<?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 ArrayUtils;
use BagOStuff;
use EmptyBagOStuff;
use InvalidArgumentException;
use LogicException;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use RuntimeException;
use Throwable;
use UnexpectedValueException;
use WANObjectCache;
use Wikimedia\RequestTimeout\CriticalSectionProvider;
use Wikimedia\ScopedCallback;
/**
* Database connection, tracking, load balancing, and transaction manager for a cluster
*
* @ingroup Database
*/
class LoadBalancer implements ILoadBalancer {
/** @var ILoadMonitor */
private $loadMonitor;
/** @var CriticalSectionProvider|null */
private $csProvider;
/** @var callable|null Callback to run before the first connection attempt */
private $chronologyCallback;
/** @var BagOStuff */
private $srvCache;
/** @var WANObjectCache */
private $wanCache;
/**
* @var callable|null An optional callback that returns a ScopedCallback instance,
* meant to profile the actual query execution in {@see Database::doQuery}
*/
private $profiler;
/** @var TransactionProfiler */
private $trxProfiler;
/** @var LoggerInterface */
private $connLogger;
/** @var LoggerInterface */
private $queryLogger;
/** @var LoggerInterface */
private $replLogger;
/** @var LoggerInterface */
private $perfLogger;
/** @var callable Exception logger */
private $errorLogger;
/** @var callable Deprecation logger */
private $deprecationLogger;
/** @var DatabaseDomain Local DB domain ID and default for selectDB() calls */
private $localDomain;
/** @var IDatabase[][][] Map of (pool category => server index => domain => IDatabase) */
private $conns;
/** @var string|null The name of the DB cluster */
private $clusterName;
/** @var array[] Map of (server index => server config array) */
private $servers;
/** @var array[] Map of (group => server index => weight) */
private $groupLoads;
/** @var int Seconds to spend waiting on replica DB lag to resolve */
private $waitTimeout;
/** @var array The LoadMonitor configuration */
private $loadMonitorConfig;
/** @var int */
private $maxLag;
/** @var string|null Default query group to use with getConnection() */
private $defaultGroup;
/** @var bool Whether this PHP instance is for a CLI script */
private $cliMode;
/** @var string Agent name for query profiling */
private $agent;
/** @var array[] $aliases Map of (table => (dbname, schema, prefix) map) */
private $tableAliases = [];
/** @var string[] Map of (index alias => index) */
private $indexAliases = [];
/** @var DatabaseDomain[]|string[] Map of (domain alias => DB domain) */
private $domainAliases = [];
/** @var callable[] Map of (name => callable) */
private $trxRecurringCallbacks = [];
/** @var bool[] Map of (domain => whether to use "temp tables only" mode) */
private $tempTablesOnlyMode = [];
/** @var string|bool Explicit DBO_TRX transaction round active or false if none */
private $trxRoundId = false;
/** @var string Stage of the current transaction round in the transaction round life-cycle */
private $trxRoundStage = self::ROUND_CURSORY;
/** @var Database Connection handle that caused a problem */
private $errorConnection;
/** @var int[] The group replica server indexes keyed by group */
private $readIndexByGroup = [];
/** @var bool|DBPrimaryPos Replication sync position or false if not set */
private $waitForPos;
/** @var bool Whether the generic reader fell back to a lagged replica DB */
private $laggedReplicaMode = false;
/** @var string The last DB selection or connection error */
private $lastError = 'Unknown error';
/** @var string|bool Reason this instance is read-only or false if not */
private $readOnlyReason = false;
/** @var int Total number of new connections ever made with this instance */
private $connectionCounter = 0;
/** @var bool */
private $disabled = false;
/** @var bool Whether the session consistency callback already executed */
private $chronologyCallbackTriggered = false;
/** var int An identifier for this class instance */
private $id;
/** @var int|null Integer ID of the managing LBFactory instance or null if none */
private $ownerId;
/** @var DatabaseDomain[] Map of (domain ID => domain instance) */
private $nonLocalDomainCache = [];
private const INFO_SERVER_INDEX = 'serverIndex';
private const INFO_AUTOCOMMIT_ONLY = 'autoCommitOnly';
private const INFO_FORIEGN = 'foreign';
private const INFO_FOREIGN_REF_COUNT = 'foreignPoolRefCount';
/**
* Default 'maxLag' when unspecified
* @internal Only for use within LoadBalancer/LoadMonitor
*/
public const MAX_LAG_DEFAULT = 6;
/** Warn when this many connection are held */
private const CONN_HELD_WARN_THRESHOLD = 10;
/** Default 'waitTimeout' when unspecified */
private const MAX_WAIT_DEFAULT = 10;
/** Seconds to cache primary DB server read-only status */
private const TTL_CACHE_READONLY = 5;
private const KEY_LOCAL = 'local';
private const KEY_FOREIGN_FREE = 'foreignFree';
private const KEY_FOREIGN_INUSE = 'foreignInUse';
private const KEY_LOCAL_NOROUND = 'localAutoCommit';
private const KEY_FOREIGN_FREE_NOROUND = 'foreignFreeAutoCommit';
private const KEY_FOREIGN_INUSE_NOROUND = 'foreignInUseAutoCommit';
private const KEY_LOCAL_DOMAIN = '__local__';
/** Transaction round, explicit or implicit, has not finished writing */
private const ROUND_CURSORY = 'cursory';
/** Transaction round writes are complete and ready for pre-commit checks */
private const ROUND_FINALIZED = 'finalized';
/** Transaction round passed final pre-commit checks */
private const ROUND_APPROVED = 'approved';
/** Transaction round was committed and post-commit callbacks must be run */
private const ROUND_COMMIT_CALLBACKS = 'commit-callbacks';
/** Transaction round was rolled back and post-rollback callbacks must be run */
private const ROUND_ROLLBACK_CALLBACKS = 'rollback-callbacks';
/** Transaction round encountered an error */
private const ROUND_ERROR = 'error';
/** @var int Idiom for getExistingReaderIndex() meaning "no index selected" */
private const READER_INDEX_NONE = -1;
public function __construct( array $params ) {
if ( !isset( $params['servers'] ) || !count( $params['servers'] ) ) {
throw new InvalidArgumentException( 'Missing or empty "servers" parameter' );
}
$localDomain = isset( $params['localDomain'] )
? DatabaseDomain::newFromId( $params['localDomain'] )
: DatabaseDomain::newUnspecified();
$this->setLocalDomain( $localDomain );
$this->maxLag = $params['maxLag'] ?? self::MAX_LAG_DEFAULT;
$listKey = -1;
$this->servers = [];
$this->groupLoads = [ self::GROUP_GENERIC => [] ];
foreach ( $params['servers'] as $i => $server ) {
if ( ++$listKey !== $i ) {
throw new UnexpectedValueException( 'List expected for "servers" parameter' );
}
$this->servers[$i] = $server;
foreach ( ( $server['groupLoads'] ?? [] ) as $group => $ratio ) {
$this->groupLoads[$group][$i] = $ratio;
}
$this->groupLoads[self::GROUP_GENERIC][$i] = $server['load'];
}
$this->waitTimeout = $params['waitTimeout'] ?? self::MAX_WAIT_DEFAULT;
$this->conns = self::newTrackedConnectionsArray();
if ( isset( $params['readOnlyReason'] ) && is_string( $params['readOnlyReason'] ) ) {
$this->readOnlyReason = $params['readOnlyReason'];
}
$this->loadMonitorConfig = $params['loadMonitor'] ?? [ 'class' => 'LoadMonitorNull' ];
$this->loadMonitorConfig += [ 'lagWarnThreshold' => $this->maxLag ];
$this->srvCache = $params['srvCache'] ?? new EmptyBagOStuff();
$this->wanCache = $params['wanCache'] ?? WANObjectCache::newEmpty();
$this->errorLogger = $params['errorLogger'] ?? static function ( Throwable $e ) {
trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
};
$this->deprecationLogger = $params['deprecationLogger'] ?? static function ( $msg ) {
trigger_error( $msg, E_USER_DEPRECATED );
};
$this->replLogger = $params['replLogger'] ?? new NullLogger();
$this->connLogger = $params['connLogger'] ?? new NullLogger();
$this->queryLogger = $params['queryLogger'] ?? new NullLogger();
$this->perfLogger = $params['perfLogger'] ?? new NullLogger();
$this->clusterName = $params['clusterName'] ?? null;
$this->profiler = $params['profiler'] ?? null;
$this->trxProfiler = $params['trxProfiler'] ?? new TransactionProfiler();
$this->csProvider = $params['criticalSectionProvider'] ?? null;
$this->cliMode = $params['cliMode'] ?? ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
$this->agent = $params['agent'] ?? '';
if ( isset( $params['chronologyCallback'] ) ) {
$this->chronologyCallback = $params['chronologyCallback'];
}
if ( isset( $params['roundStage'] ) ) {
if ( $params['roundStage'] === self::STAGE_POSTCOMMIT_CALLBACKS ) {
$this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
} elseif ( $params['roundStage'] === self::STAGE_POSTROLLBACK_CALLBACKS ) {
$this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
}
}
$group = $params['defaultGroup'] ?? self::GROUP_GENERIC;
$this->defaultGroup = isset( $this->groupLoads[$group] ) ? $group : self::GROUP_GENERIC;
static $nextId;
$this->id = $nextId = ( is_int( $nextId ) ? $nextId++ : mt_rand() );
$this->ownerId = $params['ownerId'] ?? null;
}
private static function newTrackedConnectionsArray() {
return [
// 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 => []
];
}
public function getClusterName(): string {
if ( $this->clusterName !== null ) {
$name = $this->clusterName;
} else {
// Fallback to the current primary name if not specified
$name = $this->getServerName( $this->getWriterIndex() );
}
return $name;
}
public function getLocalDomainID(): string {
return $this->localDomain->getId();
}
public function resolveDomainID( $domain ): string {
return $this->resolveDomainInstance( $domain )->getId();
}
/**
* @param DatabaseDomain|string|bool $domain
* @return DatabaseDomain
*/
final protected function resolveDomainInstance( $domain ): DatabaseDomain {
if ( $domain instanceof DatabaseDomain ) {
return $domain; // already a domain instance
} elseif ( $domain === false || $domain === $this->localDomain->getId() ) {
return $this->localDomain;
} elseif ( isset( $this->domainAliases[$domain] ) ) {
