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[mediawiki.git] / includes / clientpool / RedisConnectionPool.php

<?php
/**
 * Redis client connection pooling 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
 * @defgroup Redis Redis
 * @author Aaron Schulz
 */

/**
 * Helper class to manage Redis connections.
 *
 * This can be used to get handle wrappers that free the handle when the wrapper
 * leaves scope. The maximum number of free handles (connections) is configurable.
 * This provides an easy way to cache connection handles that may also have state,
 * such as a handle does between multi() and exec(), and without hoarding connections.
 * The wrappers use PHP magic methods so that calling functions on them calls the
 * function of the actual Redis object handle.
 *
 * @ingroup Redis
 * @since 1.21
 */
class RedisConnectionPool {
        /**
         * @name Pool settings.
         * Settings there are shared for any connection made in this pool.
         * See the singleton() method documentation for more details.
         * @{
         */
        /** @var string Connection timeout in seconds */
        protected $connectTimeout;
        /** @var string Read timeout in seconds */
        protected $readTimeout;
        /** @var string Plaintext auth password */
        protected $password;
        /** @var bool Whether connections persist */
        protected $persistent;
        /** @var int Serializer to use (Redis::SERIALIZER_*) */
        protected $serializer;
        /** @} */

        /** @var int Current idle pool size */
        protected $idlePoolSize = 0;

        /** @var array (server name => ((connection info array),...) */
        protected $connections = array();
        /** @var array (server name => UNIX timestamp) */
        protected $downServers = array();

        /** @var array (pool ID => RedisConnectionPool) */
        protected static $instances = array();

        /** integer; seconds to cache servers as "down". */
        const SERVER_DOWN_TTL = 30;

        /**
         * @param array $options
         * @throws MWException
         */
        protected function __construct( array $options ) {
                if ( !class_exists( 'Redis' ) ) {
                        throw new MWException( __CLASS__ . ' requires a Redis client library. ' .
                                'See https://www.mediawiki.org/wiki/Redis#Setup' );
                }
                $this->connectTimeout = $options['connectTimeout'];
                $this->readTimeout = $options['readTimeout'];
                $this->persistent = $options['persistent'];
                $this->password = $options['password'];
                if ( !isset( $options['serializer'] ) || $options['serializer'] === 'php' ) {
                        $this->serializer = Redis::SERIALIZER_PHP;
                } elseif ( $options['serializer'] === 'igbinary' ) {
                        $this->serializer = Redis::SERIALIZER_IGBINARY;
                } elseif ( $options['serializer'] === 'none' ) {
                        $this->serializer = Redis::SERIALIZER_NONE;
                } else {
                        throw new MWException( "Invalid serializer specified." );
                }
        }

        /**
         * @param array $options
         * @return array
         */
        protected static function applyDefaultConfig( array $options ) {
                if ( !isset( $options['connectTimeout'] ) ) {
                        $options['connectTimeout'] = 1;
                }
                if ( !isset( $options['readTimeout'] ) ) {
                        $options['readTimeout'] = 1;
                }
                if ( !isset( $options['persistent'] ) ) {
                        $options['persistent'] = false;
                }
                if ( !isset( $options['password'] ) ) {
                        $options['password'] = null;
                }

                return $options;
        }

        /**
         * @param array $options
         * $options include:
         *   - connectTimeout : The timeout for new connections, in seconds.
         *                      Optional, default is 1 second.
         *   - readTimeout    : The timeout for operation reads, in seconds.
         *                      Commands like BLPOP can fail if told to wait longer than this.
         *                      Optional, default is 1 second.
         *   - persistent     : Set this to true to allow connections to persist across
         *                      multiple web requests. False by default.
         *   - password       : The authentication password, will be sent to Redis in clear text.
         *                      Optional, if it is unspecified, no AUTH command will be sent.
         *   - serializer     : Set to "php", "igbinary", or "none". Default is "php".
         * @return RedisConnectionPool
         */
        public static function singleton( array $options ) {
                $options = self::applyDefaultConfig( $options );
                // Map the options to a unique hash...
                ksort( $options ); // normalize to avoid pool fragmentation
                $id = sha1( serialize( $options ) );
                // Initialize the object at the hash as needed...
                if ( !isset( self::$instances[$id] ) ) {
                        self::$instances[$id] = new self( $options );
                        wfDebug( "Creating a new " . __CLASS__ . " instance with id $id.\n" );
                }

