NameTableStore.php

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<?php
namespace MediaWiki\Storage;
 
use IExpiringStore;
use Psr\Log\LoggerInterface;
use WANObjectCache;
use Wikimedia\Assert\Assert;
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\ILoadBalancer;
 
class NameTableStore {
 
    private $loadBalancer;
 
    private $cache;
 
    private $logger;
 
    private $tableCache = null;
 
    private $wikiId = false;
 
    private $cacheTTL;
 
    private $table;
    private $idField;
    private $nameField;
    private $normalizationCallback = null;
    private $insertCallback = null;
 
    public function __construct(
        ILoadBalancer $dbLoadBalancer,
        WANObjectCache $cache,
        LoggerInterface $logger,
        $table,
        $idField,
        $nameField,
        callable $normalizationCallback = null,
        $wikiId = false,
        callable $insertCallback = null
    ) {
        $this->loadBalancer = $dbLoadBalancer;
        $this->cache = $cache;
        $this->logger = $logger;
        $this->table = $table;
        $this->idField = $idField;
        $this->nameField = $nameField;
        $this->normalizationCallback = $normalizationCallback;
        $this->wikiId = $wikiId;
        $this->cacheTTL = IExpiringStore::TTL_MONTH;
        $this->insertCallback = $insertCallback;
    }
 
    private function getDBConnection( $index, $flags = 0 ) {
        return $this->loadBalancer->getConnection( $index, [], $this->wikiId, $flags );
    }
 
    private function getCacheKey() {
        return $this->cache->makeGlobalKey(
            'NameTableSqlStore',
            $this->table,
            $this->loadBalancer->resolveDomainID( $this->wikiId )
        );
    }
 
    private function normalizeName( $name ) {
        if ( $this->normalizationCallback === null ) {
            return $name;
        }
        return call_user_func( $this->normalizationCallback, $name );
    }
 
    public function acquireId( $name ) {
        Assert::parameterType( 'string', $name, '$name' );
        $name = $this->normalizeName( $name );
 
        $table = $this->getTableFromCachesOrReplica();
        $searchResult = array_search( $name, $table, true );
        if ( $searchResult === false ) {
            $id = $this->store( $name );
            if ( $id === null ) {
                // RACE: $name was already in the db, probably just inserted, so load from master.
                // Use DBO_TRX to avoid missing inserts due to other threads or REPEATABLE-READs.
                // ...but not during unit tests, because we need the fake DB tables of the default
                // connection.
                $connFlags = defined( 'MW_PHPUNIT_TEST' ) ? 0 : ILoadBalancer::CONN_TRX_AUTOCOMMIT;
                $table = $this->reloadMap( $connFlags );
 
                $searchResult = array_search( $name, $table, true );
                if ( $searchResult === false ) {
                    // Insert failed due to IGNORE flag, but DB_MASTER didn't give us the data
                    $m = "No insert possible but master didn't give us a record for " .
                        "'{$name}' in '{$this->table}'";
                    $this->logger->error( $m );
                    throw new NameTableAccessException( $m );
                }
            } elseif ( isset( $table[$id] ) ) {
                throw new NameTableAccessException(
                    "Expected unused ID from database insert for '$name' "
                    . " into '{$this->table}', but ID $id is already associated with"
                    . " the name '{$table[$id]}'! This may indicate database corruption!" );
            } else {
                $table[$id] = $name;
                $searchResult = $id;
 
                // As store returned an ID we know we inserted so delete from WAN cache
                $this->purgeWANCache(
                    function () {
                        $this->cache->delete( $this->getCacheKey() );
                    }
                );
            }
            $this->tableCache = $table;
        }
 
        return $searchResult;
    }
 
    public function reloadMap( $connFlags = 0 ) {
        $this->tableCache = $this->loadTable(
            $this->getDBConnection( DB_MASTER, $connFlags )
        );
        $this->purgeWANCache(
            function () {
                $this->cache->reap( $this->getCacheKey(), INF );
            }
        );
 
        return $this->tableCache;
    }
 
    public function getId( $name ) {
        Assert::parameterType( 'string', $name, '$name' );
        $name = $this->normalizeName( $name );
 
