Module: Redislock

Defined in:
lib/redislock.rb,
lib/redislock/version.rb

Defined Under Namespace

Classes: Error, Lock

Constant Summary collapse

VERSION = 
"0.9.0"

Class Method Summary collapse

Class Method Details

.aquire(name, seconds, &block) ⇒ Object 



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# File 'lib/redislock.rb', line 18

def self.aquire(name, seconds, &block)    
  current = Speedytime.current
  expiry = current + seconds + 1
  key = "lock.#{name}"

  # Try to aquire the lock, if we can do this 
  # we can simply execute the block with the 
  # help of the Lock strucutre
  if Redislock.redis.setnx(key, expiry)
    return Lock.new(key, &block).call
  end

  # we didn't get the lock, lets see if there is a deadlock
  # that we can resolve via an expired lock
  upstream_value = Redislock.redis.get(key)
  if upstream_value.to_i < current
    # ok we are expired. Let's see if we can aquire this 
    #
    # Note, there are likely multiple processes competing 
    # to aquire this lock, therefore we have to use 
    # atomic primitives here to avoid mistakes 

    if Redislock.redis.getset(key, expiry) == upstream_value
      return Lock.new(key, &block).call 
    end
  end

  # in all other cases we fail to aquire the lock 
  return false
end

.redis ⇒ Object 



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# File 'lib/redislock.rb', line 14

def self.redis
  @redis || raise(Error, "Please set Redislock.redis before using this class")
end

.redis=(redis) ⇒ Object 



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# File 'lib/redislock.rb', line 10

def self.redis=(redis)
  @redis = redis
end