rdbms: make getMasterPos() ignore GTIDs outside of gtid_domain_id

* Filter out GTIDs with a domain that is not the one binlog
  events would be written to if the Database handle was given
  write queries. Likewise for the MariaDB server_id component.
* Also improve MySQL GTID support to better match that of MariaDB.
  This covers position retrieval, replication waiting, and ranges
  in GTIDs (which are almost always present).
* Make some MySQLMasterPos variables private by making use of
  accesors instead.
* Store the gtids array keyed by domain ID for convenience.
* Clean up dynamic call to static method.

Change-Id: Ic6ab517bc8f200c968ff892ade69ad1b9394ab21

includes/libs/rdbms/database/DatabaseMysqlBase.php

@@ -70,6 +70,9 @@ abstract class DatabaseMysqlBase extends Database {
 	/** @var stdClass|null */
 	private $replicationInfoRow = null;
 
+	// Cache getServerId() for 24 hours
+	const SERVER_ID_CACHE_TTL = 86400;
+
 	/**
 	 * Additional $params include:
 	 *   - lagDetectionMethod : set to one of (Seconds_Behind_Master,pt-heartbeat).
@@ -902,18 +905,23 @@ abstract class DatabaseMysqlBase extends Database {
 			}
 			// Wait on the GTID set (MariaDB only)
 			$gtidArg = $this->addQuotes( implode( ',', $gtidsWait ) );
-			$res = $this->doQuery( "SELECT MASTER_GTID_WAIT($gtidArg, $timeout)" );
+			if ( strpos( $gtidArg, ':' ) !== false ) {
+				// MySQL GTIDs, e.g "source_id:transaction_id"
+				$res = $this->doQuery( "SELECT WAIT_FOR_EXECUTED_GTID_SET($gtidArg, $timeout)" );
+			} else {
+				// MariaDB GTIDs, e.g."domain:server:sequence"
+				$res = $this->doQuery( "SELECT MASTER_GTID_WAIT($gtidArg, $timeout)" );
+			}
 		} else {
 			// Wait on the binlog coordinates
 			$encFile = $this->addQuotes( $pos->getLogFile() );
-			$encPos = intval( $pos->pos[1] );
+			$encPos = intval( $pos->getLogPosition()[$pos::CORD_EVENT] );
 			$res = $this->doQuery( "SELECT MASTER_POS_WAIT($encFile, $encPos, $timeout)" );
 		}
 
 		$row = $res ? $this->fetchRow( $res ) : false;
 		if ( !$row ) {
-			throw new DBExpectedError( $this,
+			throw new DBExpectedError( $this, "Replication wait failed: {$this->lastError()}" );
-				"MASTER_POS_WAIT() or MASTER_GTID_WAIT() failed: {$this->lastError()}" );
 		}
 
 		// Result can be NULL (error), -1 (timeout), or 0+ per the MySQL manual
@@ -945,21 +953,23 @@ abstract class DatabaseMysqlBase extends Database {
 	 * @return MySQLMasterPos|bool
 	 */
 	public function getReplicaPos() {
-		$now = microtime( true );
+		$now = microtime( true ); // as-of-time *before* fetching GTID variables
 
-		if ( $this->useGTIDs ) {
+		if ( $this->useGTIDs() ) {
-			$res = $this->query( "SELECT @@global.gtid_slave_pos AS Value", __METHOD__ );
+			// Try to use GTIDs, fallbacking to binlog positions if not possible
-			$gtidRow = $this->fetchObject( $res );
+			$data = $this->getServerGTIDs( __METHOD__ );
-			if ( $gtidRow && strlen( $gtidRow->Value ) ) {
+			// Use gtid_current_pos for MariaDB and gtid_executed for MySQL
-				return new MySQLMasterPos( $gtidRow->Value, $now );
+			foreach ( [ 'gtid_current_pos', 'gtid_executed' ] as $name ) {
+				if ( isset( $data[$name] ) && strlen( $data[$name] ) ) {
+					return new MySQLMasterPos( $data[$name], $now );
+				}
 			}
 		}
 