$this->domainAliases[$domain] =
DatabaseDomain::newFromId( $this->domainAliases[$domain] );
return $this->domainAliases[$domain];
}
$cachedDomain = $this->nonLocalDomainCache[$domain] ?? null;
if ( $cachedDomain === null ) {
$cachedDomain = DatabaseDomain::newFromId( $domain );
$this->nonLocalDomainCache = [ $domain => $cachedDomain ];
}
return $cachedDomain;
}
/**
* Resolve $groups into a list of query groups defining as having database servers
*
* @param string[]|string|bool $groups Query group(s) in preference order, [], or false
* @param int $i Specific server index or DB_PRIMARY/DB_REPLICA
* @return string[] Non-empty group list in preference order with the default group appended
*/
private function resolveGroups( $groups, $i ) {
// If a specific replica server was specified, then $groups makes no sense
if ( $i > 0 && $groups !== [] && $groups !== false ) {
$list = implode( ', ', (array)$groups );
throw new LogicException( "Query group(s) ($list) given with server index (#$i)" );
}
if ( $groups === [] || $groups === false || $groups === $this->defaultGroup ) {
$resolvedGroups = [ $this->defaultGroup ]; // common case
} elseif ( is_string( $groups ) && isset( $this->groupLoads[$groups] ) ) {
$resolvedGroups = [ $groups, $this->defaultGroup ];
} elseif ( is_array( $groups ) ) {
$resolvedGroups = $groups;
if ( array_search( $this->defaultGroup, $resolvedGroups ) === false ) {
$resolvedGroups[] = $this->defaultGroup;
}
} else {
$resolvedGroups = [ $this->defaultGroup ];
}
return $resolvedGroups;
}
/**
* @param int $flags Bitfield of class CONN_* constants
* @param int $i Specific server index or DB_PRIMARY/DB_REPLICA
* @param string $domain Database domain
* @return int Sanitized bitfield
*/
private function sanitizeConnectionFlags( $flags, $i, $domain ) {
// Whether an outside caller is explicitly requesting the primary database server
if ( $i === self::DB_PRIMARY || $i === $this->getWriterIndex() ) {
$flags |= self::CONN_INTENT_WRITABLE;
}
if ( self::fieldHasBit( $flags, self::CONN_TRX_AUTOCOMMIT ) ) {
// Callers use CONN_TRX_AUTOCOMMIT to bypass REPEATABLE-READ staleness without
// resorting to row locks (e.g. FOR UPDATE) or to make small out-of-band commits
// during larger transactions. This is useful for avoiding lock contention.
// Primary DB server attributes (should match those of the replica DB servers)
$attributes = $this->getServerAttributes( $this->getWriterIndex() );
if ( $attributes[Database::ATTR_DB_LEVEL_LOCKING] ) {
// The RDBMS does not support concurrent writes (e.g. SQLite), so attempts
// to use separate connections would just cause self-deadlocks. Note that
// REPEATABLE-READ staleness is not an issue since DB-level locking means
// that transactions are Strict Serializable anyway.
$flags &= ~self::CONN_TRX_AUTOCOMMIT;
$type = $this->getServerType( $this->getWriterIndex() );
$this->connLogger->info( __METHOD__ . ": CONN_TRX_AUTOCOMMIT disallowed ($type)" );
} elseif ( isset( $this->tempTablesOnlyMode[$domain] ) ) {
// T202116: integration tests are active and queries should be all be using
// temporary clone tables (via prefix). Such tables are not visible across
// different connections nor can there be REPEATABLE-READ snapshot staleness,
// so use the same connection for everything.
$flags &= ~self::CONN_TRX_AUTOCOMMIT;
}
}
return $flags;
}
/**
* @param IDatabase $conn
* @param int $flags
* @throws DBUnexpectedError
*/
private function enforceConnectionFlags( IDatabase $conn, $flags ) {
if ( self::fieldHasBit( $flags, self::CONN_TRX_AUTOCOMMIT ) ) {
if ( $conn->trxLevel() ) {
throw new DBUnexpectedError(
$conn,
'Handle requested with CONN_TRX_AUTOCOMMIT yet it has a transaction'
);
}
$conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
}
}
/**
* 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 string $domain Resolved DB domain
* @param int $maxLag Restrict the maximum allowed lag to this many seconds
* @return bool|int|string
*/
private function getRandomNonLagged( array $loads, string $domain, $maxLag = INF ) {
$lags = $this->getLagTimes( $domain );
# Unset excessively lagged servers
foreach ( $lags as $i => $lag ) {
if ( $i !== $this->getWriterIndex() ) {
# How much lag this server nominally is allowed to have
$maxServerLag = $this->servers[$i]['max lag'] ?? $this->maxLag; // default
# Constrain that further by $maxLag argument
$maxServerLag = min( $maxServerLag, $maxLag );
$srvName = $this->getServerName( $i );
if ( $lag === false && !is_infinite( $maxServerLag ) ) {
$this->replLogger->debug(
__METHOD__ . ": server {db_server} is not replicating?",
[ 'db_server' => $srvName ]
);
unset( $loads[$i] );
} elseif ( $lag > $maxServerLag ) {
$this->replLogger->debug(
__METHOD__ .
": server {db_server} has {lag} seconds of lag (>= {maxlag})",
[ 'db_server' => $srvName, '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 primary and some replica DBs with zero load
# Do NOT use the primary DB
# 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 );
}
/**
* Get the server index to use for a specified server index and query group list
*
* @param int $i Specific server index or DB_PRIMARY/DB_REPLICA
* @param string[] $groups Non-empty query group list in preference order
* @param string|bool $domain
* @return int A specific server index (replica DBs are checked for connectivity)
*/
private function getConnectionIndex( $i, array $groups, $domain ) {
if ( $i === self::DB_PRIMARY ) {
$i = $this->getWriterIndex();
} elseif ( $i === self::DB_REPLICA ) {
foreach ( $groups as $group ) {
$groupIndex = $this->getReaderIndex( $group, $domain );
if ( $groupIndex !== false ) {
$i = $groupIndex; // group connection succeeded
break;
}
}
} elseif ( !isset( $this->servers[$i] ) ) {
throw new UnexpectedValueException( "Invalid server index index #$i" );
}
if ( $i === self::DB_REPLICA ) {
$this->lastError = 'Unknown error'; // set here in case of worse failure
$this->lastError = 'No working replica DB server: ' . $this->lastError;
$this->reportConnectionError();
}
return $i;
}
public function getReaderIndex( $group = false, $domain = false ) {
$domain = $this->resolveDomainID( $domain );
$group = is_string( $group ) ? $group : self::GROUP_GENERIC;
if ( $this->getServerCount() == 1 ) {
// Skip the load balancing if there's only one server
return $this->getWriterIndex();
}
$index = $this->getExistingReaderIndex( $group );
if ( $index !== self::READER_INDEX_NONE ) {
// A reader index was already selected and "waitForPos" was handled
return $index;
}
// Use the server weight array for this load group
if ( isset( $this->groupLoads[$group] ) ) {
$loads = $this->groupLoads[$group];
} else {
$this->connLogger->info( __METHOD__ . ": no loads for group $group" );
return false;
}
// 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"
$this->lazyLoadReplicationPositions(); // optimizes server candidate selection
list( $i, $laggedReplicaMode ) = $this->pickReaderIndex( $loads, $domain );
if ( $i === false ) {
// DB connection unsuccessful
return false;
}
// If data seen by queries is expected to reflect the transactions committed as of
// or after a given replication position then wait for the DB to apply those changes
if ( $this->waitForPos && $i !== $this->getWriterIndex() && !$this->doWait( $i ) ) {
// Data will be outdated compared to what was expected
$laggedReplicaMode = true;
}
// Cache the reader index for future DB_REPLICA handles
$this->setExistingReaderIndex( $group, $i );
// Record whether the generic reader index is in "lagged replica DB" mode
if ( $group === self::GROUP_GENERIC && $laggedReplicaMode ) {
$this->laggedReplicaMode = true;
$this->replLogger->debug( __METHOD__ . ": setting lagged replica mode" );
}
$serverName = $this->getServerName( $i );
$this->connLogger->debug( __METHOD__ . ": using server $serverName for group '$group'" );
return $i;
}
/**
* Get the server index chosen by the load balancer for use with the given query group
*
* @param string $group Query group; use false for the generic group
* @return int Server index or LoadBalancer::READER_INDEX_NONE if none was chosen
*/
protected function getExistingReaderIndex( $group ) {
return $this->readIndexByGroup[$group] ?? self::READER_INDEX_NONE;
}
/**
* Set the server index chosen by the load balancer for use with the given query group
*
* @param string $group Query group; use false for the generic group
* @param int $index The index of a specific server
*/
private function setExistingReaderIndex( $group, $index ) {
if ( $index < 0 ) {
throw new UnexpectedValueException( "Cannot set a negative read server index" );
}
$this->readIndexByGroup[$group] = $index;
}
/**
* Pick a server that is reachable, preferably non-lagged, and return its server index
*
* This will leave the server connection open within the pool for reuse
*
* @param array $loads List of server weights
* @param string $domain Resolved DB domain
* @return array (reader index, lagged replica mode) or (false, false) on failure
*/
private function pickReaderIndex( array $loads, string $domain ) {
if ( $loads === [] ) {
throw new InvalidArgumentException( "Server configuration array is empty" );
}
/** @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 ( $laggedReplicaMode ) {
$i = ArrayUtils::pickRandom( $currentLoads );
} else {
$i = false;
if ( $this->waitForPos && $this->waitForPos->asOfTime() ) {
$this->replLogger->debug( __METHOD__ . ": replication positions detected" );
// "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 ) ) {
// All replica DBs lagged. Switch to read-only mode
$this->replLogger->error(
__METHOD__ . ": all replica DBs lagged. Switch to read-only mode",
[ 'db_domain' => $domain ]
);
$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..." );
// Get a connection to this server without triggering complementary connections
// to other servers (due to things like lag or read-only checks). We want to avoid
// the risk of overhead and recursion here.
