Simple Strategy for Redis in Ruby-on-Rails

Ben Wiseley
February 26, 2012

Simple Strategy for Redis in Ruby-on-Rails

Here’s a simple “it just works” approach to using Redis in your Rails app.

Quick background first. Redis requires a redis-server to be running. A redis-server runs against a port (the default port is 6381). While you can use name-spacing strategies to use the same redis-server for multiple redis db’s it’s not recommended (see KISS principle).

First: Install Redis brew install redis Second: Add to your project Add this to Gemfile gem 'redis' And bundle install Create config/redis/development.conf daemonize yes port 6390 logfile ./log/redis_development.log dbfilename ./db/development.rdb Create config/redis/test.conf daemonize yes port 6391 logfile ./log/redis_test.log dbfilename ./db/test.rdb

These scripts tell redis to start up on port #### - it can be any number but I’d recommend not using 6381 (the default) in case something else is running against that. Redis conf’s can do quite a bit and are worth reading up on before hitting production. Example of a fairly complex redis.conf file

While you can start up redis outside of rails, for simplicity sake, when working with other devs, why not make idiot proof for them? Less in the readme. We do this in this init script Create config/init/redis_init.rb require "redis" redis_conf ="config/redis", "#{Rails.env}.conf")) port = /port.(\d+)/.match(redis_conf)[1] `redis-server #{redis_conf}` res = `ps aux | grep redis-server` unless res.include?("redis-server") && res.include?(redis_conf) raise "Couldn't start redis" end REDIS = => port)

If you’re deploying to Heroku and using redis-to-go - you can use the modified script below. require "redis" if ::Rails.env == "production" uri = URI.parse(ENV["REDISTOGO_URL"]) REDIS = =>, :port => uri.port, :password => uri.password) else redis_conf ="config/redis", "#{Rails.env}.conf")) port = /port.(\d+)/.match(redis_conf)[1] `redis-server #{redis_conf}` res = `ps aux | grep redis-server`

unless res.include?(“redis-server”) && res.include?(redis_conf) raise “Couldn’t start redis” end REDIS = => port) end </code> Now you should be able to fire up bundle exec rails c and see that it’s working by using the REDIS constant irb(main):001:0> REDIS.keys => []