-		$res = $this->query( 'SHOW SLAVE STATUS', __METHOD__ );
+		$data = $this->getServerRoleStatus( 'SLAVE', __METHOD__ );
-		$row = $this->fetchObject( $res );
+		if ( $data && strlen( $data['Relay_Master_Log_File'] ) ) {
-		if ( $row && strlen( $row->Relay_Master_Log_File ) ) {
 			return new MySQLMasterPos(
-				"{$row->Relay_Master_Log_File}/{$row->Exec_Master_Log_Pos}",
+				"{$data['Relay_Master_Log_File']}/{$data['Exec_Master_Log_Pos']}",
 				$now
 			);
 		}
@@ -973,23 +983,97 @@ abstract class DatabaseMysqlBase extends Database {
 	 * @return MySQLMasterPos|bool
 	 */
 	public function getMasterPos() {
-		$now = microtime( true );
+		$now = microtime( true ); // as-of-time *before* fetching GTID variables
 
-		if ( $this->useGTIDs ) {
+		$pos = false;
-			$res = $this->query( "SELECT @@global.gtid_binlog_pos AS Value", __METHOD__ );
+		if ( $this->useGTIDs() ) {
-			$gtidRow = $this->fetchObject( $res );
+			// Try to use GTIDs, fallbacking to binlog positions if not possible
-			if ( $gtidRow && strlen( $gtidRow->Value ) ) {
+			$data = $this->getServerGTIDs( __METHOD__ );
-				return new MySQLMasterPos( $gtidRow->Value, $now );
+			// Use gtid_current_pos for MariaDB and gtid_executed for MySQL
+			foreach ( [ 'gtid_current_pos', 'gtid_executed' ] as $name ) {
+				if ( isset( $data[$name] ) && strlen( $data[$name] ) ) {
+					$pos = new MySQLMasterPos( $data[$name], $now );
+					break;
+				}
+			}
+			// Filter domains that are inactive or not relevant to the session
+			if ( $pos ) {
+				$pos->setActiveOriginServerId( $this->getServerId() );
+				$pos->setActiveOriginServerUUID( $this->getServerUUID() );
+				if ( isset( $data['gtid_domain_id'] ) ) {
+					$pos->setActiveDomain( $data['gtid_domain_id'] );
+				}
 			}
 		}
 
-		$res = $this->query( 'SHOW MASTER STATUS', __METHOD__ );
+		if ( !$pos ) {
-		$row = $this->fetchObject( $res );
+			$data = $this->getServerRoleStatus( 'MASTER', __METHOD__ );
-		if ( $row && strlen( $row->File ) ) {
+			if ( $data && strlen( $data['File'] ) ) {
-			return new MySQLMasterPos( "{$row->File}/{$row->Position}", $now );
+				$pos = new MySQLMasterPos( "{$data['File']}/{$data['Position']}", $now );
+			}
 		}
 
