Current File : //www/varak.net/wiki.varak.net/includes/libs/rdbms/loadbalancer/LoadBalancer.php
<?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 UnexpectedValueException;
use InvalidArgumentException;
use RuntimeException;
use Exception;
/**
* Database connection, tracking, load balancing, and transaction manager for a cluster
*
* @ingroup Database
*/
class LoadBalancer implements ILoadBalancer {
/** @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 */
private $profiler;
/** @var TransactionProfiler */
private $trxProfiler;
/** @var LoggerInterface */
private $replLogger;
/** @var LoggerInterface */
private $connLogger;
/** @var LoggerInterface */
private $queryLogger;
/** @var LoggerInterface */
private $perfLogger;
/** @var callable Exception logger */
private $errorLogger;
/** @var callable Deprecation logger */
private $deprecationLogger;
/** @var DatabaseDomain Local Domain ID and default for selectDB() calls */
private $localDomain;
/** @var Database[][][] Map of (connection category => server index => IDatabase[]) */
private $conns;
/** @var array[] Map of (server index => server config array) */
private $servers;
/** @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 string Alternate ID string for the domain instead of DatabaseDomain::getId() */
private $localDomainIdAlias;
/** @var int */
private $maxLag = self::MAX_LAG_DEFAULT;
/** @var string Current server name */
private $hostname;
/** @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 array[] Map of (name => callable) */
private $trxRecurringCallbacks = [];
/** @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 bool */
private $disabled = false;
/** @var bool Whether any connection has been attempted yet */
private $connectionAttempted = false;
/** @var string|bool String if a requested DBO_TRX transaction round is active */
private $trxRoundId = false;
/** @var string Stage of the current transaction round in the transaction round life-cycle */
private $trxRoundStage = self::ROUND_CURSORY;
/** @var string|null */
private $defaultGroup = null;
/** @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';
/** @var string Transaction round, explicit or implicit, has not finished writing */
const ROUND_CURSORY = 'cursory';
/** @var string Transaction round writes are complete and ready for pre-commit checks */
const ROUND_FINALIZED = 'finalized';
/** @var string Transaction round passed final pre-commit checks */
const ROUND_APPROVED = 'approved';
/** @var string Transaction round was committed and post-commit callbacks must be run */
const ROUND_COMMIT_CALLBACKS = 'commit-callbacks';
/** @var string Transaction round was rolled back and post-rollback callbacks must be run */
const ROUND_ROLLBACK_CALLBACKS = 'rollback-callbacks';
/** @var string Transaction round encountered an error */
const ROUND_ERROR = 'error';
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 = $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 = $params['profiler'] ?? null;
if ( isset( $params['trxProfiler'] ) ) {
$this->trxProfiler = $params['trxProfiler'];
} else {
$this->trxProfiler = new TransactionProfiler();
}
$this->errorLogger = $params['errorLogger'] ?? function ( Exception $e ) {
trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
};
$this->deprecationLogger = $params['deprecationLogger'] ?? function ( $msg ) {
trigger_error( $msg, E_USER_DEPRECATED );
};
foreach ( [ 'replLogger', 'connLogger', 'queryLogger', 'perfLogger' ] as $key ) {
$this->$key = $params[$key] ?? new NullLogger();
}
$this->hostname = $params['hostname'] ?? ( gethostname() ?: 'unknown' );
$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;
}
}
$this->defaultGroup = $params['defaultGroup'] ?? null;
}
public function getLocalDomainID() {
return $this->localDomain->getId();
}
public function resolveDomainID( $domain ) {
return ( $domain !== false ) ? (string)$domain : $this->getLocalDomainID();
}
/**
* 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 = $this->servers[$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->info(
__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|null $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.' );
}
}
// Check one "group" per default: the generic pool
$defaultGroups = $this->defaultGroup ? [ $this->defaultGroup ] : [ false ];
$groups = ( $groups === false || $groups === [] )
? $defaultGroups
: (array)$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 = $this->resolveDomainID( $domain );
return new DBConnRef( $this, $this->getConnection( $db, $groups, $domain, $flags ) );
}
public function getLazyConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
$domain = $this->resolveDomainID( $domain );
return new DBConnRef( $this, [ $db, $groups, $domain, $flags ] );
}
public function getMaintenanceConnectionRef( $db, $groups = [], $domain = false, $flags = 0 ) {
$domain = $this->resolveDomainID( $domain );
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;
( $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
$conn = $this->openLocalConnection( $i, $flags );