$conn = $this->getServerConnection( $i, $domain, self::CONN_SILENCE_ERRORS );
if ( !$conn ) {
$this->connLogger->warning(
__METHOD__ . ": failed connecting to $i/{db_domain}",
[ 'db_domain' => $domain ]
);
unset( $currentLoads[$i] ); // avoid this server next iteration
$i = false;
continue;
}
// Decrement reference counter, we are finished with this connection.
// It will be incremented for the caller later.
if ( !$this->localDomain->equals( $domain ) ) {
$this->reuseConnection( $conn );
}
// Return this server
break;
}
// If all servers were down, quit now
if ( $currentLoads === [] ) {
$this->connLogger->error(
__METHOD__ . ": all servers down",
[ 'db_domain' => $domain ]
);
}
return [ $i, $laggedReplicaMode ];
}
public function waitFor( $pos ) {
$oldPos = $this->waitForPos;
try {
$this->waitForPos = $pos;
$genericIndex = $this->getExistingReaderIndex( self::GROUP_GENERIC );
// If a generic reader connection was already established, then wait now.
// Otherwise, wait until a connection is established in getReaderIndex().
if ( $genericIndex > $this->getWriterIndex() && !$this->doWait( $genericIndex ) ) {
$this->laggedReplicaMode = true;
$this->replLogger->debug( __METHOD__ . ": setting lagged replica mode" );
}
} finally {
// Restore the older position if it was higher since this is used for lag-protection
$this->setWaitForPositionIfHigher( $oldPos );
}
}
public function waitForAll( $pos, $timeout = null ) {
$timeout = $timeout ?: $this->waitTimeout;
$oldPos = $this->waitForPos;
try {
$this->waitForPos = $pos;
$ok = true;
foreach ( $this->getStreamingReplicaIndexes() as $i ) {
if ( $this->serverHasLoadInAnyGroup( $i ) ) {
$start = microtime( true );
$ok = $this->doWait( $i, $timeout ) && $ok;
$timeout -= intval( microtime( true ) - $start );
if ( $timeout <= 0 ) {
break; // timeout reached
}
}
}
return $ok;
} finally {
// Restore the old position; this is used for throttling, not lag-protection
$this->waitForPos = $oldPos;
}
}
/**
* @param int $i Specific server index
* @return bool
*/
private function serverHasLoadInAnyGroup( $i ) {
foreach ( $this->groupLoads as $loadsByIndex ) {
if ( ( $loadsByIndex[$i] ?? 0 ) > 0 ) {
return true;
}
}
return false;
}
/**
* @param DBPrimaryPos|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 ) {
$i = ( $i === self::DB_PRIMARY ) ? $this->getWriterIndex() : $i;
// Connection handles required to be in auto-commit mode use a separate connection
// pool since the main pool is effected by implicit and explicit transaction rounds
$autoCommitOnly = self::fieldHasBit( $flags, self::CONN_TRX_AUTOCOMMIT );
$conn = false;
foreach ( $this->conns as $type => $connsByServer ) {
if ( $i === self::DB_REPLICA ) {
// Consider all existing connections to any server
$applicableConnsByServer = $connsByServer;
} else {
// Consider all existing connections to a specific server
$applicableConnsByServer = isset( $connsByServer[$i] )
? [ $i => $connsByServer[$i] ]
: [];
}
$conn = $this->pickAnyOpenConnection( $applicableConnsByServer, $autoCommitOnly );
if ( $conn ) {
$this->connLogger->debug( __METHOD__ . ": found '$type' connection to #$i." );
break;
}
}
if ( $conn ) {
$this->enforceConnectionFlags( $conn, $flags );
}
return $conn;
}
/**
* @param Database[][] $connsByServer Map of (server index => array of DB handles)
* @param bool $autoCommitOnly Whether to only look for auto-commit connections
* @return IDatabase|false An appropriate open connection or false if none found
*/
private function pickAnyOpenConnection( array $connsByServer, $autoCommitOnly ) {
foreach ( $connsByServer as $i => $conns ) {
foreach ( $conns as $conn ) {
if ( !$conn->isOpen() ) {
$this->connLogger->warning(
__METHOD__ .
": pooled DB handle for {db_server} (#$i) has no open connection.",
$this->getConnLogContext( $conn )
);
continue; // some sort of error occurred?
}
if ( $autoCommitOnly ) {
// Only accept CONN_TRX_AUTOCOMMIT connections
if ( !$conn->getLBInfo( self::INFO_AUTOCOMMIT_ONLY ) ) {
// Connection is aware of transaction rounds
continue;
}
if ( $conn->trxLevel() ) {
// Some sort of bug left a transaction open
$this->connLogger->warning(
__METHOD__ .
": pooled DB handle for {db_server} (#$i) has a pending transaction.",
$this->getConnLogContext( $conn )
);
continue;
}
}
return $conn;
}
}
return false;
}
/**
* Wait for a given replica DB to catch up to the primary DB pos stored in "waitForPos"
*
* @param int $index Specific server index
* @param int|null $timeout Max seconds to wait; default is "waitTimeout"
* @return bool
*/
private function doWait( $index, $timeout = null ) {
$timeout = max( 1, intval( $timeout ?: $this->waitTimeout ) );
// Check if we already know that the DB has reached this point
$srvName = $this->getServerName( $index );
$key = $this->srvCache->makeGlobalKey( __CLASS__, 'last-known-pos', $srvName, 'v1' );
/** @var DBPrimaryPos $knownReachedPos */
$knownReachedPos = $this->srvCache->get( $key );
if (
$knownReachedPos instanceof DBPrimaryPos &&
$knownReachedPos->hasReached( $this->waitForPos )
) {
$this->replLogger->debug(
__METHOD__ .
": replica DB {db_server} known to be caught up (pos >= $knownReachedPos).",
[ 'db_server' => $srvName ]
);
return true;
}
$close = false; // close the connection afterwards
$flags = self::CONN_SILENCE_ERRORS;
// Check if there is an existing connection that can be used
$conn = $this->getAnyOpenConnection( $index, $flags );
if ( !$conn ) {
// Get a connection to this server without triggering complementary connections
// to other servers (due to things like lag or read-only checks). We want to avoid
// the risk of overhead and recursion here.
$conn = $this->getServerConnection( $index, self::DOMAIN_ANY, $flags );
if ( !$conn ) {
$this->replLogger->warning(
__METHOD__ . ': failed to connect to {db_server}',
[ 'db_server' => $srvName ]
);
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 {db_server} to catch up...',
$this->getConnLogContext( $conn )
);
$result = $conn->primaryPosWait( $this->waitForPos, $timeout );
$ok = ( $result !== null && $result != -1 );
if ( $ok ) {
// 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 ) {
$domain = $this->resolveDomainID( $domain );
$groups = $this->resolveGroups( $groups, $i );
$flags = $this->sanitizeConnectionFlags( $flags, $i, $domain );
// If given DB_PRIMARY/DB_REPLICA, resolve it to a specific server index. Resolving
// DB_REPLICA might trigger getServerConnection() calls due to the getReaderIndex()
// connectivity checks or LoadMonitor::scaleLoads() server state cache regeneration.