-		return false;
+		return $pos;
+	}
+
+	/**
+	 * @return int
+	 * @throws DBQueryError If the variable doesn't exist for some reason
+	 */
+	protected function getServerId() {
+		return $this->srvCache->getWithSetCallback(
+			$this->srvCache->makeGlobalKey( 'mysql-server-id', $this->getServer() ),
+			self::SERVER_ID_CACHE_TTL,
+			function () {
+				$res = $this->query( "SELECT @@server_id AS id", __METHOD__ );
+				return intval( $this->fetchObject( $res )->id );
+			}
+		);
+	}
+
+	/**
+	 * @return string|null
+	 */
+	protected function getServerUUID() {
+		return $this->srvCache->getWithSetCallback(
+			$this->srvCache->makeGlobalKey( 'mysql-server-uuid', $this->getServer() ),
+			self::SERVER_ID_CACHE_TTL,
+			function () {
+				$res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'server_uuid'" );
+				$row = $this->fetchObject( $res );
+
+				return $row ? $row->Value : null;
+			}
+		);
+	}
+
+	/**
+	 * @param string $fname
+	 * @return string[]
+	 */
+	protected function getServerGTIDs( $fname = __METHOD__ ) {
+		$map = [];
+		// Get global-only variables like gtid_executed
+		$res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'gtid_%'", $fname );
+		foreach ( $res as $row ) {
+			$map[$row->Variable_name] = $row->Value;
+		}
+		// Get session-specific (e.g. gtid_domain_id since that is were writes will log)
+		$res = $this->query( "SHOW SESSION VARIABLES LIKE 'gtid_%'", $fname );
+		foreach ( $res as $row ) {
+			$map[$row->Variable_name] = $row->Value;
+		}
+
+		return $map;
+	}
+
+	/**
+	 * @param string $role One of "MASTER"/"SLAVE"
+	 * @param string $fname
+	 * @return string[] Latest available server status row
+	 */
+	protected function getServerRoleStatus( $role, $fname = __METHOD__ ) {
+		return $this->query( "SHOW $role STATUS", $fname )->fetchRow() ?: [];
 	}
 
 	public function serverIsReadOnly() {
@@ -1434,6 +1518,12 @@ abstract class DatabaseMysqlBase extends Database {
 		return 'CAST( ' . $field . ' AS SIGNED )';
 	}
 
+	/*
+	 * @return bool Whether GTID support is used (mockable for testing)
+	 */
+	protected function useGTIDs() {
+		return $this->useGTIDs;
+	}
 }
 
 class_alias( DatabaseMysqlBase::class, 'DatabaseMysqlBase' );

includes/libs/rdbms/database/position/MySQLMasterPos.php

@@ -12,16 +12,36 @@ use UnexpectedValueException;
  *  - Binlog-based usage assumes single-source replication and non-hierarchical replication.
  *  - GTID-based usage allows getting/syncing with multi-source replication. It is assumed
  *    that GTID sets are complete (e.g. include all domains on the server).
+ *
+ * @see https://mariadb.com/kb/en/library/gtid/
+ * @see https://dev.mysql.com/doc/refman/5.6/en/replication-gtids-concepts.html
  */
 class MySQLMasterPos implements DBMasterPos {
-	/** @var string|null Binlog file base name */
+	/** @var int One of (BINARY_LOG, GTID_MYSQL, GTID_MARIA) */
-	public $binlog;
+	private $style;
-	/** @var int[]|null Binglog file position tuple */
+	/** @var string|null Base name of all Binary Log files */
-	public $pos;
+	private $binLog;
-	/** @var string[] GTID list */
+	/** @var int[]|null Binary Log position tuple (index number, event number) */
-	public $gtids = [];
+	private $logPos;
+	/** @var string[] Map of (server_uuid/gtid_domain_id => GTID) */
+	private $gtids = [];
+	/** @var int|null Active GTID domain ID */
+	private $activeDomain;
+	/** @var int|null ID of the server were DB writes originate */
+	private $activeServerId;
+	/** @var string|null UUID of the server were DB writes originate */
+	private $activeServerUUID;
 	/** @var float UNIX timestamp */
-	public $asOfTime = 0.0;
+	private $asOfTime = 0.0;
+
+	const BINARY_LOG = 'binary-log';
+	const GTID_MARIA = 'gtid-maria';
+	const GTID_MYSQL = 'gtid-mysql';
+
+	/** @var int Key name of the binary log index number of a position tuple */
+	const CORD_INDEX = 0;
+	/** @var int Key name of the binary log event number of a position tuple */
+	const CORD_EVENT = 1;
 
