Allow DB config to be reloaded on the fly

This introduces $wgLBFactoryConf['configCallback'] which can be set to a
function that returns updates to be applied to $wgLBFactoryConf. The new
method LBFactory::autoreConfigure() can be called to check the callabck
and, if the config changed, reconfigure all existing LoadBalancers.

Reconfiguring the LoadBalancers causes all open connections to be
invalidated; however, any DBConnRef instances will remain valid and will
acquire a fresh connection from the LoadBalancer automatically when
appropriate.

As a proof of concept, this patch adds support for config reloding
into WikiExporter.

Bug: T298485
Change-Id: I6c3ffde62f6e038730736abe980befd90ec43e1a

1 files changed, 82 insertions, 43 deletions

diff --git a/includes/db/MWLBFactory.php b/includes/db/MWLBFactory.php
index 7fbcd2873b06..81cea3d78e7b 100644
--- a/includes/db/MWLBFactory.php
+++ b/includes/db/MWLBFactory.php
@@ -38,7 +38,7 @@ use Wikimedia\RequestTimeout\CriticalSectionProvider;
  * @internal For use by core ServiceWiring only.
  * @ingroup Database
  */
-abstract class MWLBFactory {
+class MWLBFactory {
 
 	/** @var array Cache of already-logged deprecation messages */
 	private static $loggedDeprecations = [];
@@ -67,9 +67,36 @@ abstract class MWLBFactory {
 		MainConfigNames::SQLiteDataDir,
 		MainConfigNames::SQLMode,
 	];
+	/**
+	 * @var ServiceOptions
+	 */
+	private $options;
+	/**
+	 * @var ConfiguredReadOnlyMode
+	 */
+	private $readOnlyMode;
+	/**
+	 * @var BagOStuff
+	 */
+	private $cpStash;
+	/**
+	 * @var BagOStuff
+	 */
+	private $srvCache;
+	/**
+	 * @var WANObjectCache
+	 */
+	private $wanCache;
+	/**
+	 * @var CriticalSectionProvider
+	 */
+	private $csProvider;
+	/**
+	 * @var StatsdDataFactoryInterface
+	 */
+	private $statsdDataFactory;
 
 	/**
-	 * @param array $lbConf Config for LBFactory::__construct()
 	 * @param ServiceOptions $options
 	 * @param ConfiguredReadOnlyMode $readOnlyMode
 	 * @param BagOStuff $cpStash
@@ -77,11 +104,8 @@ abstract class MWLBFactory {
 	 * @param WANObjectCache $wanCache
 	 * @param CriticalSectionProvider $csProvider
 	 * @param StatsdDataFactoryInterface $statsdDataFactory
-	 * @return array
-	 * @internal For use with service wiring
 	 */
-	public static function applyDefaultConfig(
-		array $lbConf,
+	public function __construct(
 		ServiceOptions $options,
 		ConfiguredReadOnlyMode $readOnlyMode,
 		BagOStuff $cpStash,
@@ -90,15 +114,30 @@ abstract class MWLBFactory {
 		CriticalSectionProvider $csProvider,
 		StatsdDataFactoryInterface $statsdDataFactory
 	) {
-		$options->assertRequiredOptions( self::APPLY_DEFAULT_CONFIG_OPTIONS );
+		$this->options = $options;
+		$this->readOnlyMode = $readOnlyMode;
+		$this->cpStash = $cpStash;
+		$this->srvCache = $srvCache;
+		$this->wanCache = $wanCache;
+		$this->csProvider = $csProvider;
+		$this->statsdDataFactory = $statsdDataFactory;
+	}
+
+	/**
+	 * @param array $lbConf Config for LBFactory::__construct()
+	 * @return array
+	 * @internal For use with service wiring
+	 */
+	public function applyDefaultConfig( array $lbConf ) {
+		$this->options->assertRequiredOptions( self::APPLY_DEFAULT_CONFIG_OPTIONS );
 
 		$typesWithSchema = self::getDbTypesWithSchemas();
 