// The use of getServerConnection() instead of getConnection() avoids infinite loops.
$serverIndex = $this->getConnectionIndex( $i, $groups, $domain );
// Get an open connection to that server (might trigger a new connection)
$conn = $this->getServerConnection( $serverIndex, $domain, $flags );
// Set primary DB handles as read-only if there is high replication lag
if (
$conn &&
$serverIndex === $this->getWriterIndex() &&
$this->getLaggedReplicaMode( $domain ) &&
!is_string( $conn->getLBInfo( $conn::LB_READ_ONLY_REASON ) )
) {
$genericIndex = $this->getExistingReaderIndex( self::GROUP_GENERIC );
$reason = ( $genericIndex !== self::READER_INDEX_NONE )
? 'The database is read-only until replication lag decreases.'
: 'The database is read-only until replica database servers becomes reachable.';
$conn->setLBInfo( $conn::LB_READ_ONLY_REASON, $reason );
}
return $conn;
}
public function getServerConnection( $i, $domain, $flags = 0 ) {
// Number of connections made before getting the server index and handle
$priorConnectionsMade = $this->connectionCounter;
// Get an open connection to this server (might trigger a new connection)
$conn = $this->localDomain->equals( $domain )
? $this->getLocalConnection( $i, $flags )
: $this->getForeignConnection( $i, $domain, $flags );
// Throw an error or otherwise bail out if the connection attempt failed
if ( !( $conn instanceof IDatabase ) ) {
if ( !self::fieldHasBit( $flags, self::CONN_SILENCE_ERRORS ) ) {
$this->reportConnectionError();
}
return false;
}
// Profile any new connections caused by this method
if ( $this->connectionCounter > $priorConnectionsMade ) {
$this->trxProfiler->recordConnection(
$conn->getServerName(),
$conn->getDBname(),
self::fieldHasBit( $flags, self::CONN_INTENT_WRITABLE )
);
}
if ( !$conn->isOpen() ) {
$this->errorConnection = $conn;
// 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.
// FIXME: report an error here unless CONN_SILENCE_ERRORS was set
return false;
}
// Make sure that flags like CONN_TRX_AUTOCOMMIT are respected by this handle
$this->enforceConnectionFlags( $conn, $flags );
// Set primary DB handles as read-only if the load balancer is configured as read-only
// or the primary database server is running in server-side read-only mode. Note that
// replica DB handles are always read-only via Database::assertIsWritablePrimary().
// Read-only mode due to replication lag is *avoided* here to avoid recursion.
if ( $i === $this->getWriterIndex() ) {
if ( $this->readOnlyReason !== false ) {
$readOnlyReason = $this->readOnlyReason;
} elseif ( $this->isPrimaryConnectionReadOnly( $conn, $flags ) ) {
$readOnlyReason = 'The primary database server is running in read-only mode.';
} else {
$readOnlyReason = false;
}
$conn->setLBInfo( $conn::LB_READ_ONLY_REASON, $readOnlyReason );
}
return $conn;
}
public function reuseConnection( IDatabase $conn ) {
$serverIndex = $conn->getLBInfo( self::INFO_SERVER_INDEX );
$refCount = $conn->getLBInfo( self::INFO_FOREIGN_REF_COUNT );
if ( $serverIndex === null || $refCount === null ) {
return; // non-foreign connection; no domain-use tracking to update
} 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",
[ 'db_domain' => $conn->getDomainID(), 'exception' => new RuntimeException() ]
);
return;
}
if ( $this->disabled ) {
return; // DBConnRef handle probably survived longer than the LoadBalancer
}
if ( $conn->getLBInfo( self::INFO_AUTOCOMMIT_ONLY ) ) {
$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();
$existingDomainConn = $this->conns[$connInUseKey][$serverIndex][$domain] ?? null;
if ( !$existingDomainConn ) {
throw new InvalidArgumentException(
"Connection $serverIndex/$domain not found; it may have already been freed" );
} elseif ( $existingDomainConn !== $conn ) {
throw new InvalidArgumentException(
"Connection $serverIndex/$domain mismatched; it may have already been freed" );
}
$existingDomainConn->setLBInfo( self::INFO_FOREIGN_REF_COUNT, --$refCount );
if ( $refCount <= 0 ) {
$this->conns[$connFreeKey][$serverIndex][$domain] = $existingDomainConn;
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( $i, $groups = [], $domain = false, $flags = 0 ): IDatabase {
if ( self::fieldHasBit( $flags, self::CONN_SILENCE_ERRORS ) ) {
throw new UnexpectedValueException(
__METHOD__ . ' CONN_SILENCE_ERRORS is not supported'
);
}
$domain = $this->resolveDomainID( $domain );
$role = $this->getRoleFromIndex( $i );
$conn = $this->getConnection( $i, $groups, $domain, $flags );
return new DBConnRef( $this, $conn, $role );
}
public function getLazyConnectionRef( $i, $groups = [], $domain = false, $flags = 0 ): DBConnRef {
if ( self::fieldHasBit( $flags, self::CONN_SILENCE_ERRORS ) ) {
throw new UnexpectedValueException(
__METHOD__ . ' got CONN_SILENCE_ERRORS; connection is already deferred'
);
}
$domain = $this->resolveDomainID( $domain );
$role = $this->getRoleFromIndex( $i );
return new DBConnRef( $this, [ $i, $groups, $domain, $flags ], $role );
}
public function getMaintenanceConnectionRef(
$i,
$groups = [],
$domain = false,
$flags = 0
): MaintainableDBConnRef {
if ( self::fieldHasBit( $flags, self::CONN_SILENCE_ERRORS ) ) {
throw new UnexpectedValueException(
__METHOD__ . ' CONN_SILENCE_ERRORS is not supported'
);
}
$domain = $this->resolveDomainID( $domain );
$role = $this->getRoleFromIndex( $i );
$conn = $this->getConnection( $i, $groups, $domain, $flags );
return new MaintainableDBConnRef( $this, $conn, $role );
}
/**
* @param int $i Server index or DB_PRIMARY/DB_REPLICA
* @return int One of DB_PRIMARY/DB_REPLICA
*/
private function getRoleFromIndex( $i ) {
return ( $i === self::DB_PRIMARY || $i === $this->getWriterIndex() )
? self::DB_PRIMARY
: self::DB_REPLICA;
}
/**
* @param int $i
* @param string|bool $domain
* @param int $flags
* @return Database|bool Live database handle or false on failure
* @deprecated Since 1.34 Use getConnection() instead
*/
public function openConnection( $i, $domain = false, $flags = 0 ) {
return $this->getConnection( $i, [], $domain, $flags | self::CONN_SILENCE_ERRORS );
}
/**
* Open a connection to a local DB, or return one if it is already open.
*
* 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 Specific server index
* @param int $flags Class CONN_* constant bitfield
* @return Database
* @throws InvalidArgumentException When the server index is invalid
* @throws UnexpectedValueException When the DB domain of the connection is corrupted
*/
private function getLocalConnection( $i, $flags = 0 ) {
$autoCommit = self::fieldHasBit( $flags, self::CONN_TRX_AUTOCOMMIT );
// Connection handles required to be in auto-commit mode use a separate connection
// pool since the main pool is effected by implicit and explicit transaction rounds
$connKey = $autoCommit ? self::KEY_LOCAL_NOROUND : self::KEY_LOCAL;
if ( isset( $this->conns[$connKey][$i][self::KEY_LOCAL_DOMAIN] ) ) {
$conn = $this->conns[$connKey][$i][self::KEY_LOCAL_DOMAIN];
$this->connLogger->debug( __METHOD__ . ": reused a connection for $connKey/$i" );
} else {
$conn = $this->reallyOpenConnection(
$i,
$this->localDomain,
[ self::INFO_AUTOCOMMIT_ONLY => $autoCommit ]
);
if ( $conn->isOpen() ) {
$this->connLogger->debug( __METHOD__ . ": opened new connection for $connKey/$i" );
$this->conns[$connKey][$i][self::KEY_LOCAL_DOMAIN] = $conn;
} else {
$this->connLogger->warning( __METHOD__ . ": connection error for $connKey/$i" );
$this->errorConnection = $conn;
$conn = false;
}
}
// Check to make sure that the right domain is selected
if (
$conn instanceof IDatabase &&
!$this->localDomain->isCompatible( $conn->getDomainID() )
) {
throw new UnexpectedValueException(
"Got connection to '{$conn->getDomainID()}', " .
