this->replLogger->warning( + __METHOD__ . ': failed to connect to {dbserver}', + [ 'dbserver' => $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 {dbserver} to catch up...', + [ 'dbserver' => $server ] + ); + + $result = $conn->masterPosWait( $this->waitForPos, $timeout ); + + if ( $result === null ) { + $this->replLogger->warning( + __METHOD__ . ': Errored out waiting on {host} pos {pos}', + [ + 'host' => $server, + 'pos' => $this->waitForPos, + 'trace' => ( new RuntimeException() )->getTraceAsString() + ] + ); + $ok = false; + } elseif ( $result == -1 ) { + $this->replLogger->warning( + __METHOD__ . ': Timed out waiting on {host} pos {pos}', + [ + 'host' => $server, + 'pos' => $this->waitForPos, + 'trace' => ( new RuntimeException() )->getTraceAsString() + ] + ); + $ok = false; + } else { + $this->replLogger->debug( __METHOD__ . ": done waiting" ); + $ok = true; + // Remember that the DB reached this point + $this->srvCache->set( $key, $this->waitForPos, 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 + } + + if ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) === self::CONN_TRX_AUTOCOMMIT ) { + // Assuming all servers are of the same type (or similar), which is overwhelmingly + // the case, use the master server information to get the attributes. The information + // for $i cannot be used since it might be DB_REPLICA, which might require connection + // attempts in order to be resolved into a real server index. + $attributes = $this->getServerAttributes( $this->getWriterIndex() ); + if ( $attributes[Database::ATTR_DB_LEVEL_LOCKING] ) { + // Callers sometimes want to (a) escape REPEATABLE-READ stateness without locking + // rows (e.g. FOR UPDATE) or (b) make small commits during a larger transactions + // to reduce lock contention. None of these apply for sqlite and using separate + // connections just causes self-deadlocks. + $flags &= ~self::CONN_TRX_AUTOCOMMIT; + $this->connLogger->info( __METHOD__ . + ': ignoring CONN_TRX_AUTOCOMMIT to avoid deadlocks.' ); + } + } + + $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(); + } elseif ( $i == self::DB_REPLICA ) { + # 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->lastError = '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->lastError = 'No working replica DB server: ' . $this->lastError; + // 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( IDatabase $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( $this->conns[$connInUseKey][$serverIndex][$domain] ) ) { + throw new InvalidArgumentException( __METHOD__ . + ": connection $serverIndex/$domain not found; it may have already been freed." ); + } elseif ( $this->conns[$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 ) { + $this->conns[$connFreeKey][$serverIndex][$domain] = $conn; + unset( $this->conns[$connInUseKey][$serverIndex][$domain] ); + if ( !$this->conns[$connInUseKey][$serverIndex] ) { + unset( $this->conns[$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->connectionAttempted && $this->chronologyCallback ) { + $this->connLogger->debug( __METHOD__ . ': calling initLB() before first connection.' ); + // Load any "waitFor" positions before connecting so that doWait() is triggered + $this->connectionAttempted = true; + call_user_func( $this->chronologyCallback, $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_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT ); + + 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( $this->conns[$connKey][$i][0] ) ) { + $conn = $this->conns[$connKey][$i][0]; + } else { + if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) { + throw new InvalidArgumentException( "No server with index '$i'." ); + } + // Open a new connection + $server = $this->servers[$i]; + $server['serverIndex'] = $i; + $server['autoCommitOnly'] = $autoCommit; + if ( $this->localDomain->getDatabase() !== null ) { + // Use the local domain table prefix if the local domain is specified + $server['tablePrefix'] = $this->localDomain->getTablePrefix(); + } + $conn = $this->reallyOpenConnection( $server, $this->localDomain ); + $host = $this->getServerName( $i ); + if ( $conn->isOpen() ) { + $this->connLogger->debug( + __METHOD__ . ": connected to database $i at '$host'." ); + $this->conns[$connKey][$i][0] = $conn; + } else { + $this->connLogger->warning( + __METHOD__ . ": 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_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT ); + + 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( $this->conns[$connInUseKey][$i][$domain] ) ) { + // Reuse an in-use connection for the same domain + $conn = $this->conns[$connInUseKey][$i][$domain]; + $this->connLogger->debug( __METHOD__ . ": reusing connection $i/$domain" ); + } elseif ( isset( $this->conns[$connFreeKey][$i][$domain] ) ) { + // Reuse a free connection for the same domain + $conn = $this->conns[$connFreeKey][$i][$domain]; + unset( $this->conns[$connFreeKey][$i][$domain] ); + $this->conns[$connInUseKey][$i][$domain] = $conn; + $this->connLogger->debug( __METHOD__ . ": reusing free connection $i/$domain" ); + } elseif ( !empty( $this->conns[$connFreeKey][$i] ) ) { + // Reuse a free connection from another domain + $conn = reset( $this->conns[$connFreeKey][$i] ); + $oldDomain = key( $this->conns[$connFreeKey][$i] ); + if ( strlen( $dbName ) && !