Suo

🔒 Distributed semaphores using Memcached or Redis in Ruby.

Suo provides a very performant distributed lock solution using Compare-And-Set (CAS) commands in Memcached, and WATCH/MULTI in Redis.

Installation

Add this line to your application’s Gemfile:

gem 'suo'

Usage

Basic

# Memcached
suo = Suo::Client::Memcached.new(connection: "127.0.0.1:11211")

# Redis
suo = Suo::Client::Redis.new(connection: {host: "10.0.1.1"})

# Pre-existing client
suo = Suo::Client::Memcached.new(client: some_dalli_client)

suo.lock("some_key") do
  # critical code here
  @puppies.pet!
end

Thread.new { suo.lock("other_key", 2) { puts "One"; sleep 2 } }
Thread.new { suo.lock("other_key", 2) { puts "Two"; sleep 2 } }
Thread.new { suo.lock("other_key", 2) { puts "Three" } }

# will print "One" "Two", but not "Three", as there are only 2 resources

# custom acquisition timeouts (time to acquire)
suo = Suo::Client::Memcached.new(client: some_dalli_client, acquisition_timeout: 1) # in seconds

# manually locking/unlocking
suo.lock("a_key")
foo.baz!
suo.unlock("a_key")

# custom stale lock cleanup (cleaning of dead clients)
suo = Suo::Client::Redis.new(client: some_redis_client, stale_lock_expiration: 60*5)

TODO

• better stale key handling (refresh blocks)
• more race condition tests

History

View the changelog

Contributing

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features