 		$lbConf += [
 			'localDomain' => new DatabaseDomain(
-				$options->get( MainConfigNames::DBname ),
-				$options->get( MainConfigNames::DBmwschema ),
-				$options->get( MainConfigNames::DBprefix )
+				$this->options->get( MainConfigNames::DBname ),
+				$this->options->get( MainConfigNames::DBmwschema ),
+				$this->options->get( MainConfigNames::DBprefix )
 			),
 			'profiler' => static function ( $section ) {
 				return Profiler::instance()->scopedProfileIn( $section );
@@ -110,11 +149,11 @@ abstract class MWLBFactory {
 			'perfLogger' => LoggerFactory::getInstance( 'DBPerformance' ),
 			'errorLogger' => [ MWExceptionHandler::class, 'logException' ],
 			'deprecationLogger' => [ static::class, 'logDeprecation' ],
-			'statsdDataFactory' => $statsdDataFactory,
-			'cliMode' => $options->get( 'CommandLineMode' ),
-			'readOnlyReason' => $readOnlyMode->getReason(),
-			'defaultGroup' => $options->get( MainConfigNames::DBDefaultGroup ),
-			'criticalSectionProvider' => $csProvider
+			'statsdDataFactory' => $this->statsdDataFactory,
+			'cliMode' => $this->options->get( 'CommandLineMode' ),
+			'readOnlyReason' => $this->readOnlyMode->getReason(),
+			'defaultGroup' => $this->options->get( MainConfigNames::DBDefaultGroup ),
+			'criticalSectionProvider' => $this->csProvider
 		];
 
 		$serversCheck = [];
@@ -124,55 +163,55 @@ abstract class MWLBFactory {
 		if ( $lbConf['class'] === Wikimedia\Rdbms\LBFactorySimple::class ) {
 			if ( isset( $lbConf['servers'] ) ) {
 				// Server array is already explicitly configured
-			} elseif ( is_array( $options->get( MainConfigNames::DBservers ) ) ) {
+			} elseif ( is_array( $this->options->get( MainConfigNames::DBservers ) ) ) {
 				$lbConf['servers'] = [];
-				foreach ( $options->get( MainConfigNames::DBservers ) as $i => $server ) {
-					$lbConf['servers'][$i] = self::initServerInfo( $server, $options );
+				foreach ( $this->options->get( MainConfigNames::DBservers ) as $i => $server ) {
+					$lbConf['servers'][$i] = self::initServerInfo( $server, $this->options );
 				}
 			} else {
 				$server = self::initServerInfo(
 					[
-						'host' => $options->get( MainConfigNames::DBserver ),
-						'user' => $options->get( MainConfigNames::DBuser ),
-						'password' => $options->get( MainConfigNames::DBpassword ),
-						'dbname' => $options->get( MainConfigNames::DBname ),
-						'type' => $options->get( MainConfigNames::DBtype ),
+						'host' => $this->options->get( MainConfigNames::DBserver ),
+						'user' => $this->options->get( MainConfigNames::DBuser ),
+						'password' => $this->options->get( MainConfigNames::DBpassword ),
+						'dbname' => $this->options->get( MainConfigNames::DBname ),
+						'type' => $this->options->get( MainConfigNames::DBtype ),
 						'load' => 1
 					],
-					$options
+					$this->options
 				);
 
-				if ( $options->get( MainConfigNames::DBssl ) ) {
+				if ( $this->options->get( MainConfigNames::DBssl ) ) {
 					$server['ssl'] = true;
 				}
-				$server['flags'] |= $options->get( MainConfigNames::DBcompress ) ? DBO_COMPRESS : 0;
+				$server['flags'] |= $this->options->get( MainConfigNames::DBcompress ) ? DBO_COMPRESS : 0;
 
 				$lbConf['servers'] = [ $server ];
 			}
 			if ( !isset( $lbConf['externalClusters'] ) ) {
-				$lbConf['externalClusters'] = $options->get( MainConfigNames::ExternalServers );
+				$lbConf['externalClusters'] = $this->options->get( MainConfigNames::ExternalServers );
 			}
 
 			$serversCheck = $lbConf['servers'];
 		} elseif ( $lbConf['class'] === Wikimedia\Rdbms\LBFactoryMulti::class ) {
 			if ( isset( $lbConf['serverTemplate'] ) ) {
 				if ( in_array( $lbConf['serverTemplate']['type'], $typesWithSchema, true ) ) {
-					$lbConf['serverTemplate']['schema'] = $options->get( MainConfigNames::DBmwschema );
+					$lbConf['serverTemplate']['schema'] = $this->options->get( MainConfigNames::DBmwschema );
 				}
-				$lbConf['serverTemplate']['sqlMode'] = $options->get( MainConfigNames::SQLMode );
+				$lbConf['serverTemplate']['sqlMode'] = $this->options->get( MainConfigNames::SQLMode );
 				$serversCheck = [ $lbConf['serverTemplate'] ];
 			}
 		}
 
 		self::assertValidServerConfigs(
 			$serversCheck,
-			$options->get( MainConfigNames::DBname ),
-			$options->get( MainConfigNames::DBprefix )
+			$this->options->get( MainConfigNames::DBname ),
+			$this->options->get( MainConfigNames::DBprefix )
 		);
 
