Simple Redis Lock

Simple and fast lock using one single redis call of 'SET k v NX EX' It is non blocking, meaning that if you cannot acquire the lock, the given block will not be executed.

While the alternatives are awesome, I wanted a simple solution, kind of 5 lines of code, and a simple single redis solution.

This is the code of the gem, nice and knit:

if @redis.set(key, Time.now, nx: true, px: timeout)
  begin
    yield
  ensure
    @redis.del key
  end
end

And here is a more extensive usage:

simple_lock = SimpleRedisLock.create(Redis.new) # or just SimpleRedisLock.create
Thread.new do
  simple_lock.lock('task_384', 10) do
    sleep 0.100
    # Run critical code section...
    'return value'
  end # => 'return value'
end
sleep 0.001 # wait for threads to sync
simple_lock.acquired_at('task_384') # => 2016-10-12 03:25:19.287 +0300
simple_lock.ttl('task_384') # => 9.989 # remainging seconds
simple_lock.lock('task_384', 10) # => nil # lock is still held.
sleep 0.100 # wait for block to completed and release lock

# block execution completed, lock released.
simple_lock.lock('task_384', 0.100) # => true, no block given, expecting it to expire in 100ms even if not released.
simple_lock.lock('task_384', 10) # => nil # cannot acquire lock, it is still held
sleep 0.100 # wait for expiration to pass

# Expiration passed, lock released
simple_lock.lock('task_384', 10) # => true
# Run critical code section...
simple_lock.release('task_384')
simple_lock.acquired_at('task_384') # => nil
simple_lock.ttl('task_384') # => nil

Installation

Add this line to your application's Gemfile:

gem 'simple_redis_lock'

And then execute:

$ bundle

Or install it yourself as:

$ gem install simple_redis_lock

Alternatives:

I explored some other awesome alternatives before creating this gem:

but they had too many features of blocking to acquire lock and didn't use this single SET KEY 1 NX EX 3600 awesome atomic redis statement.