redis_support

Redis Support

redis_support is a small library which provides simple support for common actions for the Redis key-value store. It is not an object-relational mapper, does not attempt to comprehensively solve all of your storage problems, and does not make julienne fries.

Redis Addition

Provides a connection to redis which is the same across all classes which use RedisSupport as a mixin. This connection can be set by calling, for example:

RedisSupport.redis = "localhost:6379"

Key Support

Redis provides a global keyspace. Most projects specify their keys using namespaces delimited by colons (:), with variables mixed in at particular points. For example:

users:1:email

redis_support, when used as a mixin, will provide a simple method to declare that namespace and access it later.

class User
  include RedisSupport
  redis_key :email, "users:USER_ID:email"

  attr_accessor :id

  def email
    redis.get Keys.email( self.id )
  end
end

Helpful exceptions are raised if you try to declare the same namespace twice - RedisSupport keeps track of all the key definitions your app wants to use.

Locking Support

There is also a simple locking mechanism based on SETNX. Locking is usually unnecessary since Redis operations are atomic and Redis' MULTI/EXEC/DISCARD gives you the ability to make multiple operations atomic. But sometimes it's useful - a contrived example - major_operation will block for up to 30 seconds if another process attempts to run it at the same time:

class User
  include RedisSupport
  redis_key :email, "users:USER_ID:email"

  attr_accessor :id

  def major_operation
    redis_lock Keys.email( self.id ) do
      # do my expensive stuff
    end
  end
end

Issues

• When RedisSupport.redis is called but not yet set, there is a stack-level too deep error though it should just return nil.