}
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 ) {
if ( $conn->trxLevel() ) { // sanity
throw new DBUnexpectedError(
$conn,
__METHOD__ . ': CONN_TRX_AUTOCOMMIT handle has a transaction.'
);
}
$conn->clearFlag( $conn::DBO_TRX ); // auto-commit mode
}
return $conn;
}
/**
* 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 Server index
* @param int $flags Class CONN_* constant bitfield
* @return Database
*/
private function openLocalConnection( $i, $flags = 0 ) {
$autoCommit = ( ( $flags & self::CONN_TRX_AUTOCOMMIT ) == self::CONN_TRX_AUTOCOMMIT );
$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;
$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;
}
}
// Final sanity check to make sure 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 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
*/
private function openForeignConnection( $i, $domain, $flags = 0 ) {
$domainInstance = DatabaseDomain::newFromId( $domain );
$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;
}
/** @var Database $conn */
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 ( $domainInstance->getDatabase() !== null ) {
$conn->selectDomain( $domainInstance );
} else {
// Stay on the current database, but update the schema/prefix
$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" );
} 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 {
// 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" );
}
}
if ( $conn instanceof IDatabase ) {
// Final sanity check to make sure the right domain is selected
if ( !$domainInstance->isCompatible( $conn->getDomainID() ) ) {
throw new UnexpectedValueException(
"Got connection to '{$conn->getDomainID()}', but expected '$domain'." );
}
// Increment reference count
$refCount = $conn->getLBInfo( 'foreignPoolRefCount' );
$conn->setLBInfo( 'foreignPoolRefCount', $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
* @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 $domain Domain the connection is for, possibly unspecified
* @return Database
* @throws DBAccessError
* @throws InvalidArgumentException
*/
protected function reallyOpenConnection( array $server, DatabaseDomain $domain ) {
if ( $this->disabled ) {
throw new DBAccessError();
}
if ( $domain->getDatabase() === null ) {
// The database domain does not specify a DB name and some database systems require a
// valid DB specified on connection. The $server configuration array contains a default
// DB name to use for connections in such cases.
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'] = $domain->getDatabase();
}
if ( $domain->getSchema() !== null ) {
$server['schema'] = $domain->getSchema();
}
// It is always possible to connect with any prefix, even the empty string
$server['tablePrefix'] = $domain->getTablePrefix();
// 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'] = $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
);
throw new DBConnectionError( $conn, "{$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 $this->servers[$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() {
$fname = __METHOD__;
$this->forEachOpenConnection( function ( IDatabase $conn ) use ( $fname ) {
$host = $conn->getServer();
$this->connLogger->debug(
$fname . ": closing connection to database '$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__ ) {
$this->commitMasterChanges( $fname );
$this->flushMasterSnapshots( $fname );
$this->flushReplicaSnapshots( $fname );
}
public function finalizeMasterChanges() {
$this->assertTransactionRoundStage( [ self::ROUND_CURSORY, self::ROUND_FINALIZED ] );
$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->forEachOpenMasterConnection( 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->forEachOpenMasterConnection( function ( Database $conn ) {
$conn->setTrxEndCallbackSuppression( true );
} );
$this->trxRoundStage = self::ROUND_FINALIZED;
return $total;
}
public function approveMasterChanges( array $options ) {
$this->assertTransactionRoundStage( self::ROUND_FINALIZED );
$limit = $options['maxWriteDuration'] ?? 0;
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
$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).
$conn->assertNoOpenTransactions();
// 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."
);
}
} );
$this->trxRoundStage = self::ROUND_APPROVED;
}
public function beginMasterChanges( $fname = __METHOD__ ) {
if ( $this->trxRoundId !== false ) {
throw new DBTransactionError(
null,
"$fname: Transaction round '{$this->trxRoundId}' already started."
);
}
$this->assertTransactionRoundStage( self::ROUND_CURSORY );
// Clear any empty transactions (no writes/callbacks) from the implicit round
$this->flushMasterSnapshots( $fname );
$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->forEachOpenMasterConnection( function ( Database $conn ) {
$this->applyTransactionRoundFlags( $conn );
} );
$this->trxRoundStage = self::ROUND_CURSORY;
}
public function commitMasterChanges( $fname = __METHOD__ ) {
$this->assertTransactionRoundStage( self::ROUND_APPROVED );
$failures = [];
/** @noinspection PhpUnusedLocalVariableInspection */
$scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
$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 finalizeMasterChanges().