 	/**
 	 * @param string $position One of (comma separated GTID list, <binlog file>/<integer>)
@@ -38,18 +58,38 @@ class MySQLMasterPos implements DBMasterPos {
 	protected function init( $position, $asOfTime ) {
 		$m = [];
 		if ( preg_match( '!^(.+)\.(\d+)/(\d+)$!', $position, $m ) ) {
-			$this->binlog = $m[1]; // ideally something like host name
+			$this->binLog = $m[1]; // ideally something like host name
-			$this->pos = [ (int)$m[2], (int)$m[3] ];
+			$this->logPos = [ self::CORD_INDEX => (int)$m[2], self::CORD_EVENT => (int)$m[3] ];
+			$this->style = self::BINARY_LOG;
 		} else {
 			$gtids = array_filter( array_map( 'trim', explode( ',', $position ) ) );
 			foreach ( $gtids as $gtid ) {
-				if ( !self::parseGTID( $gtid ) ) {
+				$components = self::parseGTID( $gtid );
+				if ( !$components ) {
 					throw new InvalidArgumentException( "Invalid GTID '$gtid'." );
 				}
-				$this->gtids[] = $gtid;
+
+				list( $domain, $pos ) = $components;
+				if ( isset( $this->gtids[$domain] ) ) {
+					// For MySQL, handle the case where some past issue caused a gap in the
+					// executed GTID set, e.g. [last_purged+1,N-1] and [N+1,N+2+K]. Ignore the
+					// gap by using the GTID with the highest ending sequence number.
+					list( , $otherPos ) = self::parseGTID( $this->gtids[$domain] );
+					if ( $pos > $otherPos ) {
+						$this->gtids[$domain] = $gtid;
+					}
+				} else {
+					$this->gtids[$domain] = $gtid;
+				}
+
+				if ( is_int( $domain ) ) {
+					$this->style = self::GTID_MARIA; // gtid_domain_id
+				} else {
+					$this->style = self::GTID_MYSQL; // server_uuid
+				}
 			}
 			if ( !$this->gtids ) {
-				throw new InvalidArgumentException( "Got empty GTID set." );
+				throw new InvalidArgumentException( "GTID set cannot be empty." );
 			}
 		}
 
@@ -66,8 +106,8 @@ class MySQLMasterPos implements DBMasterPos {
 		}
 
 		// Prefer GTID comparisons, which work with multi-tier replication
-		$thisPosByDomain = $this->getGtidCoordinates();
+		$thisPosByDomain = $this->getActiveGtidCoordinates();
-		$thatPosByDomain = $pos->getGtidCoordinates();
+		$thatPosByDomain = $pos->getActiveGtidCoordinates();
 		if ( $thisPosByDomain && $thatPosByDomain ) {
 			$comparisons = [];
 			// Check that this has positions reaching those in $pos for all domains in common
@@ -100,8 +140,8 @@ class MySQLMasterPos implements DBMasterPos {
 		}
 
 		// Prefer GTID comparisons, which work with multi-tier replication
-		$thisPosDomains = array_keys( $this->getGtidCoordinates() );
+		$thisPosDomains = array_keys( $this->getActiveGtidCoordinates() );
-		$thatPosDomains = array_keys( $pos->getGtidCoordinates() );
+		$thatPosDomains = array_keys( $pos->getActiveGtidCoordinates() );
 		if ( $thisPosDomains && $thatPosDomains ) {
 			// Check that $this has a GTID for at least one domain also in $pos; due to MariaDB
 			// quirks, prior master switch-overs may result in inactive garbage GTIDs that cannot
@@ -118,74 +158,119 @@ class MySQLMasterPos implements DBMasterPos {
 	}
 
 	/**
-	 * @return string|null
+	 * @return string|null Base name of binary log files
+	 * @since 1.31
 	 */
-	public function getLogFile() {
+	public function getLogName() {
-		return $this->gtids ? null : "{$this->binlog}.{$this->pos[0]}";
+		return $this->gtids ? null : $this->binLog;
 	}
 
