Redis

Redis is an open-source, networked, in-memory, key-value data store with optional durability, written in ANSI C.

SetupEdit

CacheEdit

If you have not already, you'll need to configure a Redis instance and install a Redis client library for PHP. Most environments require the phpredis PHP extension. On Debian / Ubuntu, you can install the requirements with the following command:

apt-get install redis-server php-redis

In your "LocalSettings.php" file, set:

$wgObjectCaches['redis'] = [
    'class'                => 'RedisBagOStuff',
    'servers'              => [ '127.0.0.1:6379' ],
    // 'connectTimeout'    => 1,
    // 'persistent'        => false,
    // 'password'          => 'secret',
    // 'automaticFailOver' => true,
];
Parameters explained
  • servers: An array of server names. A server name may be a hostname, a hostname/port combination or the absolute path of a UNIX socket. If a hostname is specified but no port, the standard port number 6379 will be used. Arrays keys can be used to specify the tag to hash on in place of the host/port. Required.
  • connectTimeout: The timeout for new connections, in seconds. 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.
  • automaticFailover: If this is false, then each key will be mapped to a single server, and if that server is down, any requests for that key will fail. If this is true, a connection failure will cause the client to immediately try the next server in the list (as determined by a consistent hashing algorithm). True by default. This has the potential to create consistency issues if a server is slow enough to flap, for example if it is in swap death. True by default.

You will now be able to acquire a Redis object cache object via wfGetCache( 'redis' ). If you'd like to use Redis as the default cache for various data, you may set any of the following configuration options:

$wgMainCacheType = 'redis';
$wgSessionCacheType = 'redis';

// Not widely tested
$wgMessageCacheType = 'redis';
$wgParserCacheType = 'redis';
$wgLanguageConverterCacheType = 'redis';

Job queueEdit

$wgJobTypeConf['default'] = [
    'class'          => 'JobQueueRedis',
    'redisServer'    => '127.0.0.1:6379',
    'redisConfig'    => [],
    'claimTTL'       => 3600,
    'daemonized'     => true
 ];
Parameters explained
  • redisConfig: An array of parameters to RedisConnectionPool::__construct(). Note that the serializer option is ignored as "none" is always used. If the same Redis server is used as for $wgObjectCaches, the Redis password needs to be set here as well (see $wgObjectCaches config above).
  • redisServer: A hostname/port combination or the absolute path of a UNIX socket. If a hostname is specified but no port, the standard port number 6379 will be used. Required.
  • compression: The type of compression to use; one of (none,gzip).
  • daemonized: Currently it doesn't support setting it to false.

From that moment, jobs will be delivered to the Redis instance on the specified server.

Automatic handling of job recycling and abandonsEdit

Abandoned jobs aren't purged from redis, and failed and delayed jobs need to be rescheduled. This requires a special job runner service.

Clone the git repository https://github.com/wikimedia/mediawiki-services-jobrunner

Create a configuration file named config.json:

{
        "groups": {
                "basic": {
                        "runners": 0
                }
        },
        "limits": {
        },
        "redis": {
                "aggregators": [
                        "127.0.0.1:6379"
                ],
                "queues": [
                        "127.0.0.1:6379"
                ]
        },
        "dispatcher": "nothing"
}

Configure a daemon to run this at server start:

php redisJobChronService --config-file=config.json

The daemon itself supports running jobs from the queue, but that's not very well documented.

MediaWiki & Wikimedia use cases for RedisEdit

Further readingEdit

GeneralEdit

AnalyticsEdit

ToolingEdit

Informed OpinionsEdit

MiscellaneousEdit