"but expected local domain ('{$this->localDomain}')"
);
}
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 Specific server index
* @param string $domain Domain ID to open
* @param int $flags Class CONN_* constant bitfield
* @return Database|bool Returns false on connection error
* @throws DBError When database selection fails
* @throws InvalidArgumentException When the server index is invalid
* @throws UnexpectedValueException When the DB domain of the connection is corrupted
*/
private function getForeignConnection( $i, $domain, $flags = 0 ) {
$domainInstance = DatabaseDomain::newFromId( $domain );
$autoCommit = self::fieldHasBit( $flags, self::CONN_TRX_AUTOCOMMIT );
// Connection handles required to be in auto-commit mode use a separate connection
// pool since the main pool is effected by implicit and explicit transaction rounds
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;
}
/** @var Database $conn */
$conn = null;
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 $connInUseKey/$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 $connInUseKey/$i/$domain" );
} elseif ( !empty( $this->conns[$connFreeKey][$i] ) ) {
// Reuse a free connection from another domain if possible
foreach ( $this->conns[$connFreeKey][$i] as $oldDomain => $oldConn ) {
if ( $domainInstance->getDatabase() !== null ) {
// Check if changing the database will require a new connection.
// In that case, leave the connection handle alone and keep looking.
// This prevents connections from being closed mid-transaction and can
// also avoid overhead if the same database will later be requested.
if (
$oldConn->databasesAreIndependent() &&
$oldConn->getDBname() !== $domainInstance->getDatabase()
) {
continue;
}
// Select the new database, schema, and prefix
$conn = $oldConn;
$conn->selectDomain( $domainInstance );
} else {
// Stay on the current database, but update the schema/prefix
$conn = $oldConn;
$conn->dbSchema( $domainInstance->getSchema() );
$conn->tablePrefix( $domainInstance->getTablePrefix() );
}
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 $domain" );
break;
}
}
if ( !$conn ) {
$conn = $this->reallyOpenConnection(
$i,
$domainInstance,
[
self::INFO_AUTOCOMMIT_ONLY => $autoCommit,
self::INFO_FORIEGN => true,
self::INFO_FOREIGN_REF_COUNT => 0
]
);
if ( $conn->isOpen() ) {
// 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 $connInUseKey/$i/$domain" );
} else {
$this->connLogger->warning(
__METHOD__ . ": connection error for $connInUseKey/$i/{db_domain}",
[ 'db_domain' => $domain ]
);
$this->errorConnection = $conn;
$conn = false;
}
}
if ( $conn instanceof IDatabase ) {
// Check to make sure that the right domain is selected
if ( !$domainInstance->isCompatible( $conn->getDomainID() ) ) {
throw new UnexpectedValueException(
"Got connection to '{$conn->getDomainID()}', but expected '$domain'" );
}
// Increment reference count
$refCount = $conn->getLBInfo( self::INFO_FOREIGN_REF_COUNT );
$conn->setLBInfo( self::INFO_FOREIGN_REF_COUNT, $refCount + 1 );
}
return $conn;
}
public function getServerAttributes( $i ) {
return Database::attributesFromType(
$this->getServerType( $i ),
$this->servers[$i]['driver'] ?? null
);
}
/**
* Test if the specified index represents an open connection
*
* @param int $index Server index
* @return bool
*/
private function isOpen( $index ) {
return (bool)$this->getAnyOpenConnection( $index );
}
/**
* Open a new network connection to a server (uncached)
*
* Returns a Database object whether or not the connection was successful.
*
* @param int $i Specific server index
* @param DatabaseDomain $domain Domain the connection is for, possibly unspecified
* @param array $lbInfo Additional information for setLBInfo()
* @return IDatabase
* @throws DBAccessError
* @throws InvalidArgumentException
*/
protected function reallyOpenConnection( $i, DatabaseDomain $domain, array $lbInfo ) {
if ( $this->disabled ) {
throw new DBAccessError();
}
$server = $this->getServerInfoStrict( $i );
$conn = Database::factory(
$server['type'],
array_merge( $server, [
// Basic replication role information
'topologyRole' => $this->getTopologyRole( $i, $server ),
'topologicalMaster' => $this->getPrimaryServerName(),
// Use the database specified in $domain (null means "none or entrypoint DB");
// fallback to the $server default if the RDBMs is an embedded library using a
// file on disk since there would be nothing to access to without a DB/file name.
'dbname' => $this->getServerAttributes( $i )[Database::ATTR_DB_IS_FILE]
? ( $domain->getDatabase() ?? $server['dbname'] ?? null )
: $domain->getDatabase(),
// Override the $server default schema with that of $domain if specified
'schema' => $domain->getSchema() ?? $server['schema'] ?? null,
// Use the table prefix specified in $domain
'tablePrefix' => $domain->getTablePrefix(),
// Participate in transaction rounds if $server does not specify otherwise
'flags' => $this->initConnFlags( $server['flags'] ?? IDatabase::DBO_DEFAULT ),
// Inject the PHP execution mode and the agent string
'cliMode' => $this->cliMode,
'agent' => $this->agent,
'ownerId' => $this->id,
// Inject object and callback dependencies
'lazyMasterHandle' => $this->getLazyConnectionRef(
self::DB_PRIMARY,
[],
$domain->getId()
),
'srvCache' => $this->srvCache,
'connLogger' => $this->connLogger,
'queryLogger' => $this->queryLogger,
'replLogger' => $this->replLogger,
'errorLogger' => $this->errorLogger,
'deprecationLogger' => $this->deprecationLogger,
'profiler' => $this->profiler,
'trxProfiler' => $this->trxProfiler,
'criticalSectionProvider' => $this->csProvider
] ),
Database::NEW_UNCONNECTED
);
// Attach load balancer information to the handle
$conn->setLBInfo( [ self::INFO_SERVER_INDEX => $i ] + $lbInfo );
// Set alternative table/index names before any queries can be issued
$conn->setTableAliases( $this->tableAliases );
$conn->setIndexAliases( $this->indexAliases );
// Account for any active transaction round and listeners
if ( $i === $this->getWriterIndex() ) {
if ( $this->trxRoundId !== false ) {
$this->applyTransactionRoundFlags( $conn );
}
foreach ( $this->trxRecurringCallbacks as $name => $callback ) {
$conn->setTransactionListener( $name, $callback );
}
}
// Make the connection handle live
try {
$conn->initConnection();
++$this->connectionCounter;
} catch ( DBConnectionError $e ) {
// ignore; let the DB handle the logging
}
// Try to maintain session consistency for clients that trigger write transactions
// in a request or script and then return soon after in another request or script.
// This requires cooperation with ChronologyProtector and the application wiring.
if ( $conn->isOpen() ) {
$this->lazyLoadReplicationPositions();
}
// Log when many connection are made during a single request/script
$count = $this->getCurrentConnectionCount();
if ( $count >= self::CONN_HELD_WARN_THRESHOLD ) {
$this->perfLogger->warning(
__METHOD__ . ": {connections}+ connections made (primary={primarydb})",
$this->getConnLogContext(
$conn,
[
'connections' => $count,
'primarydb' => $this->getPrimaryServerName(),
'db_domain' => $domain->getId()
]
)
);
}
return $conn;
}
/**
* @param int $i Specific server index
* @param array $server Server config map
* @return string IDatabase::ROLE_* constant
*/
private function getTopologyRole( $i, array $server ) {
if ( !empty( $server['is static'] ) ) {
return IDatabase::ROLE_STATIC_CLONE;
}
return ( $i === $this->getWriterIndex() )
? IDatabase::ROLE_STREAMING_MASTER
: IDatabase::ROLE_STREAMING_REPLICA;
}
/**
* @see IDatabase::DBO_DEFAULT
* @param int $flags Bit field of IDatabase::DBO_* constants from configuration
* @return int Bit field of IDatabase::DBO_* constants to use with Database::factory()
*/
private function initConnFlags( $flags ) {
if ( self::fieldHasBit( $flags, IDatabase::DBO_DEFAULT ) ) {
if ( $this->cliMode ) {
$flags &= ~IDatabase::DBO_TRX;
} else {
$flags |= IDatabase::DBO_TRX;
}
}
return $flags;
}
/**
* Make sure that any "waitForPos" positions are loaded and available to doWait()
*/
private function lazyLoadReplicationPositions() {
if ( !$this->chronologyCallbackTriggered && $this->chronologyCallback ) {
$this->chronologyCallbackTriggered = true;
( $this->chronologyCallback )( $this ); // generally calls waitFor()
$this->connLogger->debug( __METHOD__ . ': executed chronology callback.' );
}
}
/**
* @throws DBConnectionError
* @return never
*/
private function reportConnectionError() {
$conn = $this->errorConnection; // the connection which caused the error
$context = [
'method' => __METHOD__,
'last_error' => $this->lastError,
];
if ( $conn instanceof IDatabase ) {
$srvName = $conn->getServerName();
$this->connLogger->warning(
__METHOD__ . ": connection error: {last_error} ({db_server})",
$this->getConnLogContext( $conn, $context )
);
$error = $conn->lastError() ?: $this->lastError;
throw new DBConnectionError( $conn, "{$error} ($srvName)" );
} 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;
}
/**
* Returns true if the specified index is a valid server index
*
* @param int $i
* @return bool
* @deprecated Since 1.34
*/
public function haveIndex( $i ) {
return array_key_exists( $i, $this->servers );
}
/**
* Returns true if the specified index is valid and has non-zero load
*
* @param int $i
* @return bool
* @deprecated Since 1.34
*/
public function isNonZeroLoad( $i ) {
return ( isset( $this->servers[$i] ) && $this->groupLoads[self::GROUP_GENERIC][$i] > 0 );
}
public function getServerCount() {
return count( $this->servers );
}
public function hasReplicaServers() {
return ( $this->getServerCount() > 1 );
}
/**
* @return int[] List of replica server indexes
*/
private function getStreamingReplicaIndexes() {