$this->forEachOpenMasterConnection(
function ( IDatabase $conn ) use ( $fname, &$failures ) {
try {
$conn->commit( $fname, $conn::FLUSHING_ALL_PEERS );
} catch ( DBError $e ) {
( $this->errorLogger )( $e );
$failures[] = "{$conn->getServer()}: {$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->forEachOpenMasterConnection( function ( Database $conn ) {
$this->undoTransactionRoundFlags( $conn );
} );
}
$this->trxRoundStage = self::ROUND_COMMIT_CALLBACKS;
}
public function runMasterTransactionIdleCallbacks() {
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}')"
);
}
$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->forEachOpenMasterConnection( function ( Database $conn ) {
$conn->setTrxEndCallbackSuppression( false );
} );
$e = null; // first exception
$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->forEachOpenMasterConnection(
function ( Database $conn ) use ( $type, &$e, &$count ) {
if ( $conn->trxLevel() ) {
return; // retry in the next iteration, after commit() is called
}
try {
$count += $conn->runOnTransactionIdleCallbacks( $type );
} catch ( Exception $ex ) {
$e = $e ?: $ex;
}
}
);
// Clear out any active transactions left over from callbacks...
$this->forEachOpenMasterConnection( function ( Database $conn ) use ( &$e, $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).",
[
'db_server' => $conn->getServer(),
'db_name' => $conn->getDBname()
]
);
} 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 ( Exception $ex ) {
$e = $e ?: $ex;
}
} );
} while ( $count > 0 );
$this->trxRoundStage = $oldStage;
return $e;
}
public function runMasterTransactionListenerCallbacks() {
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}')"
);
}
$e = null;
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
$this->forEachOpenMasterConnection( function ( Database $conn ) use ( $type, &$e ) {
try {
$conn->runTransactionListenerCallbacks( $type );
} catch ( Exception $ex ) {
$e = $e ?: $ex;
}
} );
$this->trxRoundStage = self::ROUND_CURSORY;
return $e;
}
public function rollbackMasterChanges( $fname = __METHOD__ ) {
$restore = ( $this->trxRoundId !== false );
$this->trxRoundId = false;
$this->trxRoundStage = self::ROUND_ERROR; // "failed" until proven otherwise
$this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
$conn->rollback( $fname, $conn::FLUSHING_ALL_PEERS );
} );
if ( $restore ) {
// Unmark handles as participating in this explicit transaction round
$this->forEachOpenMasterConnection( function ( Database $conn ) {
$this->undoTransactionRoundFlags( $conn );
} );
}
$this->trxRoundStage = self::ROUND_ROLLBACK_CALLBACKS;
}
/**
* @param string|string[] $stage
*/
private function assertTransactionRoundStage( $stage ) {
$stages = (array)$stage;
if ( !in_array( $this->trxRoundStage, $stages, true ) ) {
$stageList = implode(
'/',
array_map( function ( $v ) {
return "'$v'";
}, $stages )
);
throw new DBTransactionError(
null,
"Transaction round stage must be $stageList (not '{$this->trxRoundStage}')"
);
}
}
/**
* 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( '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 Database $conn
*/
private function undoTransactionRoundFlags( Database $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 ) use ( $fname ) {
$conn->flushSnapshot( $fname );
} );
}
public function flushMasterSnapshots( $fname = __METHOD__ ) {
$this->forEachOpenMasterConnection( function ( IDatabase $conn ) use ( $fname ) {
$conn->flushSnapshot( $fname );
} );
}
/**
* @return string
* @since 1.32
*/
public function getTransactionRoundStage() {
return $this->trxRoundStage;
}
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;
}
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 ) {
$callback( $conn, ...$params );
}
}
}
}
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 ) {
$callback( $conn, ...$params );
}
}
}
}
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 ) {
$callback( $conn, ...$params );
}
}
}
}
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)." );
}
$this->setLocalDomain( new DatabaseDomain(
$this->localDomain->getDatabase(),
$this->localDomain->getSchema(),
$prefix
) );
// Update the prefix for all local connections...
$this->forEachOpenConnection( function ( IDatabase $db ) use ( $prefix ) {
if ( !$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();
}
}
/**
* @deprecated since 1.29
*/
class_alias( LoadBalancer::class, 'LoadBalancer' );
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