Class: RedisExpLock

Inherits:
Object
  • Object
show all
Defined in:
lib/redis_exp_lock.rb,
lib/redis_exp_lock/version.rb

Defined Under Namespace

Classes: AlreadyAcquiredLockError, TooManyLockAttemptsError

Constant Summary collapse

LUA = 
{
  # Deletes keys if they equal the given values
  :delequal => """
    local deleted = 0
    if redis.call('GET', KEYS[1]) == ARGV[1] then
      return redis.call('DEL', KEYS[1])
    end
    return 0
  """,
}
VERSION = 
'0.1.1'

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(lock_key, opts) ⇒ RedisExpLock

Returns a new instance of RedisExpLock.

Raises:

  • (ArgumentError) 


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# File 'lib/redis_exp_lock.rb', line 22

def initialize(lock_key, opts)
  defaults = {
    :expiry => nil, # in seconds
    :retries => 0,
    :retry_interval => 0.01, # in seconds
  }
  opts = {}.merge(defaults).merge(opts)

  @lock_key = lock_key.to_s
  raise ArgumentError.new('Invalid lock key') unless @lock_key.size > 0
  @lock_uuid = nil

  @redis = opts[:redis]
  @shavaluator = Shavaluator.new(:redis => @redis)
  @shavaluator.add(LUA)

  @expiry = opts[:expiry]
  @retries = opts[:retries]
  @retry_interval = opts[:retry_interval]
end

Instance Attribute Details

#expiry ⇒ Object (readonly)

Returns the value of attribute expiry.



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# File 'lib/redis_exp_lock.rb', line 20

def expiry
  @expiry
end

#lock_key ⇒ Object (readonly)

Returns the value of attribute lock_key.



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# File 'lib/redis_exp_lock.rb', line 20

def lock_key
  @lock_key
end

#lock_uuid ⇒ Object (readonly)

Returns the value of attribute lock_uuid.



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# File 'lib/redis_exp_lock.rb', line 20

def lock_uuid
  @lock_uuid
end

#redis ⇒ Object (readonly)

Returns the value of attribute redis.



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# File 'lib/redis_exp_lock.rb', line 20

def redis
  @redis
end

#retries ⇒ Object (readonly)

Returns the value of attribute retries.



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# File 'lib/redis_exp_lock.rb', line 20

def retries
  @retries
end

#retry_interval ⇒ Object (readonly)

Returns the value of attribute retry_interval.



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# File 'lib/redis_exp_lock.rb', line 20

def retry_interval
  @retry_interval
end

Instance Method Details

#key_locked? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/redis_exp_lock.rb', line 47

def key_locked?
  @redis.exists(@lock_key)
end

#key_owned? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/redis_exp_lock.rb', line 51

def key_owned?
  !@lock_uuid.nil? && @lock_uuid == @redis.get(@lock_key)
end

#lock ⇒ Object

Raises:



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# File 'lib/redis_exp_lock.rb', line 74

def lock
  attempts = 0
  while attempts <= @retries
    attempts += 1
    return attempts if try_lock
    sleep @retry_interval
  end
  raise TooManyLockAttemptsError
end

#locked? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/redis_exp_lock.rb', line 43

def locked?
  !@lock_uuid.nil?
end

#synchronize(&crit_sec) ⇒ Object 



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# File 'lib/redis_exp_lock.rb', line 91

def synchronize(&crit_sec)
  attempts = lock
  crit_sec.call attempts
  unlock
end

#try_lock ⇒ Object

Attempt to acquire the lock, returning true if the lock was succesfully acquired, and false if not.

Raises:



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# File 'lib/redis_exp_lock.rb', line 57

def try_lock
  raise AlreadyAcquiredLockError if locked?

  uuid = SecureRandom.uuid
  set_opts = {
    :nx => true
  }
  set_opts[:px] = Integer(@expiry * 1000) if @expiry

  if @redis.set(@lock_key, uuid, set_opts)
    @lock_uuid = uuid
    true
  else
    false
  end
end

#unlock ⇒ Object 



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# File 'lib/redis_exp_lock.rb', line 84

def unlock
  return false unless locked?
  was_locked = @shavaluator.exec(:delequal, :keys => [@lock_key], :argv => [@lock_uuid]) == 1
  @lock_uuid = nil
  was_locked
end