Contents

= Redis Mutex

Distrubuted non-blocking mutex in Ruby using Redis.

The idea was taken from - http://redis.io/commands/setnx and http://gist.github.com/457269

Requires the redis-classy gem.

== Install

 gem install redis-mutex

== Usage

In Gemfile:

 gem "redis-mutex"

In config/initializers/redis_mutex.rb:

 Redis::Classy.db = Redis.new(:host => 'localhost')

There are four methods - new, lock, unlock and sweep:

 mutex = Redis::Classy::Mutex.new(some_object)
 mutex.lock
 mutex.unlock
 Redis::Classy::Mutex.sweep

It takes any Ruby objects that respond to :id, where the key is automatically set as "TheClass:id", or pass any string as a key.

Here's a sample usage in a Rails app:

 class RoomController < ApplicationController
   def enter
     @room = Room.find_by_id(params[:id])
     
     mutex = Redis::Classy::Mutex.new(@room)   # key => "Room:123"
     
     if mutex.lock    # return true when you successfully obtain the lock for the room 123
       ...
       do_something
       ...
       mutex.unlock   # exit the critical section ASAP
     end
   end
 end

The caveat is that the lock just returns false when it fails and do not block.

If you take a closer look, you find that the actual key is structured in the following form:

 Redis::Classy.keys
 => ["Redis::Classy::Mutex:Room:123"]

For more internal details, refer to https://github.com/kenn/redis-classy

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
redis-mutex-0.9.0	README.rdoc