                return self::$instances[$id];
        }

        /**
         * Get a connection to a redis server. Based on code in RedisBagOStuff.php.
         *
         * @param string $server A hostname/port combination or the absolute path of a UNIX socket.
         *                       If a hostname is specified but no port, port 6379 will be used.
         * @return RedisConnRef|bool Returns false on failure
         * @throws MWException
         */
        public function getConnection( $server ) {
                // Check the listing "dead" servers which have had a connection errors.
                // Servers are marked dead for a limited period of time, to
                // avoid excessive overhead from repeated connection timeouts.
                if ( isset( $this->downServers[$server] ) ) {
                        $now = time();
                        if ( $now > $this->downServers[$server] ) {
                                // Dead time expired
                                unset( $this->downServers[$server] );
                        } else {
                                // Server is dead
                                wfDebug( "server $server is marked down for another " .
                                        ( $this->downServers[$server] - $now ) . " seconds, can't get connection\n" );

                                return false;
                        }
                }

                // Check if a connection is already free for use
                if ( isset( $this->connections[$server] ) ) {
                        foreach ( $this->connections[$server] as &$connection ) {
                                if ( $connection['free'] ) {
                                        $connection['free'] = false;
                                        --$this->idlePoolSize;

                                        return new RedisConnRef( $this, $server, $connection['conn'] );
                                }
                        }
                }

                if ( substr( $server, 0, 1 ) === '/' ) {
                        // UNIX domain socket
                        // These are required by the redis extension to start with a slash, but
                        // we still need to set the port to a special value to make it work.
                        $host = $server;
                        $port = 0;
                } else {
                        // TCP connection
                        $hostPort = IP::splitHostAndPort( $server );
                        if ( !$hostPort ) {
                                throw new MWException( __CLASS__ . ": invalid configured server \"$server\"" );
                        }
                        list( $host, $port ) = $hostPort;
                        if ( $port === false ) {
                                $port = 6379;
                        }
                }

                $conn = new Redis();
                try {
                        if ( $this->persistent ) {
                                $result = $conn->pconnect( $host, $port, $this->connectTimeout );
                        } else {
                                $result = $conn->connect( $host, $port, $this->connectTimeout );
                        }
                        if ( !$result ) {
                                wfDebugLog( 'redis', "Could not connect to server $server" );
                                // Mark server down for some time to avoid further timeouts
                                $this->downServers[$server] = time() + self::SERVER_DOWN_TTL;

                                return false;
                        }
                        if ( $this->password !== null ) {
                                if ( !$conn->auth( $this->password ) ) {
                                        wfDebugLog( 'redis', "Authentication error connecting to $server" );
                                }
                        }
                } catch ( RedisException $e ) {
                        $this->downServers[$server] = time() + self::SERVER_DOWN_TTL;
                        wfDebugLog( 'redis', "Redis exception connecting to $server: " . $e->getMessage() );

                        return false;
                }

                if ( $conn ) {
                        $conn->setOption( Redis::OPT_READ_TIMEOUT, $this->readTimeout );
                        $conn->setOption( Redis::OPT_SERIALIZER, $this->serializer );
                        $this->connections[$server][] = array( 'conn' => $conn, 'free' => false );

                        return new RedisConnRef( $this, $server, $conn );
                } else {
                        return false;
                }
        }

