memcache_spinlock_sleep_test.rb

require 'rubygems'
require 'memcached'
def sleep_for(count)
  sleep((2**count) / 2.0)
  # sleep (1 / (count + 1).to_f) * 0.6
  # sleep [0.2, (rand / 3)].max
end
class Error < Exception; end
  
def acquire_lock(memcache, key, retries = 100)
  retries.times do |count|
    begin
      response = begin
        memcache.add("#{key}", Process.pid, 10000)
        return true
      rescue Memcached::NotStored
        raise Error if count == retries - 1
      end
    end
    sleep_for(count) unless count == retries - 1
  end
  raise Error, "Couldn't acquire memcache lock for: #{key}"
end


start_time = 0
end_time = 2000
every = 100
duration = 250

memcache = Memcached.new(["localhost:11211"], :namespace => "testing")
start_at = Time.now.to_f + 2
key = "TestKey"
forks = (end_time - start_time) / every
forks.times do |i|
  if fork
  else
    memcache.reset
    my_delay = (every * i) / 1000.0
    sleep((start_at - Time.now.to_f) + my_delay)
    
    begin
      acquire_lock(memcache, key)
    rescue Error
      puts "Failed to acquire lock: #{i}"
      exit
    end
    puts "Acquired lock: #{i}"
    sleep duration / 1000.0
    memcache.delete(key)
    exit
  end
end


Process.waitall
puts "%.5f" % (Time.now.to_f - start_at)