 	/**
-	 * @return string[]
+	 * @return int[]|null Tuple of (binary log file number, event number)
+	 * @since 1.31
+	 */
+	public function getLogPosition() {
+		return $this->gtids ? null : $this->logPos;
+	}
+
+	/**
+	 * @return string|null Name of the binary log file for this position
+	 * @since 1.31
+	 */
+	public function getLogFile() {
+		return $this->gtids ? null : "{$this->binLog}.{$this->logPos[self::CORD_INDEX]}";
+	}
+
+	/**
+	 * @return string[] Map of (server_uuid/gtid_domain_id => GTID)
+	 * @since 1.31
 	 */
 	public function getGTIDs() {
 		return $this->gtids;
 	}
 
 	/**
-	 * @return string GTID set or <binlog file>/<position> (e.g db1034-bin.000976/843431247)
+	 * @param int|null $id @@gtid_domain_id of the active replication stream
+	 * @since 1.31
 	 */
-	public function __toString() {
+	public function setActiveDomain( $id ) {
-		return $this->gtids
+		$this->activeDomain = (int)$id;
-			? implode( ',', $this->gtids )
+	}
-			: $this->getLogFile() . "/{$this->pos[1]}";
+
+	/**
+	 * @param int|null $id @@server_id of the server were writes originate
+	 * @since 1.31
+	 */
+	public function setActiveOriginServerId( $id ) {
+		$this->activeServerId = (int)$id;
+	}
+
+	/**
+	 * @param string|null $id @@server_uuid of the server were writes originate
+	 * @since 1.31
+	 */
+	public function setActiveOriginServerUUID( $id ) {
+		$this->activeServerUUID = $id;
 	}
 
 	/**
 	 * @param MySQLMasterPos $pos
 	 * @param MySQLMasterPos $refPos
 	 * @return string[] List of GTIDs from $pos that have domains in $refPos
+	 * @since 1.31
 	 */
 	public static function getCommonDomainGTIDs( MySQLMasterPos $pos, MySQLMasterPos $refPos ) {
-		$gtidsCommon = [];
+		return array_values(
-
+			array_intersect_key( $pos->gtids, $refPos->getActiveGtidCoordinates() )
-		$relevantDomains = $refPos->getGtidCoordinates(); // (domain => unused)
+		);
-		foreach ( $pos->gtids as $gtid ) {
-			list( $domain ) = self::parseGTID( $gtid );
-			if ( isset( $relevantDomains[$domain] ) ) {
-				$gtidsCommon[] = $gtid;
-			}
-		}
-
-		return $gtidsCommon;
 	}
 
 	/**
 	 * @see https://mariadb.com/kb/en/mariadb/gtid
 	 * @see https://dev.mysql.com/doc/refman/5.6/en/replication-gtids-concepts.html
-	 * @return array Map of (domain => integer position); possibly empty
+	 * @return array Map of (server_uuid/gtid_domain_id => integer position); possibly empty
 	 */
-	protected function getGtidCoordinates() {
+	protected function getActiveGtidCoordinates() {
 		$gtidInfos = [];
-		foreach ( $this->gtids as $gtid ) {
+
-			list( $domain, $pos ) = self::parseGTID( $gtid );
+		foreach ( $this->gtids as $domain => $gtid ) {
-			$gtidInfos[$domain] = $pos;
+			list( $domain, $pos, $server ) = self::parseGTID( $gtid );
+
+			$ignore = false;
+			// Filter out GTIDs from non-active replication domains
+			if ( $this->style === self::GTID_MARIA && $this->activeDomain !== null ) {
+				$ignore |= ( $domain !== $this->activeDomain );
+			}
+			// Likewise for GTIDs from non-active replication origin servers
+			if ( $this->style === self::GTID_MARIA && $this->activeServerId !== null ) {
+				$ignore |= ( $server !== $this->activeServerId );
+			} elseif ( $this->style === self::GTID_MYSQL && $this->activeServerUUID !== null ) {
+				$ignore |= ( $server !== $this->activeServerUUID );
+			}
+
+			if ( !$ignore ) {
+				$gtidInfos[$domain] = $pos;
+			}
 		}
 