        $table = $this->getTableFromCachesOrReplica();
        $searchResult = array_search( $name, $table, true );
 
        if ( $searchResult !== false ) {
            return $searchResult;
        }
 
        throw NameTableAccessException::newFromDetails( $this->table, 'name', $name );
    }
 
    public function getName( $id ) {
        Assert::parameterType( 'integer', $id, '$id' );
 
        $table = $this->getTableFromCachesOrReplica();
        if ( array_key_exists( $id, $table ) ) {
            return $table[$id];
        }
        $fname = __METHOD__;
 
        $table = $this->cache->getWithSetCallback(
            $this->getCacheKey(),
            $this->cacheTTL,
            function ( $oldValue, &$ttl, &$setOpts ) use ( $id, $fname ) {
                // Check if cached value is up-to-date enough to have $id
                if ( is_array( $oldValue ) && array_key_exists( $id, $oldValue ) ) {
                    // Completely leave the cache key alone
                    $ttl = WANObjectCache::TTL_UNCACHEABLE;
                    // Use the old value
                    return $oldValue;
                }
                // Regenerate from replica DB, and master DB if needed
                foreach ( [ DB_REPLICA, DB_MASTER ] as $source ) {
                    // Log a fallback to master
                    if ( $source === DB_MASTER ) {
                        $this->logger->info(
                            $fname . ' falling back to master select from ' .
                            $this->table . ' with id ' . $id
                        );
                    }
                    $db = $this->getDBConnection( $source );
                    $cacheSetOpts = Database::getCacheSetOptions( $db );
                    $table = $this->loadTable( $db );
                    if ( array_key_exists( $id, $table ) ) {
                        break; // found it
                    }
                }
                // Use the value from last source checked
                $setOpts += $cacheSetOpts;
 
                return $table;
            },
            [ 'minAsOf' => INF ] // force callback run
        );
 
        $this->tableCache = $table;
 
        if ( array_key_exists( $id, $table ) ) {
            return $table[$id];
        }
 
        throw NameTableAccessException::newFromDetails( $this->table, 'id', $id );
    }
 
    public function getMap() {
        return $this->getTableFromCachesOrReplica();
    }
 
    private function getTableFromCachesOrReplica() {
        if ( $this->tableCache !== null ) {
            return $this->tableCache;
        }
 
        $table = $this->cache->getWithSetCallback(
            $this->getCacheKey(),
            $this->cacheTTL,
            function ( $oldValue, &$ttl, &$setOpts ) {
                $dbr = $this->getDBConnection( DB_REPLICA );
                $setOpts += Database::getCacheSetOptions( $dbr );
                return $this->loadTable( $dbr );
            }
        );
 
        $this->tableCache = $table;
 
        return $table;
    }
 
    private function purgeWANCache( $purgeCallback ) {
        // If the LB has no DB changes don't both with onTransactionPreCommitOrIdle
        if ( !$this->loadBalancer->hasOrMadeRecentMasterChanges() ) {
            $purgeCallback();
            return;
        }
 
        $this->getDBConnection( DB_MASTER )
            ->onTransactionPreCommitOrIdle( $purgeCallback, __METHOD__ );
    }
 
    private function loadTable( IDatabase $db ) {
        $result = $db->select(
            $this->table,
            [
                'id' => $this->idField,
                'name' => $this->nameField
            ],
            [],
            __METHOD__,
            [ 'ORDER BY' => 'id' ]
        );
 
        $assocArray = [];
        foreach ( $result as $row ) {
            $assocArray[$row->id] = $row->name;
        }
 
        return $assocArray;
    }
 
    private function store( $name ) {
        Assert::parameterType( 'string', $name, '$name' );
        Assert::parameter( $name !== '', '$name', 'should not be an empty string' );
        // Note: this is only called internally so normalization of $name has already occurred.
 
        $dbw = $this->getDBConnection( DB_MASTER );
 
        $dbw->insert(
            $this->table,
            $this->getFieldsToStore( $name ),
            __METHOD__,
            [ 'IGNORE' ]
        );
 
        if ( $dbw->affectedRows() === 0 ) {
            $this->logger->info(
                'Tried to insert name into table ' . $this->table . ', but value already existed.'
            );
            return null;
        }
 
        return $dbw->insertId();
    }
 
    private function getFieldsToStore( $name ) {
        $fields = [ $this->nameField => $name ];
        if ( $this->insertCallback !== null ) {
            $fields = call_user_func( $this->insertCallback, $fields );
        }
        return $fields;
    }
 
}