Class: Cash::Lock

Inherits:
Object
  • Object
show all
Defined in:
lib/cash/lock.rb

Defined Under Namespace

Classes: Error

Constant Summary collapse

INITIAL_WAIT = 
2
DEFAULT_RETRY = 
8
DEFAULT_EXPIRY = 
30

Instance Method Summary collapse

Constructor Details

#initialize(cache) ⇒ Lock

Returns a new instance of Lock.



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# File 'lib/cash/lock.rb', line 11

def initialize(cache)
  @cache = cache
end

Instance Method Details

#acquire_lock(key, lock_expiry = DEFAULT_EXPIRY, retries = DEFAULT_RETRY, initial_wait = INITIAL_WAIT) ⇒ Object

Raises:



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# File 'lib/cash/lock.rb', line 28

def acquire_lock(key, lock_expiry = DEFAULT_EXPIRY, retries = DEFAULT_RETRY, initial_wait = INITIAL_WAIT)
  retries.times do |count|
    response = @cache.add("lock/#{key}", host_pid, lock_expiry)
    return if response == "STORED\r\n"
    return if recursive_lock?(key)
    exponential_sleep(count, initial_wait) unless count == retries - 1
  end
  debug_lock(key)
  raise Error, "Couldn't acquire memcache lock on #{@cache.get_server_for_key("lock/#{key}")}"
end

#exponential_sleep(count, initial_wait) ⇒ Object 



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# File 'lib/cash/lock.rb', line 43

def exponential_sleep(count, initial_wait)
  sleep((2**count) / initial_wait)
end

#release_lock(key) ⇒ Object 



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# File 'lib/cash/lock.rb', line 39

def release_lock(key)
  @cache.delete("lock/#{key}")
end

#synchronize(key, lock_expiry = DEFAULT_EXPIRY, retries = DEFAULT_RETRY, initial_wait = INITIAL_WAIT) ⇒ Object 



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# File 'lib/cash/lock.rb', line 15

def synchronize(key, lock_expiry = DEFAULT_EXPIRY, retries = DEFAULT_RETRY, initial_wait = INITIAL_WAIT)
  if recursive_lock?(key)
    yield
  else
    acquire_lock(key, lock_expiry, retries, initial_wait)
    begin
      yield
    ensure
      release_lock(key)
    end
  end
end