redis-classy

Redis Classy

A very simple, class-based namespace prefixing and encapsulation for Redis. Key features include:

• Establishes a maintainable convention by prefixing keys with the class name (e.g. YourClass:123)
• Delegates all method calls to the redis-rb within the namespace
• Adds a better abstraction layer around Redis objects and commands

Here's an example:

class Timer < RedisClassy
  def start
    pipelined do
      set Time.now.to_i
      expire 120.seconds
    end
  end

  def stop
    del
  end

  def running?
    !!get
  end
end

timer = Timer.new(123)
timer.start
timer.running?
=> true

Timer.keys
=> ["123"]
RedisClassy.keys
=> ["Timer:123"]

The Timer class above is self-contained and more readable.

This library is made intentionally small, yet powerful when you need better abstraction on Redis objects to keep things organized.

UPGRADING FROM v1

An important message about upgrading from 1.x

redis-rb vs redis-namespace vs redis-classy

With the vanilla redis gem, you've been doing this:

redis = Redis.new
redis.set 'foo', 'bar'
redis.get 'foo'                 # => "bar"

With the redis-namespace gem, you can add a prefix in the following manner:

redis_ns = Redis::Namespace.new('ns', :redis => redis)
redis_ns['foo'] = 'bar'         # equivalent of => redis.set 'ns:foo', 'bar'
redis_ns['foo']                 # => "bar"

Now, with the redis-classy gem, you finally achieve a class-based naming convention:

class Something < RedisClassy
end

Something.on('foo').set('bar')  # equivalent of => redis.set 'Something:foo', 'bar'
Something.on('foo').get         # => "bar"

something = Something.new('foo')
something.set 'bar'             # equivalent of => redis.set 'Something:foo', 'bar'
something.get                   # => "bar"

Usage

In Gemfile:

gem 'redis-classy'

Register the Redis server: (e.g. in config/initializers/redis_classy.rb for Rails)

RedisClassy.redis = Redis.current

Create a class that inherits RedisClassy. (e.g. in app/redis/cache.rb for Rails, for auto- and eager-loading)

class Cache < RedisClassy
  def put(content)
    pipelined do
      set content
      expire 5.seconds
    end
  end
end

cache = Cache.new(123)
cache.put "This tape will self-destruct in five seconds. Good luck."

Since the on method is added as a syntactic sugar for new, you can also run a command in one shot as well:

Cache.on(123).persist

For convenience, singleton and predefined static keys are also supported.

class Counter < RedisClassy
  singleton
end

Counter.incr    # 'Counter:singleton' => '1'
Counter.incr    # 'Counter:singleton' => '2'
Counter.get     # => '2'

class Stats < RedisClassy
  singletons :median, :average
end

ages = [21,22,24,28,30]

Stats.median.set  ages[ages.size/2]           # 'Stats:median'  => '24'
Stats.average.set ages.inject(:+)/ages.size   # 'Stats:average' => '25'
Stats.median.get    # => '24'
Stats.average.get   # => '25'

Finally, you can also pass an arbitrary object that responds to id as a key. This is useful when used in combination with ActiveRecord, etc.

class Lock < RedisClassy
end

class Room < ActiveRecord::Base
end

room = Room.create

lock = Lock.new(room)

When you need an access to the non-namespaced, raw Redis keys, it's available as RedisClass.keys. Keep in mind that this method is very slow at O(N) computational complexity and potentially hazardous when you have many keys. Read the details.

RedisClassy.keys
=> ["Stats:median", "Stats:average", "Counter"]

RedisClassy.keys 'Stats:*'
=> ["Stats:median", "Stats:average"]

Since the redis attribute is a class instance variable, you can dynamically assign different databases for each class, without affecting other classes.

Cache.redis = Redis::Namespace.new('Cache', redis: Redis.new(host: 'another.host'))

Unicorn support

If you run fork-based app servers such as Unicorn or Passenger, you need to reconnect to the Redis after forking.

after_fork do
  RedisClassy.redis.client.reconnect
end

Note that since Redis Classy assigns a namespaced Redis instance upon the inheritance event of each subclass (class Something < RedisClassy), reconnecting the master (non-namespaced) connection that is referenced from all subclasses should probably be the safest and the most efficient way to survive a forking event.

Reference

Dependency:

• https://github.com/ezmobius/redis-rb
• https://github.com/defunkt/redis-namespace

Use case:

• https://github.com/kenn/redis-mutex