        /**
         * Mark a connection to a server as free to return to the pool
         *
         * @param string $server
         * @param Redis $conn
         * @return bool
         */
        public function freeConnection( $server, Redis $conn ) {
                $found = false;

                foreach ( $this->connections[$server] as &$connection ) {
                        if ( $connection['conn'] === $conn && !$connection['free'] ) {
                                $connection['free'] = true;
                                ++$this->idlePoolSize;
                                break;
                        }
                }

                $this->closeExcessIdleConections();

                return $found;
        }

        /**
         * Close any extra idle connections if there are more than the limit
         */
        protected function closeExcessIdleConections() {
                if ( $this->idlePoolSize <= count( $this->connections ) ) {
                        return; // nothing to do (no more connections than servers)
                }

                foreach ( $this->connections as &$serverConnections ) {
                        foreach ( $serverConnections as $key => &$connection ) {
                                if ( $connection['free'] ) {
                                        unset( $serverConnections[$key] );
                                        if ( --$this->idlePoolSize <= count( $this->connections ) ) {
                                                return; // done (no more connections than servers)
                                        }
                                }
                        }
                }
        }

        /**
         * The redis extension throws an exception in response to various read, write
         * and protocol errors. Sometimes it also closes the connection, sometimes
         * not. The safest response for us is to explicitly destroy the connection
         * object and let it be reopened during the next request.
         *
         * @param string $server
         * @param RedisConnRef $cref
         * @param RedisException $e
         * @deprecated since 1.23
         */
        public function handleException( $server, RedisConnRef $cref, RedisException $e ) {
                return $this->handleError( $cref, $e );
        }

        /**
         * The redis extension throws an exception in response to various read, write
         * and protocol errors. Sometimes it also closes the connection, sometimes
         * not. The safest response for us is to explicitly destroy the connection
         * object and let it be reopened during the next request.
         *
         * @param RedisConnRef $cref
         * @param RedisException $e
         */
        public function handleError( RedisConnRef $cref, RedisException $e ) {
                $server = $cref->getServer();
                wfDebugLog( 'redis', "Redis exception on server $server: " . $e->getMessage() . "\n" );
                foreach ( $this->connections[$server] as $key => $connection ) {
                        if ( $cref->isConnIdentical( $connection['conn'] ) ) {
                                $this->idlePoolSize -= $connection['free'] ? 1 : 0;
                                unset( $this->connections[$server][$key] );
                                break;
                        }
                }
        }

        /**
         * Re-send an AUTH request to the redis server (useful after disconnects).
         *
         * This works around an upstream bug in phpredis. phpredis hides disconnects by transparently
         * reconnecting, but it neglects to re-authenticate the new connection. To the user of the
         * phpredis client API this manifests as a seemingly random tendency of connections to lose
         * their authentication status.
         *
         * This method is for internal use only.
         *
         * @see https://github.com/nicolasff/phpredis/issues/403
         *
         * @param string $server
         * @param Redis $conn
         * @return bool Success
         */
        public function reauthenticateConnection( $server, Redis $conn ) {
                if ( $this->password !== null ) {
                        if ( !$conn->auth( $this->password ) ) {
                                wfDebugLog( 'redis', "Authentication error connecting to $server" );

                                return false;
                        }
                }

                return true;
        }

        /**
         * Adjust or reset the connection handle read timeout value
         *
         * @param Redis $conn
         * @param int $timeout Optional
         */
        public function resetTimeout( Redis $conn, $timeout = null ) {
                $conn->setOption( Redis::OPT_READ_TIMEOUT, $timeout ?: $this->readTimeout );
        }

        /**
         * Make sure connections are closed for sanity
         */
        function __destruct() {
                foreach ( $this->connections as $server => &$serverConnections ) {
                        foreach ( $serverConnections as $key => &$connection ) {
                                $connection['conn']->close();
                        }
                }
        }
}