 		return $gtidInfos;
 	}
 
 	/**
-	 * @param string $gtid
+	 * @param string $id GTID
-	 * @return array|null [domain, integer position] or null
+	 * @return array|null [domain ID or server UUID, sequence number, server ID/UUID] or null
 	 */
-	protected static function parseGTID( $gtid ) {
+	protected static function parseGTID( $id ) {
 		$m = [];
-		if ( preg_match( '!^(\d+)-\d+-(\d+)$!', $gtid, $m ) ) {
+		if ( preg_match( '!^(\d+)-(\d+)-(\d+)$!', $id, $m ) ) {
 			// MariaDB style: <domain>-<server id>-<sequence number>
-			return [ (int)$m[1], (int)$m[2] ];
+			return [ (int)$m[1], (int)$m[3], (int)$m[2] ];
-		} elseif ( preg_match( '!^(\w{8}-\w{4}-\w{4}-\w{4}-\w{12}):(\d+)$!', $gtid, $m ) ) {
+		} elseif ( preg_match( '!^(\w{8}-\w{4}-\w{4}-\w{4}-\w{12}):(?:\d+-|)(\d+)$!', $id, $m ) ) {
-			// MySQL style: <UUID domain>:<sequence number>
+			// MySQL style: <server UUID>:<sequence number>-<sequence number>
-			return [ $m[1], (int)$m[2] ];
+			// Normally, the first number should reflect the point (gtid_purged) where older
+			// binary logs where purged to save space. When doing comparisons, it may as well
+			// be 1 in that case. Assume that this is generally the situation.
+			return [ $m[1], (int)$m[2], $m[1] ];
 		}
 
 		return null;
@@ -194,11 +279,11 @@ class MySQLMasterPos implements DBMasterPos {
 	/**
 	 * @see https://dev.mysql.com/doc/refman/5.7/en/show-master-status.html
 	 * @see https://dev.mysql.com/doc/refman/5.7/en/show-slave-status.html
-	 * @return array|bool (binlog, (integer file number, integer position)) or false
+	 * @return array|bool Map of (binlog:<string>, pos:(<integer>, <integer>)) or false
 	 */
 	protected function getBinlogCoordinates() {
-		return ( $this->binlog !== null && $this->pos !== null )
+		return ( $this->binLog !== null && $this->logPos !== null )
-			? [ 'binlog' => $this->binlog, 'pos' => $this->pos ]
+			? [ 'binlog' => $this->binLog, 'pos' => $this->logPos ]
 			: false;
 	}
 
@@ -214,4 +299,13 @@ class MySQLMasterPos implements DBMasterPos {
 
 		$this->init( $data['position'], $data['asOfTime'] );
 	}
+
+	/**
+	 * @return string GTID set or <binary log file>/<position> (e.g db1034-bin.000976/843431247)
+	 */
+	public function __toString() {
+		return $this->gtids
+			? implode( ',', $this->gtids )
+			: $this->getLogFile() . "/{$this->logPos[self::CORD_EVENT]}";
+	}
 }

tests/phpunit/includes/libs/rdbms/database/DatabaseMysqlBaseTest.php

@@ -137,12 +137,15 @@ class DatabaseMysqlBaseTest extends PHPUnit\Framework\TestCase {
 			$db->listViews( '' ) );
 	}
 
+	/**
+	 * @covers Wikimedia\Rdbms\MySQLMasterPos
+	 */
 	public function testBinLogName() {
 		$pos = new MySQLMasterPos( "db1052.2424/4643", 1 );
 
-		$this->assertEquals( "db1052", $pos->binlog );
+		$this->assertEquals( "db1052", $pos->getLogName() );
 		$this->assertEquals( "db1052.2424", $pos->getLogFile() );
-		$this->assertEquals( [ 2424, 4643 ], $pos->pos );
+		$this->assertEquals( [ 2424, 4643 ], $pos->getLogPosition() );
 	}
 