-		$lbConf['cpStash'] = $cpStash;
-		$lbConf['srvCache'] = $srvCache;
-		$lbConf['wanCache'] = $wanCache;
+		$lbConf['cpStash'] = $this->cpStash;
+		$lbConf['srvCache'] = $this->srvCache;
+		$lbConf['wanCache'] = $this->wanCache;
 
 		return $lbConf;
 	}
@@ -180,7 +219,7 @@ abstract class MWLBFactory {
 	/**
 	 * @return array
 	 */
-	private static function getDbTypesWithSchemas() {
+	private function getDbTypesWithSchemas() {
 		return [ 'postgres' ];
 	}
 
@@ -189,7 +228,7 @@ abstract class MWLBFactory {
 	 * @param ServiceOptions $options
 	 * @return array
 	 */
-	private static function initServerInfo( array $server, ServiceOptions $options ) {
+	private function initServerInfo( array $server, ServiceOptions $options ) {
 		if ( $server['type'] === 'sqlite' ) {
 			$httpMethod = $_SERVER['REQUEST_METHOD'] ?? null;
 			// T93097: hint for how file-based databases (e.g. sqlite) should go about locking.
@@ -238,7 +277,7 @@ abstract class MWLBFactory {
 	 * @param string $ldDB Local domain database name
 	 * @param string $ldTP Local domain prefix
 	 */
-	private static function assertValidServerConfigs( array $servers, $ldDB, $ldTP ) {
+	private function assertValidServerConfigs( array $servers, $ldDB, $ldTP ) {
 		foreach ( $servers as $server ) {
 			$type = $server['type'] ?? null;
 			$srvDB = $server['dbname'] ?? null; // server DB
@@ -267,7 +306,7 @@ abstract class MWLBFactory {
 	 * @param string $dbType Database type
 	 * @return never
 	 */
-	private static function reportIfPrefixSet( $prefix, $dbType ) {
+	private function reportIfPrefixSet( $prefix, $dbType ) {
 		$e = new UnexpectedValueException(
 			"\$wgDBprefix is set to '$prefix' but the database type is '$dbType'. " .
 			"MediaWiki does not support using a table prefix with this RDBMS type."
@@ -281,7 +320,7 @@ abstract class MWLBFactory {
 	 * @param string $ldDB Local DB domain database
 	 * @return never
 	 */
-	private static function reportMismatchedDBs( $srvDB, $ldDB ) {
+	private function reportMismatchedDBs( $srvDB, $ldDB ) {
 		$e = new UnexpectedValueException(
 			"\$wgDBservers has dbname='$srvDB' but \$wgDBname='$ldDB'. " .
 			"Set \$wgDBname to the database used by this wiki project. " .
@@ -299,7 +338,7 @@ abstract class MWLBFactory {
 	 * @param string $ldTP Local DB domain database
 	 * @return never
 	 */
-	private static function reportMismatchedPrefixes( $srvTP, $ldTP ) {
+	private function reportMismatchedPrefixes( $srvTP, $ldTP ) {
 		$e = new UnexpectedValueException(
 			"\$wgDBservers has tablePrefix='$srvTP' but \$wgDBprefix='$ldTP'. " .
 			"Set \$wgDBprefix to the table prefix used by this wiki project. " .
@@ -319,7 +358,7 @@ abstract class MWLBFactory {
 	 * @param array $config (e.g. $wgLBFactoryConf)
 	 * @return string Class name
 	 */
-	public static function getLBFactoryClass( array $config ) {
+	public function getLBFactoryClass( array $config ) {
 		$compat = [
 			// For LocalSettings.php compat after removing underscores (since 1.23).
 			'LBFactory_Single' => Wikimedia\Rdbms\LBFactorySingle::class,
@@ -338,7 +377,7 @@ abstract class MWLBFactory {
 	/**
 	 * @param ILBFactory $lbFactory
 	 */
-	public static function setDomainAliases( ILBFactory $lbFactory ) {
+	public function setDomainAliases( ILBFactory $lbFactory ) {
 		$domain = DatabaseDomain::newFromId( $lbFactory->getLocalDomainID() );
 		// For compatibility with hyphenated $wgDBname values on older wikis, handle callers
 		// that assume corresponding database domain IDs and wiki IDs have identical values
@@ -372,7 +411,7 @@ abstract class MWLBFactory {
 	 * @param Config $config
 	 * @param IBufferingStatsdDataFactory $stats
 	 */
-	public static function applyGlobalState(
+	public function applyGlobalState(
 		ILBFactory $lbFactory,
 		Config $config,
 		IBufferingStatsdDataFactory $stats