Class: SuperCache::Lock

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

Defined Under Namespace

Classes: MaxRetriesError

Constant Summary collapse

DEFAULT_RETRY = 
5
DEFAULT_EXPIRY = 
30

Class Method Summary collapse

Class Method Details

.acquire_lock(key, lock_expiry = DEFAULT_EXPIRY) ⇒ Object 



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# File 'lib/super_cache/lock.rb', line 26

def acquire_lock(key, lock_expiry = DEFAULT_EXPIRY)
  Rails.cache.write("lock/#{key}", Process.pid, :unless_exist => true, :expires_in => lock_expiry)
end

.exponential_sleep(count) ⇒ Object 



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# File 'lib/super_cache/lock.rb', line 34

def exponential_sleep(count)
  Benchmark::measure { sleep((2**count) / 5.0) }
end

.release_lock(key) ⇒ Object 



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# File 'lib/super_cache/lock.rb', line 30

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

.synchronize(key, lock_expiry = DEFAULT_EXPIRY, retries = DEFAULT_RETRY) ⇒ Object 



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# File 'lib/super_cache/lock.rb', line 9

def synchronize(key, lock_expiry = DEFAULT_EXPIRY, retries = DEFAULT_RETRY)
  if recursive_lock?(key)
    yield
  else
    begin
      retries.times do |count|
        return yield if acquire_lock(key, lock_expiry)
        raise MaxRetriesError if count == retries - 1
        exponential_sleep(count) unless count == retries - 1
      end
      raise MaxRetriesError, "Couldn't acquire memcache lock for: #{key}"      
    ensure
      release_lock(key)
    end
  end
end