 	/**
@@ -197,20 +200,20 @@ class DatabaseMysqlBaseTest extends PHPUnit\Framework\TestCase {
 			],
 			// MySQL GTID style
 			[
-				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:23', $now ),
+				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:1-23', $now ),
-				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:24', $now ),
+				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:5-24', $now ),
 				true,
 				false
 			],
 			[
-				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:99', $now ),
+				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:5-99', $now ),
-				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:100', $now ),
+				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:1-100', $now ),
 				true,
 				false
 			],
 			[
-				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:99', $now ),
+				new MySQLMasterPos( '3E11FA47-71CA-11E1-9E33-C80AA9429562:1-99', $now ),
-				new MySQLMasterPos( '1E11FA47-71CA-11E1-9E33-C80AA9429562:100', $now ),
+				new MySQLMasterPos( '1E11FA47-71CA-11E1-9E33-C80AA9429562:1-100', $now ),
 				false,
 				false
 			],
@@ -328,17 +331,17 @@ class DatabaseMysqlBaseTest extends PHPUnit\Framework\TestCase {
 			],
 			[
 				new MySQLMasterPos(
-					'2E11FA47-71CA-11E1-9E33-C80AA9429562:5,' .
+					'2E11FA47-71CA-11E1-9E33-C80AA9429562:1-5,' .
-					'3E11FA47-71CA-11E1-9E33-C80AA9429562:99,' .
+					'3E11FA47-71CA-11E1-9E33-C80AA9429562:20-99,' .
-					'7E11FA47-71CA-11E1-9E33-C80AA9429562:30',
+					'7E11FA47-71CA-11E1-9E33-C80AA9429562:1-30',
 					1
 				),
 				new MySQLMasterPos(
-					'1E11FA47-71CA-11E1-9E33-C80AA9429562:100,' .
+					'1E11FA47-71CA-11E1-9E33-C80AA9429562:30-100,' .
-					'3E11FA47-71CA-11E1-9E33-C80AA9429562:66',
+					'3E11FA47-71CA-11E1-9E33-C80AA9429562:30-66',
 					1
 				),
-				[ '3E11FA47-71CA-11E1-9E33-C80AA9429562:99' ]
+				[ '3E11FA47-71CA-11E1-9E33-C80AA9429562:20-99' ]
 			]
 		];
 	}
@@ -397,6 +400,155 @@ class DatabaseMysqlBaseTest extends PHPUnit\Framework\TestCase {
 		];
 	}
 