/**
 * Helper class to handle automatically marking connectons as reusable (via RAII pattern)
 *
 * This class simply wraps the Redis class and can be used the same way
 *
 * @ingroup Redis
 * @since 1.21
 */
class RedisConnRef {
        /** @var RedisConnectionPool */
        protected $pool;
        /** @var Redis */
        protected $conn;

        protected $server; // string
        protected $lastError; // string

        /**
         * @param RedisConnectionPool $pool
         * @param string $server
         * @param Redis $conn
         */
        public function __construct( RedisConnectionPool $pool, $server, Redis $conn ) {
                $this->pool = $pool;
                $this->server = $server;
                $this->conn = $conn;
        }

        /**
         * @return string
         * @since 1.23
         */
        public function getServer() {
                return $this->server;
        }

        public function getLastError() {
                return $this->lastError;
        }

        public function clearLastError() {
                $this->lastError = null;
        }

        public function __call( $name, $arguments ) {
                $conn = $this->conn; // convenience

                // Work around https://github.com/nicolasff/phpredis/issues/70
                $lname = strtolower( $name );
                if ( ( $lname === 'blpop' || $lname == 'brpop' )
                        && is_array( $arguments[0] ) && isset( $arguments[1] )
                ) {
                        $this->pool->resetTimeout( $conn, $arguments[1] + 1 );
                } elseif ( $lname === 'brpoplpush' && isset( $arguments[2] ) ) {
                        $this->pool->resetTimeout( $conn, $arguments[2] + 1 );
                }

                $conn->clearLastError();
                try {
                        $res = call_user_func_array( array( $conn, $name ), $arguments );
                        if ( preg_match( '/^ERR operation not permitted\b/', $conn->getLastError() ) ) {
                                $this->pool->reauthenticateConnection( $this->server, $conn );
                                $conn->clearLastError();
                                $res = call_user_func_array( array( $conn, $name ), $arguments );
                                wfDebugLog( 'redis', "Used automatic re-authentication for method '$name'." );
                        }
                } catch ( RedisException $e ) {
                        $this->pool->resetTimeout( $conn ); // restore
                        throw $e;
                }

                $this->lastError = $conn->getLastError() ?: $this->lastError;

                $this->pool->resetTimeout( $conn ); // restore

                return $res;
        }

        /**
         * @param string $script
         * @param array $params
         * @param int $numKeys
         * @return mixed
         * @throws RedisException
         */
        public function luaEval( $script, array $params, $numKeys ) {
                $sha1 = sha1( $script ); // 40 char hex
                $conn = $this->conn; // convenience
                $server = $this->server; // convenience

                // Try to run the server-side cached copy of the script
                $conn->clearLastError();
                $res = $conn->evalSha( $sha1, $params, $numKeys );
                // If we got a permission error reply that means that (a) we are not in
                // multi()/pipeline() and (b) some connection problem likely occurred. If
                // the password the client gave was just wrong, an exception should have
                // been thrown back in getConnection() previously.
                if ( preg_match( '/^ERR operation not permitted\b/', $conn->getLastError() ) ) {
                        $this->pool->reauthenticateConnection( $server, $conn );
                        $conn->clearLastError();
                        $res = $conn->eval( $script, $params, $numKeys );
                        wfDebugLog( 'redis', "Used automatic re-authentication for Lua script $sha1." );
                }
                // If the script is not in cache, use eval() to retry and cache it
                if ( preg_match( '/^NOSCRIPT/', $conn->getLastError() ) ) {
                        $conn->clearLastError();
                        $res = $conn->eval( $script, $params, $numKeys );
                        wfDebugLog( 'redis', "Used eval() for Lua script $sha1." );
                }

                if ( $conn->getLastError() ) { // script bug?
                        wfDebugLog( 'redis', "Lua script error on server $server: " . $conn->getLastError() );
                }

                $this->lastError = $conn->getLastError() ?: $this->lastError;

                return $res;
        }

        /**
         * @param Redis $conn
         * @return bool
         */
        public function isConnIdentical( Redis $conn ) {
                return $this->conn === $conn;
        }

        function __destruct() {
                $this->pool->freeConnection( $this->server, $this->conn );
        }
}