$conn->selectDB( $dbName ) ) { + $this->lastError = "Error selecting database '$dbName' on server " . + $conn->getServer() . " from client host {$this->host}"; + $this->errorConnection = $conn; + $conn = false; + } else { + $conn->tablePrefix( $prefix ); + unset( $this->conns[$connFreeKey][$i][$oldDomain] ); + // Note that if $domain is an empty string, getDomainID() might not match it + $this->conns[$connInUseKey][$i][$conn->getDomainId()] = $conn; + $this->connLogger->debug( __METHOD__ . + ": reusing free connection from $oldDomain for $domain" ); + } + } else { + if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) { + throw new InvalidArgumentException( "No server with index '$i'." ); + } + // Open a new connection + $server = $this->servers[$i]; + $server['serverIndex'] = $i; + $server['foreignPoolRefCount'] = 0; + $server['foreign'] = true; + $server['autoCommitOnly'] = $autoCommit; + $conn = $this->reallyOpenConnection( $server, $domainInstance ); + if ( !$conn->isOpen() ) { + $this->connLogger->warning( __METHOD__ . ": connection error for $i/$domain" ); + $this->errorConnection = $conn; + $conn = false; + } else { + $conn->tablePrefix( $prefix ); // as specified + // Note that if $domain is an empty string, getDomainID() might not match it + $this->conns[$connInUseKey][$i][$conn->getDomainID()] = $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; + } + + public function getServerAttributes( $i ) { + return Database::attributesFromType( + $this->getServerType( $i ), + isset( $this->servers[$i]['driver'] ) ? $this->servers[$i]['driver'] : null + ); + } + + /** + * Test if the specified index represents an open connection + * + * @param int $index Server index + * @access private + * @return bool + */ + private function isOpen( $index ) { + if ( !is_int( $index ) ) { + return false; + } + + return (bool)$this->getAnyOpenConnection( $index ); + } + + /** + * Open a new network connection to a server (uncached) + * + * Returns a Database object whether or not the connection was successful. + * + * @param array $server + * @param DatabaseDomain $domainOverride Use an unspecified domain to not select any database + * @return Database + * @throws DBAccessError + * @throws InvalidArgumentException + */ + protected function reallyOpenConnection( array $server, DatabaseDomain $domainOverride ) { + if ( $this->disabled ) { + throw new DBAccessError(); + } + + // Handle $domainOverride being a specified or an unspecified domain + if ( $domainOverride->getDatabase() === null ) { + // Normally, an RDBMS requires a DB name specified on connection and the $server + // configuration array is assumed to already specify an appropriate DB name. + if ( $server['type'] === 'mysql' ) { + // For MySQL, DATABASE and SCHEMA are synonyms, connections need not specify a DB, + // and the DB name in $server might not exist due to legacy reasons (the default + // domain used to ignore the local LB domain, even when mismatched). + $server['dbname'] = null; + } + } else { + $server['dbname'] = $domainOverride->getDatabase(); + $server['schema'] = $domainOverride->getSchema(); + } + + // 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['deprecationLogger'] = $this->deprecationLogger; + $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 ); + $db->setIndexAliases( $this->indexAliases ); + + 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->lastError, + ]; + + if ( $conn instanceof IDatabase ) { + $context['db_server'] = $conn->getServer(); + $this->connLogger->warning( + __METHOD__ . ": connection error: {last_error} ({db_server})", + $context + ); + + // throws DBConnectionError + $conn->reportConnectionError( "{$this->lastError} ({$context['db_server']})" ); + } else { + // No last connection, probably due to all servers being too busy + $this->connLogger->error( + __METHOD__ . + ": LB failure with no last connection. Connection error: {last_error}", + $context + ); + + // If all servers were busy, "lastError" will contain something sensible + throw new DBConnectionError( null, $this->lastError ); + } + } + + public function getWriterIndex() { + return 0; + } + + public function haveIndex( $i ) { + return array_key_exists( $i, $this->servers ); + } + + public function isNonZeroLoad( $i ) { + return array_key_exists( $i, $this->servers ) && $this->loads[$i] != 0; + } + + public function getServerCount() { + return count( $this->servers ); + } + + public function getServerName( $i ) { + if ( isset( $this->servers[$i]['hostName'] ) ) { + $name = $this->servers[$i]['hostName']; + } elseif ( isset( $this->servers[$i]['host'] ) ) { + $name = $this->servers[$i]['host']; + } else { + $name = ''; + } + + return ( $name != '' ) ? $name : 'localhost'; + } + + public function getServerInfo( $i ) { + if ( isset( $this->servers[$i] ) ) { + return $this->servers[$i]; + } else { + return false; + } + } + + public function getServerType( $i ) { + return isset( $this->servers[$i]['type'] ) ? $this->servers[$i]['type'] : 'unknown'; + } + + 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->servers ); + 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(); + $this->connLogger->debug( + __METHOD__ . ": closing connection to database '$host'." ); + $conn->close(); + } ); + + $this->conns = [ + 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' ); + foreach ( $this->conns as $type => $connsByServer ) { + if ( !isset( $connsByServer[$serverIndex] ) ) { + continue; + } + + foreach ( $connsByServer[$serverIndex] as $i => $trackedConn ) { + if ( $conn === $trackedConn ) { + $host = $this->getServerName( $i ); + $this->connLogger->debug( + __METHOD__ . ": closing connection to database $i at '$host'." ); + unset( $this->conns[$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 ); + // Callbacks run in AUTO-COMMIT mode, so make sure no transactions are pending... + if ( $conn->writesPending() ) { + // This happens if onTransactionIdle() callbacks write to *other* handles + // (which already finished their callbacks). Let any callbacks run in the final + // commitMasterChanges() in LBFactory::shutdown(), when the transaction is gone. + $this->queryLogger->warning( __METHOD__ . ": found writes 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 ) { + $conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS ); + if ( $restore ) { + $this->undoTransactionRoundFlags( $conn ); + } + } + ); + } + + public function suppressTransactionEndCallbacks() { + $this->forEachOpenMasterConnection( function ( Database $conn ) { + $conn->setTrxEndCallbackSuppression( true ); + } ); + } + + /** + * Make all DB servers with DBO_DEFAULT/DBO_TRX set join the transaction round + * + * Some servers may have neither flag enabled, meaning that they opt out of such + * transaction rounds and remain in auto-commit mode. Such behavior might be desired + * when a DB server is used for something like simple key/value storage. + * + * @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 ( $conn->getFlag( $conn::DBO_TRX ) ) { + $conn->setLBInfo( 'trxRoundId', $this->trxRoundId ); + } + } + + /** + * @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_TRX ) ) { + $conn->setLBInfo( 'trxRoundId', false ); + } + + 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->waitTimeout : $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->allowLagged; + } + $this->allowLagged = $mode; + + return $this->allowLagged; + } + + 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->conns 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->conns 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->conns 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 ( $this->loads[$i] > 0 && $lag > $maxLag ) { + $maxLag = $lag; + $host = $this->servers[$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->servers 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|null $timeout + * @return bool + */ + public function safeWaitForMasterPos( IDatabase $conn, $pos = false, $timeout = null ) { + $timeout = max( 1, $timeout ?: $this->waitTimeout ); + + 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 {host} pos {pos}'; + $this->replLogger->warning( $msg, [ + 'host' => $conn->getServer(), + 'pos' => $pos, + 'trace' => ( new RuntimeException() )->getTraceAsString() + ] ); + $ok = false; + } else { + $this->replLogger->debug( __METHOD__ . ': done waiting' ); + $ok = true; + } + } else { + $ok = false; // something is misconfigured + $this->replLogger->error( + __METHOD__ . ': could not get master pos for {host}', + [ + 'host' => $conn->getServer(), + 'trace' => ( new RuntimeException() )->getTraceAsString() + ] + ); + } + + 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 setIndexAliases( array $aliases ) { + $this->indexAliases = $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)." ); + } + + $oldDomain = $this->localDomain->getId(); + $this->setLocalDomain( new DatabaseDomain( + $this->localDomain->getDatabase(), + $this->localDomain->getSchema(), + $prefix + ) ); + + $this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix, $oldDomain ) { + if ( !$db->getLBInfo( 'foreign' ) ) { + $db->tablePrefix( $prefix ); + } + } ); + } + + /** + * @param DatabaseDomain $domain + */ + private function setLocalDomain( DatabaseDomain $domain ) { + $this->localDomain = $domain; + // 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(); + } + } + + /** + * 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' ); |