PHPSessionHandler: Implement SessionHandlerInterface

[mediawiki.git] / includes / filebackend / lockmanager / RedisLockManager.php

<?php
/**
 * Version of LockManager based on using redis servers.
 *
 * 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
 * @ingroup LockManager
 */

/**
 * Manage locks using redis servers.
 *
 * Version of LockManager based on using redis servers.
 * This is meant for multi-wiki systems that may share files.
 * All locks are non-blocking, which avoids deadlocks.
 *
 * All lock requests for a resource, identified by a hash string, will map to one
 * bucket. Each bucket maps to one or several peer servers, each running redis.
 * A majority of peers must agree for a lock to be acquired.
 *
 * This class requires Redis 2.6 as it makes use Lua scripts for fast atomic operations.
 *
 * @ingroup LockManager
 * @since 1.22
 */
class RedisLockManager extends QuorumLockManager {
        /** @var array Mapping of lock types to the type actually used */
        protected $lockTypeMap = array(
                self::LOCK_SH => self::LOCK_SH,
                self::LOCK_UW => self::LOCK_SH,
                self::LOCK_EX => self::LOCK_EX
        );

        /** @var RedisConnectionPool */
        protected $redisPool;

        /** @var array Map server names to hostname/IP and port numbers */
        protected $lockServers = array();

        /** @var string Random UUID */
        protected $session = '';

        /**
         * Construct a new instance from configuration.
         *
         * @param array $config Parameters include:
         *   - lockServers  : Associative array of server names to "<IP>:<port>" strings.
         *   - srvsByBucket : Array of 1-16 consecutive integer keys, starting from 0,
         *                    each having an odd-numbered list of server names (peers) as values.
         *   - redisConfig  : Configuration for RedisConnectionPool::__construct().
         * @throws Exception
         */
        public function __construct( array $config ) {
                parent::__construct( $config );

                $this->lockServers = $config['lockServers'];
                // Sanitize srvsByBucket config to prevent PHP errors
                $this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
                $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive

                $config['redisConfig']['serializer'] = 'none';
                $this->redisPool = RedisConnectionPool::singleton( $config['redisConfig'] );

                $this->session = wfRandomString( 32 );
        }

        protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
                $status = Status::newGood();

                $server = $this->lockServers[$lockSrv];
                $conn = $this->redisPool->getConnection( $server );
                if ( !$conn ) {
                        foreach ( array_merge( array_values( $pathsByType ) ) as $path ) {
                                $status->fatal( 'lockmanager-fail-acquirelock', $path );
                        }

                        return $status;
                }

                $pathsByKey = array(); // (type:hash => path) map
                foreach ( $pathsByType as $type => $paths ) {
                        $typeString = ( $type == LockManager::LOCK_SH ) ? 'SH' : 'EX';
                        foreach ( $paths as $path ) {
                                $pathsByKey[$this->recordKeyForPath( $path, $typeString )] = $path;
                        }
                }

                try {
                        static $script =
<<<LUA
                        local failed = {}
                        -- Load input params (e.g. session, ttl, time of request)
                        local rSession, rTTL, rTime = unpack(ARGV)
                        -- Check that all the locks can be acquired
                        for i,requestKey in ipairs(KEYS) do
                                local _, _, rType, resourceKey = string.find(requestKey,"(%w+):(%w+)$")
                                local keyIsFree = true
                                local currentLocks = redis.call('hKeys',resourceKey)
                                for i,lockKey in ipairs(currentLocks) do
                                        -- Get the type and session of this lock
                                        local _, _, type, session = string.find(lockKey,"(%w+):(%w+)")
                                        -- Check any locks that are not owned by this session
                                        if session ~= rSession then
                                                local lockExpiry = redis.call('hGet',resourceKey,lockKey)
                                                if 1*lockExpiry < 1*rTime then
                                                        -- Lock is stale, so just prune it out
                                                        redis.call('hDel',resourceKey,lockKey)
                                                elseif rType == 'EX' or type == 'EX' then
                                                        keyIsFree = false
                                                        break
                                                end
                                        end
                                end
                                if not keyIsFree then
                                        failed[#failed+1] = requestKey
                                end
                        end
                        -- If all locks could be acquired, then do so
                        if #failed == 0 then
                                for i,requestKey in ipairs(KEYS) do
                                        local _, _, rType, resourceKey = string.find(requestKey,"(%w+):(%w+)$")
                                        redis.call('hSet',resourceKey,rType .. ':' .. rSession,rTime + rTTL)
                                        -- In addition to invalidation logic, be sure to garbage collect
                                        redis.call('expire',resourceKey,rTTL)
                                end
                        end
                        return failed
LUA;
                        $res = $conn->luaEval( $script,
                                array_merge(
                                        array_keys( $pathsByKey ), // KEYS[0], KEYS[1],...,KEYS[N]
                                        array(
                                                $this->session, // ARGV[1]
                                                $this->lockTTL, // ARGV[2]
                                                time() // ARGV[3]
                                        )
                                ),
                                count( $pathsByKey ) # number of first argument(s) that are keys
                        );
                } catch ( RedisException $e ) {
                        $res = false;
                        $this->redisPool->handleError( $conn, $e );
                }

