$redis global variable with ruby on rails

I am using redis as a read cache. I have created an initializer

config/initializer/redis.rb

$redis = Redis.new(:host => ENV["REDIS_HOST"], :port => ENV["REDIS_PORT"])

I am using this global in my unicorn.rb to create a new connection whenever a new worker is created.

before_fork do |server, worker|
# clear redis connection
$redis.quit unless $redis.blank?
end

# Give each child process its own Redis connection
after_fork do |server, worker|
$redis = Redis.new(:host => ENV["REDIS_HOST"], :port => ENV["REDIS_PORT"])
end

I am also using this global variable whenever I need to access my redis servers. But I am not comfortable using this global variable. Are there any better options than using global variable?

There is `Redis.current`, which you can use to store your one-and-only `Redis` instance.

So instead of using `$redis`, you can assign your instance as follows:

Redis.current = Redis.new(:host => ENV["REDIS_HOST"], :port => ENV["REDIS_PORT"])

`Redis.current` was [introduced to redis-rb in 2010](

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) as a standard way to grab a redis connection, so I was surprised that no other answer mentioned it.

**Update:** Starting with version 4.6.0 `Redis.current` [has been deprecated](

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). The author notes that typical multi-threaded applications will find a lot of locking around a shared redis client. They recommend to define an own place to get a redis client, but also suggest to use a connection pool.

The accepted answer is therefore the simplest solution to achieve something comparable to `Redis.current`, but may not perform optimal in multi-threaded environments.

expanding further on mestachs suggestion, namespacing a module in your initializer as below

config/initializers/redis.rb

module ReadCache
class << self
def redis
@redis ||= Redis.new(:url => (ENV["REDIS_URL"] || 'redis://127.0.0.1:6379'))
end
end
end

then in unicorn.rb

before_fork do |server, worker|
...
if defined?(ReadCache.redis)
ReadCache.redis.quit
end
...
end

after_fork do |server, worker|
...
if defined?(ReadCache.redis)
ReadCache.redis.client.reconnect
end
...
end

According to [this](

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) Heroku, you don't need to add `$redis` to your Unicorn:
> No special setup is required when using Redis Cloud with a Unicorn server. Users running Rails apps on Unicorn should follow the instructions in the [Configuring Redis from Rails](

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) section and users...

Here's all the "[Configuring Redis from Rails](

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) section" has for before Rails 4 (besides the Gemfile and some other pre-Rails 3 stuff):

# config/initalizers/redis.rb

if ENV["REDISCLOUD_URL"]
uri = URI.parse(ENV["REDISCLOUD_URL"])
$redis = Redis.new(:host => uri.host, :port => uri.port, :password => uri.password)
end

It doesn't really give an explanation as to why "no special setup is required".

try this out:-

you can use `constant` instead of `global variable`.like in
config/initializer/redis.rb

REDIS = Redis.new(:host => ENV["REDIS_HOST"], :port => ENV["REDIS_PORT"])

and in unicorn.rb

before_fork do |server, worker|
# clear redis connection
REDIS.quit if defined?(REDIS)
end

# Give each child process its own Redis connection

after_fork do |server, worker|
REDIS ||= Redis.new(:host => ENV["REDIS_HOST"], :port => ENV["REDIS_PORT"])
end

A more **namespaced** option to replace your global variable, you can create a method in a module

<pre>
module Caching
def self.redis
... initialize/memoize/reconnect here...
end
end
</pre>

You than then call it with:

```
Caching.redis
```

if you don't already use another Rails.cache I advise you to just use that mechanism with redis.

The gem redis-store makes this realy easy (

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)

This way you can just do `Rails.cache.reconnect` and all is dandy

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It also allows you to use the awesome Rails.cache API, which has some neat features:

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