$indexes = [];
foreach ( $this->servers as $i => $server ) {
if ( $i !== $this->getWriterIndex() && empty( $server['is static'] ) ) {
$indexes[] = $i;
}
}
return $indexes;
}
public function hasStreamingReplicaServers() {
return (bool)$this->getStreamingReplicaIndexes();
}
public function getServerName( $i ): string {
$name = $this->servers[$i]['serverName'] ?? ( $this->servers[$i]['host'] ?? '' );
return ( $name !== '' ) ? $name : 'localhost';
}
public function getServerInfo( $i ) {
return $this->servers[$i] ?? false;
}
public function getServerType( $i ) {
return $this->servers[$i]['type'] ?? 'unknown';
}
public function getPrimaryPos() {
$index = $this->getWriterIndex();
$conn = $this->getAnyOpenConnection( $index );
if ( $conn ) {
return $conn->getPrimaryPos();
}
$conn = $this->getConnection( $index, self::CONN_SILENCE_ERRORS );
if ( !$conn ) {
$this->reportConnectionError();
}
try {
return $conn->getPrimaryPos();
} finally {
$this->closeConnection( $conn );
}
}
public function getReplicaResumePos() {
// Get the position of any existing primary DB server connection
$primaryConn = $this->getAnyOpenConnection( $this->getWriterIndex() );
if ( $primaryConn ) {
return $primaryConn->getPrimaryPos();
}
// Get the highest position of any existing replica server connection
$highestPos = false;
foreach ( $this->getStreamingReplicaIndexes() as $i ) {
$conn = $this->getAnyOpenConnection( $i );
$pos = $conn ? $conn->getReplicaPos() : false;
if ( !$pos ) {
continue; // no open connection or could not get position
}
$highestPos = $highestPos ?: $pos;
if ( $pos->hasReached( $highestPos ) ) {
$highestPos = $pos;
}
}
return $highestPos;
}
public function disable( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
$this->closeAll( $fname, $owner );
$this->disabled = true;
}
public function closeAll( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
if ( $this->ownerId === null ) {
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = ScopedCallback::newScopedIgnoreUserAbort();
}
$this->forEachOpenConnection( function ( IDatabase $conn ) use ( $fname ) {
$srvName = $conn->getServerName();
$this->connLogger->debug( "$fname: closing connection to database '$srvName'." );
$conn->close( $fname, $this->id );
} );
$this->conns = self::newTrackedConnectionsArray();
}
public function closeConnection( IDatabase $conn ) {
if ( $conn instanceof DBConnRef ) {
// Avoid calling close() but still leaving the handle in the pool
throw new RuntimeException( 'Cannot close DBConnRef instance; it must be shareable' );
}
$serverIndex = $conn->getLBInfo( self::INFO_SERVER_INDEX );
if ( $serverIndex === null ) {
throw new RuntimeException( 'Database handle is missing server index' );
}
$srvName = $this->getServerName( $serverIndex );
$domain = $conn->getDomainID();
$found = false;
foreach ( $this->conns as $type => $connsByServer ) {
$key = array_search( $conn, $connsByServer[$serverIndex] ?? [], true );
if ( $key !== false ) {
$found = true;
unset( $this->conns[$type][$serverIndex][$key] );
}
}
if ( !$found ) {
$this->connLogger->warning(
__METHOD__ .
": got orphaned connection to database $serverIndex/$domain at '$srvName'."
);
}
$this->connLogger->debug(
__METHOD__ .
": closing connection to database $serverIndex/$domain at '$srvName'."
);
$conn->close( __METHOD__ );
}
public function commitAll( $fname = __METHOD__, $owner = null ) {
$this->commitPrimaryChanges( $fname, $owner );
$this->flushPrimarySnapshots( $fname, $owner );
$this->flushReplicaSnapshots( $fname, $owner );
}
public function finalizePrimaryChanges( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
$this->assertTransactionRoundStage( [ self::ROUND_CURSORY, self::ROUND_FINALIZED ] );
if ( $this->ownerId === null ) {
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = ScopedCallback::newScopedIgnoreUserAbort();
}
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
// Loop until callbacks stop adding callbacks on other connections
$total = 0;
do {
$count = 0; // callbacks execution attempts
$this->forEachOpenPrimaryConnection( static function ( Database $conn ) use ( &$count ) {
// Run any pre-commit callbacks while leaving the post-commit ones suppressed.
// Any error should cause all (peer) transactions to be rolled back together.
$count += $conn->runOnTransactionPreCommitCallbacks();
} );
$total += $count;
} while ( $count > 0 );
// Defer post-commit callbacks until after COMMIT/ROLLBACK happens on all handles
$this->forEachOpenPrimaryConnection( static function ( Database $conn ) {
$conn->setTrxEndCallbackSuppression( true );
} );
$this->trxRoundStage = self::ROUND_FINALIZED;
return $total;
}
public function approvePrimaryChanges( array $options, $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
$this->assertTransactionRoundStage( self::ROUND_FINALIZED );
if ( $this->ownerId === null ) {
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = ScopedCallback::newScopedIgnoreUserAbort();
}
$limit = $options['maxWriteDuration'] ?? 0;
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
$this->forEachOpenPrimaryConnection( function ( IDatabase $conn ) use ( $limit ) {
// Any atomic sections should have been closed by now and there definitely should
// not be any open transactions started by begin() from callers outside Database.
if ( $conn->explicitTrxActive() ) {
throw new DBTransactionError(
$conn,
"Explicit transaction still active; a caller might have failed to call " .
"endAtomic() or cancelAtomic()."
);
}
// Assert that the time to replicate the transaction will be reasonable.
// If this fails, then all DB transactions will be rollback back together.
$time = $conn->pendingWriteQueryDuration( $conn::ESTIMATE_DB_APPLY );
if ( $limit > 0 ) {
if ( $time > $limit ) {
$humanTimeSec = round( $time, 3 );
throw new DBTransactionSizeError(
$conn,
"Transaction spent {$humanTimeSec}s in writes, exceeding the {$limit}s limit",
// Message parameters for: transaction-duration-limit-exceeded
[ $time, $limit ]
);
} elseif ( $time > 0 ) {
$timeMs = $time * 1000;
$humanTimeMs = $timeMs > 1 ? round( $timeMs ) : round( $timeMs, 3 );
$this->perfLogger->debug(
"Transaction spent {time_ms}ms in writes, under the {$limit}s limit",
[ 'time_ms' => $humanTimeMs ]
);
}
}
// 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"
);
}
} );
$this->trxRoundStage = self::ROUND_APPROVED;
}
public function beginPrimaryChanges( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
if ( $this->trxRoundId !== false ) {
throw new DBTransactionError(
null,
"$fname: Transaction round '{$this->trxRoundId}' already started"
);
}
$this->assertTransactionRoundStage( self::ROUND_CURSORY );
if ( $this->ownerId === null ) {
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = ScopedCallback::newScopedIgnoreUserAbort();
}
// Clear any empty transactions (no writes/callbacks) from the implicit round
$this->flushPrimarySnapshots( $fname, $owner );
$this->trxRoundId = $fname;
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
// Mark applicable handles as participating in this explicit transaction round.
// For each of these handles, any writes and callbacks will be tied to a single
// transaction. The (peer) handles will reject begin()/commit() calls unless they
// are part of an en masse commit or an en masse rollback.
$this->forEachOpenPrimaryConnection( function ( Database $conn ) {
$this->applyTransactionRoundFlags( $conn );
} );
$this->trxRoundStage = self::ROUND_CURSORY;
}
public function commitPrimaryChanges( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
$this->assertTransactionRoundStage( self::ROUND_APPROVED );
if ( $this->ownerId === null ) {
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = ScopedCallback::newScopedIgnoreUserAbort();
}
$failures = [];
$restore = ( $this->trxRoundId !== false );
$this->trxRoundId = false;
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
// Commit any writes and clear any snapshots as well (callbacks require AUTOCOMMIT).
// Note that callbacks should already be suppressed due to finalizePrimaryChanges().
$this->forEachOpenPrimaryConnection(
function ( IDatabase $conn ) use ( $fname, &$failures ) {
try {
$conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
} catch ( DBError $e ) {
( $this->errorLogger )( $e );
$failures[] = "{$conn->getServerName()}: {$e->getMessage()}";
}
}
);
if ( $failures ) {
throw new DBTransactionError(
null,
"$fname: Commit failed on server(s) " . implode( "\n", array_unique( $failures ) )
);
}
if ( $restore ) {
// Unmark handles as participating in this explicit transaction round
$this->forEachOpenPrimaryConnection( function ( Database $conn ) {
$this->undoTransactionRoundFlags( $conn );
} );
}
$this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
}
public function runPrimaryTransactionIdleCallbacks( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
$type = IDatabase::TRIGGER_COMMIT;
} elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
$type = IDatabase::TRIGGER_ROLLBACK;
} else {
throw new DBTransactionError(
null,
"Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
);
}
if ( $this->ownerId === null ) {
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = ScopedCallback::newScopedIgnoreUserAbort();
}
$oldStage = $this->trxRoundStage;
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
// Now that the COMMIT/ROLLBACK step is over, enable post-commit callback runs
$this->forEachOpenPrimaryConnection( static function ( Database $conn ) {
$conn->setTrxEndCallbackSuppression( false );
} );
$errors = [];
$fname = __METHOD__;
// Loop until callbacks stop adding callbacks on other connections
do {
// Run any pending callbacks for each connection...