+	/**
+	 * @dataProvider provideGtidData
+	 * @covers Wikimedia\Rdbms\MySQLMasterPos
+	 * @covers Wikimedia\Rdbms\DatabaseMysqlBase::getReplicaPos
+	 * @covers Wikimedia\Rdbms\DatabaseMysqlBase::getMasterPos
+	 */
+	public function testServerGtidTable( $gtable, $rBLtable, $mBLtable, $rGTIDs, $mGTIDs ) {
+		$db = $this->getMockBuilder( DatabaseMysqli::class )
+			->disableOriginalConstructor()
+			->setMethods( [
+				'useGTIDs',
+				'getServerGTIDs',
+				'getServerRoleStatus',
+				'getServerId',
+				'getServerUUID'
+			] )
+			->getMock();
+
+		$db->method( 'useGTIDs' )->willReturn( true );
+		$db->method( 'getServerGTIDs' )->willReturn( $gtable );
+		$db->method( 'getServerRoleStatus' )->willReturnCallback(
+			function ( $role ) use ( $rBLtable, $mBLtable ) {
+				if ( $role === 'SLAVE' ) {
+					return $rBLtable;
+				} elseif ( $role === 'MASTER' ) {
+					return $mBLtable;
+				}
+
+				return null;
+			}
+		);
+		$db->method( 'getServerId' )->willReturn( 1 );
+		$db->method( 'getServerUUID' )->willReturn( '2E11FA47-71CA-11E1-9E33-C80AA9429562' );
+
+		if ( is_array( $rGTIDs ) ) {
+			$this->assertEquals( $rGTIDs, $db->getReplicaPos()->getGTIDs() );
+		} else {
+			$this->assertEquals( false, $db->getReplicaPos() );
+		}
+		if ( is_array( $mGTIDs ) ) {
+			$this->assertEquals( $mGTIDs, $db->getMasterPos()->getGTIDs() );
+		} else {
+			$this->assertEquals( false, $db->getMasterPos() );
+		}
+	}
+
+	public static function provideGtidData() {
+		return [
+			// MariaDB
+			[
+				[
+					'gtid_domain_id' => 100,
+					'gtid_current_pos' => '100-13-77',
+					'gtid_binlog_pos' => '100-13-77',
+					'gtid_slave_pos' => null // master
+				],
+				[],
+				[
+					'File' => 'host.1600',
+					'Pos' => '77'
+				],
+				[ '100' => '100-13-77' ],
+				[ '100' => '100-13-77' ]
+			],
+			[
+				[
+					'gtid_domain_id' => 100,
+					'gtid_current_pos' => '100-13-77',
+					'gtid_binlog_pos' => '100-13-77',
+					'gtid_slave_pos' => '100-13-77' // replica
+				],
+				[
+					'Relay_Master_Log_File' => 'host.1600',
+					'Exec_Master_Log_Pos' => '77'
+				],
+				[],
+				[ '100' => '100-13-77' ],
+				[ '100' => '100-13-77' ]
+			],
+			[
+				[
+					'gtid_current_pos' => '100-13-77',
+					'gtid_binlog_pos' => '100-13-77',
+					'gtid_slave_pos' => '100-13-77' // replica
+				],
+				[
+					'Relay_Master_Log_File' => 'host.1600',
+					'Exec_Master_Log_Pos' => '77'
+				],
+				[],
+				[ '100' => '100-13-77' ],
+				[ '100' => '100-13-77' ]
+			],
+			// MySQL
+			[
+				[
+					'gtid_executed' => '2E11FA47-71CA-11E1-9E33-C80AA9429562:1-77'
+				],
+				[
+					'Relay_Master_Log_File' => 'host.1600',
+					'Exec_Master_Log_Pos' => '77'
+				],
+				[], // only a replica
+				[ '2E11FA47-71CA-11E1-9E33-C80AA9429562'
+					=> '2E11FA47-71CA-11E1-9E33-C80AA9429562:1-77' ],
+				// replica/master use same var
+				[ '2E11FA47-71CA-11E1-9E33-C80AA9429562'
+					=> '2E11FA47-71CA-11E1-9E33-C80AA9429562:1-77' ],
+			],
+			[
+				[
+					'gtid_executed' => '2E11FA47-71CA-11E1-9E33-C80AA9429562:1-49,' .
+						'2E11FA47-71CA-11E1-9E33-C80AA9429562:51-77'
+				],
+				[
+					'Relay_Master_Log_File' => 'host.1600',
+					'Exec_Master_Log_Pos' => '77'
+				],
+				[], // only a replica
+				[ '2E11FA47-71CA-11E1-9E33-C80AA9429562'
+					=> '2E11FA47-71CA-11E1-9E33-C80AA9429562:51-77' ],
+				// replica/master use same var
+				[ '2E11FA47-71CA-11E1-9E33-C80AA9429562'
+					=> '2E11FA47-71CA-11E1-9E33-C80AA9429562:51-77' ],
+			],
+			[
+				[
+					'gtid_executed' => null // not enabled?
+				],
+				[
+					'Relay_Master_Log_File' => 'host.1600',
+					'Exec_Master_Log_Pos' => '77'
+				],
+				[], // only a replica
+				[], // binlog fallback
+				false
+			],
+			[
+				[
+					'gtid_executed' => null // not enabled?
+				],
+				[], // no replication
+				[], // no replication
+				false,
+				false
+			]
+		];
+	}
+
 	/**
 	 * @covers Wikimedia\Rdbms\MySQLMasterPos
 	 */