                if ( $res === false ) {
                        foreach ( array_merge( array_values( $pathsByType ) ) as $path ) {
                                $status->fatal( 'lockmanager-fail-acquirelock', $path );
                        }
                } else {
                        foreach ( $res as $key ) {
                                $status->fatal( 'lockmanager-fail-acquirelock', $pathsByKey[$key] );
                        }
                }

                return $status;
        }

        protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
                $status = Status::newGood();

                $server = $this->lockServers[$lockSrv];
                $conn = $this->redisPool->getConnection( $server );
                if ( !$conn ) {
                        foreach ( array_merge( array_values( $pathsByType ) ) as $path ) {
                                $status->fatal( 'lockmanager-fail-releaselock', $path );
                        }

                        return $status;
                }

                $pathsByKey = array(); // (type:hash => path) map
                foreach ( $pathsByType as $type => $paths ) {
                        $typeString = ( $type == LockManager::LOCK_SH ) ? 'SH' : 'EX';
                        foreach ( $paths as $path ) {
                                $pathsByKey[$this->recordKeyForPath( $path, $typeString )] = $path;
                        }
                }

                try {
                        static $script =
<<<LUA
                        local failed = {}
                        -- Load input params (e.g. session)
                        local rSession = unpack(ARGV)
                        for i,requestKey in ipairs(KEYS) do
                                local _, _, rType, resourceKey = string.find(requestKey,"(%w+):(%w+)$")
                                local released = redis.call('hDel',resourceKey,rType .. ':' .. rSession)
                                if released > 0 then
                                        -- Remove the whole structure if it is now empty
                                        if redis.call('hLen',resourceKey) == 0 then
                                                redis.call('del',resourceKey)
                                        end
                                else
                                        failed[#failed+1] = requestKey
                                end
                        end
                        return failed
LUA;
                        $res = $conn->luaEval( $script,
                                array_merge(
                                        array_keys( $pathsByKey ), // KEYS[0], KEYS[1],...,KEYS[N]
                                        array(
                                                $this->session, // ARGV[1]
                                        )
                                ),
                                count( $pathsByKey ) # number of first argument(s) that are keys
                        );
                } catch ( RedisException $e ) {
                        $res = false;
                        $this->redisPool->handleError( $conn, $e );
                }

                if ( $res === false ) {
                        foreach ( array_merge( array_values( $pathsByType ) ) as $path ) {
                                $status->fatal( 'lockmanager-fail-releaselock', $path );
                        }
                } else {
                        foreach ( $res as $key ) {
                                $status->fatal( 'lockmanager-fail-releaselock', $pathsByKey[$key] );
                        }
                }

                return $status;
        }

        protected function releaseAllLocks() {
                return Status::newGood(); // not supported
        }

        protected function isServerUp( $lockSrv ) {
                return (bool)$this->redisPool->getConnection( $this->lockServers[$lockSrv] );
        }

        /**
         * @param string $path
         * @param string $type One of (EX,SH)
         * @return string
         */
        protected function recordKeyForPath( $path, $type ) {
                return implode( ':',
                        array( __CLASS__, 'locks', "$type:" . $this->sha1Base36Absolute( $path ) ) );
        }

        /**
         * Make sure remaining locks get cleared for sanity
         */
        function __destruct() {
                while ( count( $this->locksHeld ) ) {
                        $pathsByType = array();
                        foreach ( $this->locksHeld as $path => $locks ) {
                                foreach ( $locks as $type => $count ) {
                                        $pathsByType[$type][] = $path;
                                }
                        }
                        $this->unlockByType( $pathsByType );
                }
        }
}