$count = 0; // callback execution attempts
$this->forEachOpenPrimaryConnection(
static function ( Database $conn ) use ( $type, &$errors, &$count ) {
if ( $conn->trxLevel() ) {
return; // retry in the next iteration, after commit() is called
}
$count += $conn->runOnTransactionIdleCallbacks( $type, $errors );
}
);
// Clear out any active transactions left over from callbacks...
$this->forEachOpenPrimaryConnection(
function ( Database $conn ) use ( &$errors, $fname ) {
if ( $conn->writesPending() ) {
// A callback from another handle wrote to this one and DBO_TRX is set
$this->queryLogger->warning( $fname . ": found writes pending." );
$fnames = implode( ', ', $conn->pendingWriteAndCallbackCallers() );
$this->queryLogger->warning(
"$fname: found writes pending ($fnames).",
$this->getConnLogContext(
$conn,
[ 'exception' => new RuntimeException() ]
)
);
} elseif ( $conn->trxLevel() ) {
// A callback from another handle read from this one and DBO_TRX is set,
// which can easily happen if there is only one DB (no replicas)
$this->queryLogger->debug( "$fname: found empty transaction." );
}
try {
$conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
} catch ( DBError $ex ) {
$errors[] = $ex;
}
}
);
} while ( $count > 0 );
$this->trxRoundStage = $oldStage;
return $errors ? $errors[0] : null;
}
public function runPrimaryTransactionListenerCallbacks( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
if ( $this->trxRoundStage === self::ROUND_COMMIT_CALLBACKS ) {
$type = IDatabase::TRIGGER_COMMIT;
} elseif ( $this->trxRoundStage === self::ROUND_ROLLBACK_CALLBACKS ) {
$type = IDatabase::TRIGGER_ROLLBACK;
} else {
throw new DBTransactionError(
null,
"Transaction should be in the callback stage (not '{$this->trxRoundStage}')"
);
}
if ( $this->ownerId === null ) {
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = ScopedCallback::newScopedIgnoreUserAbort();
}
$errors = [];
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
$this->forEachOpenPrimaryConnection(
static function ( Database $conn ) use ( $type, &$errors ) {
$conn->runTransactionListenerCallbacks( $type, $errors );
}
);
$this->trxRoundStage = self::ROUND_CURSORY;
return $errors ? $errors[0] : null;
}
public function rollbackPrimaryChanges( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
if ( $this->ownerId === null ) {
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = ScopedCallback::newScopedIgnoreUserAbort();
}
$restore = ( $this->trxRoundId !== false );
$this->trxRoundId = false;
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
$this->forEachOpenPrimaryConnection( static function ( IDatabase $conn ) use ( $fname ) {
$conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
} );
if ( $restore ) {
// Unmark handles as participating in this explicit transaction round
$this->forEachOpenPrimaryConnection( function ( Database $conn ) {
$this->undoTransactionRoundFlags( $conn );
} );
}
$this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
}
/**
* @param string|string[] $stage
* @throws DBTransactionError
*/
private function assertTransactionRoundStage( $stage ) {
$stages = (array)$stage;
if ( !in_array( $this->trxRoundStage, $stages, true ) ) {
$stageList = implode(
'/',
array_map( static function ( $v ) {
return "'$v'";
}, $stages )
);
throw new DBTransactionError(
null,
"Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
);
}
}
/**
* Assure that if this instance is owned, the caller is either the owner or is internal
*
* If an LBFactory owns the LoadBalancer, then certain methods should only called through
* that LBFactory to avoid broken contracts. Otherwise, those methods can publicly be
* called by anything. In any case, internal methods from the LoadBalancer itself should
* always be allowed.
*
* @param string $fname
* @param int|null $owner Owner ID of the caller
* @throws DBTransactionError
*/
private function assertOwnership( $fname, $owner ) {
if ( $this->ownerId !== null && $owner !== $this->ownerId && $owner !== $this->id ) {
throw new DBTransactionError(
null,
"$fname: LoadBalancer is owned by ID '{$this->ownerId}' (got '$owner')."
);
}
}
/**
* 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 Database $conn
*/
private function applyTransactionRoundFlags( Database $conn ) {
if ( $conn->getLBInfo( self::INFO_AUTOCOMMIT_ONLY ) ) {
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( $conn::LB_TRX_ROUND_ID, $this->trxRoundId );
}
}
/**
* @param Database $conn
*/
private function undoTransactionRoundFlags( Database $conn ) {
if ( $conn->getLBInfo( self::INFO_AUTOCOMMIT_ONLY ) ) {
return; // transaction rounds do not apply to these connections
}
if ( $conn->getFlag( $conn::DBO_TRX ) ) {
$conn->setLBInfo( $conn::LB_TRX_ROUND_ID, null ); // remove the round ID
}
if ( $conn->getFlag( $conn::DBO_DEFAULT ) ) {
$conn->restoreFlags( $conn::RESTORE_PRIOR );
}
}
public function flushReplicaSnapshots( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
$this->forEachOpenReplicaConnection( static function ( IDatabase $conn ) use ( $fname ) {
$conn->flushSnapshot( $fname );
} );
}
public function flushPrimarySnapshots( $fname = __METHOD__, $owner = null ) {
$this->assertOwnership( $fname, $owner );
$this->forEachOpenPrimaryConnection( static function ( IDatabase $conn ) use ( $fname ) {
$conn->flushSnapshot( $fname );
} );
}
/**
* @return string
* @since 1.32
*/
public function getTransactionRoundStage() {
return $this->trxRoundStage;
}
public function hasPrimaryConnection() {
return $this->isOpen( $this->getWriterIndex() );
}
public function hasPrimaryChanges() {
$pending = false;
$this->forEachOpenPrimaryConnection( static function ( IDatabase $conn ) use ( &$pending ) {
$pending = $pending || $conn->writesOrCallbacksPending();
} );
return $pending;
}
public function lastPrimaryChangeTimestamp() {
$lastTime = false;
$this->forEachOpenPrimaryConnection( static function ( IDatabase $conn ) use ( &$lastTime ) {
$lastTime = max( $lastTime, $conn->lastDoneWrites() );
} );
return $lastTime;
}
public function hasOrMadeRecentPrimaryChanges( $age = null ) {
$age = $age ?? $this->waitTimeout;
return ( $this->hasPrimaryChanges()
|| $this->lastPrimaryChangeTimestamp() > microtime( true ) - $age );
}
public function pendingPrimaryChangeCallers() {
$fnames = [];
$this->forEachOpenPrimaryConnection( static function ( IDatabase $conn ) use ( &$fnames ) {
$fnames = array_merge( $fnames, $conn->pendingWriteCallers() );
} );
return $fnames;
}
public function getLaggedReplicaMode( $domain = false ) {
$domain = $this->resolveDomainID( $domain );
if ( $this->laggedReplicaMode ) {
// Stay in lagged replica mode once it is observed on any domain
return true;
}
if ( $this->hasStreamingReplicaServers() ) {
// This will set "laggedReplicaMode" as needed
$this->getReaderIndex( self::GROUP_GENERIC, $domain );
}
return $this->laggedReplicaMode;
}
public function laggedReplicaUsed() {
return $this->laggedReplicaMode;
}
public function getReadOnlyReason( $domain = false ) {
$domainInstance = DatabaseDomain::newFromId( $this->resolveDomainID( $domain ) );
if ( $this->readOnlyReason !== false ) {
return $this->readOnlyReason;
} elseif ( $this->isPrimaryRunningReadOnly( $domainInstance ) ) {
return 'The primary database server is running in read-only mode.';
} elseif ( $this->getLaggedReplicaMode( $domain ) ) {
$genericIndex = $this->getExistingReaderIndex( self::GROUP_GENERIC );
return ( $genericIndex !== self::READER_INDEX_NONE )
? 'The database is read-only until replication lag decreases.'
