Redis

Wikimedia infrastructure

Data centers

Networking

Global traffic routing

MediaWiki

• Application servers
• PHP 7 and php-fpm
• Dumps
• Memcached
• Mcrouter runbook
• Kafka Job Queue
• Nutcracker
• Envoy
• MediaWiki HTTP cache headers
• Redis
• Parser cache
• Statsd
• MediaWiki On Kubernetes
• MediaWiki and EtcdConfig
• Citoid
• Mathoid

Multimedia

Data Engineering

Search

Data Persistence

Infra Foundations

Observability

Performance Team

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For the Redis service at Toolforge, see Nova Resource:Tools/Redis.

Redis is used in Wikimedia production for:

• the MediaWiki job queue
• stashing user sessions ($wgSessionCacheType)
• log messages processed by Logstash

Check puppet and ProductionServices.php for jobqueue_aggregator to see where it runs (as of August 2016 the servers are rdb1001, rdb1003, rdb1005 and rdb1007).

MediaWiki-Vagrant and MediaWiki-Vagrant in Labs are configured by default to use redis for $wgMainCacheType, $wgSessionCacheType, etc.

Usage

Connecting

You can use the redis-cli utility to make queries against redis. In order to make queries against redis, you need to be on a production server such as tin that can access the servers, and give the command

redis-cli -a password-here -h rdb1001

(Grab the password out of /srv/mediawiki/wmf-config/PrivateSettings.php on tin, the server where it runs, look for $wmgRedisPassword in it.)

This will leave you at a redis prompt where you can enter commands interactively.

Some useful commands

info will give you a pile of status information about the server, including the number of keys near the end of the output.

keys pattern-here will give you a list of all keys matching the given pattern. Use this sparingly, there's a lot of keys in there and the query will take (at least) several seconds to complete.

quit closes the connection.

Other references

Commands are easy, they all depend on the data type (hash, set, list, etc). Here's a quick reference.

Configuration is likewise pretty straightforward with perhaps the exception of the snapshotting, aof and memory settings; here's the sample config file.

See also

• memcached
• nutcracker (AKA twemproxy), the proxy used by all application servers to contact memcached (but not redis as of 2015, except it does again as of 2016)