Is Redis connection shared in Rails?

Question

In my Rails app I have an initializer that creates a Redis connection:

$redis = Redis.new(:host => 'localhost', :port => 6379, :db => 3)

My question is: is this connection shared for all workers for this app, or does each worker thread create its own connection everytime I use $redis?

Answer 1

You can try using gem connection_pool , which is generic pool for any network client.

Gemfile:

gem 'connection_pool'

initializers/redis.rb:

require 'connection_pool'

conf = YAML.load(File.read(File.join('config','redis.yml')))
redis_config = conf[Rails.env.to_s]

Redis.current = ConnectionPool.new(size: 10, timeout: 5) do 
  Redis.new host: redis_config['host'], port: redis_config['port'], db: redis_config['db']
end

config/redis.yml

development:
  host: localhost
  port: 6379
  db: 0
test:
  host: localhost
  port: 6379
  db: 15
production:
  host: localhost
  port: 6379
  db: 0

Then later, in your code:

Redis.current.with do |conn|
  value = conn.get('foo')
  conn.sadd('bar', 1)
end

Inside the with block, conn will contains a Redis object from the pool. It will be returned to the pool when the block exits, either normally or because an exception was thrown.