: 'The database is read-only until a replica database server becomes reachable.';
}
return false;
}
/**
* @note This method suppresses DBError exceptions in order to avoid severe downtime
* @param IDatabase $conn Primary connection
* @param int $flags Bitfield of class CONN_* constants
* @return bool Whether the entire server or currently selected DB/schema is read-only
*/
private function isPrimaryConnectionReadOnly( IDatabase $conn, $flags = 0 ) {
// Note that table prefixes are not related to server-side read-only mode
$key = $this->srvCache->makeGlobalKey(
'rdbms-server-readonly',
$conn->getServerName(),
$conn->getDBname(),
(string)$conn->dbSchema()
);
if ( self::fieldHasBit( $flags, self::CONN_REFRESH_READ_ONLY ) ) {
// Refresh the local server cache. This is useful when the caller is
// currently in the process of updating a corresponding WANCache key.
try {
$readOnly = (int)$conn->serverIsReadOnly();
} catch ( DBError $e ) {
$readOnly = 0;
}
$this->srvCache->set( $key, $readOnly, BagOStuff::TTL_PROC_SHORT );
} else {
$readOnly = $this->srvCache->getWithSetCallback(
$key,
BagOStuff::TTL_PROC_SHORT,
static function () use ( $conn ) {
try {
$readOnly = (int)$conn->serverIsReadOnly();
} catch ( DBError $e ) {
$readOnly = 0;
}
return $readOnly;
}
);
}
return (bool)$readOnly;
}
/**
* @note This method suppresses DBError exceptions in order to avoid severe downtime
* @param DatabaseDomain $domain
* @return bool Whether the entire primary DB server or the local domain DB is read-only
*/
private function isPrimaryRunningReadOnly( DatabaseDomain $domain ) {
// Context will often be HTTP GET/HEAD; heavily cache the results
return (bool)$this->wanCache->getWithSetCallback(
// Note that table prefixes are not related to server-side read-only mode
$this->wanCache->makeGlobalKey(
'rdbms-server-readonly',
$this->getPrimaryServerName(),
$domain->getDatabase(),
(string)$domain->getSchema()
),
self::TTL_CACHE_READONLY,
function () use ( $domain ) {
$scope = $this->trxProfiler->silenceForScope();
$index = $this->getWriterIndex();
// Refresh the local server cache as well. This is done in order to avoid
// backfilling the WANCache with data that is already significantly stale
$flags = self::CONN_SILENCE_ERRORS | self::CONN_REFRESH_READ_ONLY;
$conn = $this->getServerConnection( $index, $domain->getId(), $flags );
if ( $conn ) {
try {
$readOnly = (int)$this->isPrimaryConnectionReadOnly( $conn );
} catch ( DBError $e ) {
$readOnly = 0;
}
$this->reuseConnection( $conn );
} else {
$readOnly = 0;
}
ScopedCallback::consume( $scope );
return $readOnly;
},
[
'busyValue' => 0,
'pcTTL' => WANObjectCache::TTL_PROC_LONG
]
);
}
public function pingAll() {
$success = true;
$this->forEachOpenConnection( static 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 ) {
$callback( $conn, ...$params );
}
}
}
}
public function forEachOpenPrimaryConnection( $callback, array $params = [] ) {
$primaryIndex = $this->getWriterIndex();
foreach ( $this->conns as $connsByServer ) {
if ( isset( $connsByServer[$primaryIndex] ) ) {
/** @var IDatabase $conn */
foreach ( $connsByServer[$primaryIndex] as $conn ) {
$callback( $conn, ...$params );
}
}
}
}
private function forEachOpenReplicaConnection( $callback ) {
foreach ( $this->conns as $connsByServer ) {
foreach ( $connsByServer as $i => $serverConns ) {
if ( $i === $this->getWriterIndex() ) {
continue; // skip primary DB
}
foreach ( $serverConns as $conn ) {
$callback( $conn );
}
}
}
}
/**
* @return int
*/
private function getCurrentConnectionCount() {
$count = 0;
foreach ( $this->conns as $connsByServer ) {
foreach ( $connsByServer as $serverConns ) {
$count += count( $serverConns );
}
}
return $count;
}
public function getMaxLag( $domain = false ) {
$domain = $this->resolveDomainID( $domain );
$host = '';
$maxLag = -1;
$maxIndex = 0;
if ( $this->hasReplicaServers() ) {
$lagTimes = $this->getLagTimes( $domain );
foreach ( $lagTimes as $i => $lag ) {
if ( $this->groupLoads[self::GROUP_GENERIC][$i] > 0 && $lag > $maxLag ) {
$maxLag = $lag;
$host = $this->getServerInfoStrict( $i, 'host' );
$maxIndex = $i;
}
}
}
return [ $host, $maxLag, $maxIndex ];
}
public function getLagTimes( $domain = false ) {
$domain = $this->resolveDomainID( $domain );
if ( !$this->hasReplicaServers() ) {
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 waitForPrimaryPos( IDatabase $conn, $pos = false, $timeout = null ) {
$timeout = max( 1, $timeout ?: $this->waitTimeout );
if ( $conn->getLBInfo( self::INFO_SERVER_INDEX ) === $this->getWriterIndex() ) {
return true; // not a replica DB server
}
if ( !$pos ) {
// Get the current primary DB position, opening a connection only if needed
$this->replLogger->debug( __METHOD__ . ': no position passed; using current' );
$index = $this->getWriterIndex();
$flags = self::CONN_SILENCE_ERRORS;
$primaryConn = $this->getAnyOpenConnection( $index, $flags );
if ( $primaryConn ) {
$pos = $primaryConn->getPrimaryPos();
} else {
$primaryConn = $this->getServerConnection( $index, self::DOMAIN_ANY, $flags );
if ( !$primaryConn ) {
throw new DBReplicationWaitError(
null,
"Could not obtain a primary database connection to get the position"
);
}
$pos = $primaryConn->getPrimaryPos();
$this->closeConnection( $primaryConn );
}
}
if ( $pos instanceof DBPrimaryPos ) {
$this->replLogger->debug( __METHOD__ . ': waiting' );
$result = $conn->primaryPosWait( $pos, $timeout );
$ok = ( $result !== null && $result != -1 );
if ( $ok ) {
$this->replLogger->debug( __METHOD__ . ': done waiting (success)' );
} else {
$this->replLogger->debug( __METHOD__ . ': done waiting (failure)' );
}
} else {
$ok = false; // something is misconfigured
$this->replLogger->error(
__METHOD__ . ': could not get primary pos for {db_server}',
$this->getConnLogContext( $conn, [ 'exception' => new RuntimeException() ] )
);
}
return $ok;
}
public function setTransactionListener( $name, callable $callback = null ) {
if ( $callback ) {
$this->trxRecurringCallbacks[$name] = $callback;
} else {
unset( $this->trxRecurringCallbacks[$name] );
}
$this->forEachOpenPrimaryConnection(
static 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 setDomainAliases( array $aliases ) {
$this->domainAliases = $aliases;
}
public function setLocalDomainPrefix( $prefix ) {
// Find connections to explicit foreign domains still marked as in-use...
$domainsInUse = [];
$this->forEachOpenConnection( static 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( self::INFO_FOREIGN_REF_COUNT ) > 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->setLocalDomain( new DatabaseDomain(
$this->localDomain->getDatabase(),
$this->localDomain->getSchema(),
$prefix
) );
// Update the prefix for all local connections...
$this->forEachOpenConnection( static function ( IDatabase $conn ) use ( $prefix ) {
if ( !$conn->getLBInfo( self::INFO_FORIEGN ) ) {
$conn->tablePrefix( $prefix );
}
} );
}
public function redefineLocalDomain( $domain ) {
$this->closeAll( __METHOD__, $this->id );
$this->setLocalDomain( DatabaseDomain::newFromId( $domain ) );
}
public function setTempTablesOnlyMode( $value, $domain ) {
$old = $this->tempTablesOnlyMode[$domain] ?? false;
if ( $value ) {
$this->tempTablesOnlyMode[$domain] = true;
} else {
unset( $this->tempTablesOnlyMode[$domain] );
}
return $old;
}
/**
* @param DatabaseDomain $domain
*/
private function setLocalDomain( DatabaseDomain $domain ) {
$this->localDomain = $domain;
}
/**
* @param int $i Server index
* @param string|null $field Server index field [optional]
* @return array|mixed
* @throws InvalidArgumentException
*/
private function getServerInfoStrict( $i, $field = null ) {
if ( !isset( $this->servers[$i] ) || !is_array( $this->servers[$i] ) ) {
throw new InvalidArgumentException( "No server with index '$i'" );
}
if ( $field !== null ) {
if ( !array_key_exists( $field, $this->servers[$i] ) ) {
throw new InvalidArgumentException( "No field '$field' in server index '$i'" );
}
return $this->servers[$i][$field];
}
return $this->servers[$i];
}
/**
* @return string Name of the primary DB server of the relevant DB cluster (e.g. "db1052")
*/
private function getPrimaryServerName() {
return $this->getServerName( $this->getWriterIndex() );
}
/**
* @param int $flags A bitfield of flags
* @param int $bit Bit flag constant
* @return bool Whether the bit field has the specified bit flag set
*/
private function fieldHasBit( int $flags, int $bit ) {
return ( ( $flags & $bit ) === $bit );
}
/**
* Create a log context to pass to PSR-3 logger functions.
*
* @param IDatabase $conn
* @param array $extras Additional data to add to context
* @return array
*/
protected function getConnLogContext( IDatabase $conn, array $extras = [] ) {
return array_merge(
[
'db_server' => $conn->getServerName(),
'db_domain' => $conn->getDomainID()
],
$extras
);
}
public function __destruct() {
// Avoid connection leaks
$this->disable( __METHOD__, $this->ownerId );
}
}
/**
* @deprecated since 1.29
*/
class_alias( LoadBalancer::class, 'LoadBalancer' );