preforker

A gem to easily create prefork servers.

Example

Let’s see an example using the Mac ‘say’ command.

require 'preforker'

#you can open some socket here or reserve any other resource you want to share with your workers, this is master space
Preforker.new(:timeout => 10) do |master|
  #this block is only run from each worker (10 by default)

  #here you should write the code that is needed to be ran each time a fork is created, initializations, etc.
  `say hi`

  #here you could IO.select a socket, run an EventMachine service (see example), or just run worker loop
  #you need to ask master if it wants you alive periodically or else it will kill you after the timeout elapses. Respect your master!
  while master.wants_me_alive? do
    sleep 1
    `say ping pong`
  end

  #here we can do whatever we want when exiting gracefully
  `say bye`
end.start

To kill the server just run:

kill -s QUIT `cat preforker.pid`

See the examples directory and the specs for more examples.

Configuration options

:timeout: The timeout in seconds, 5 by default. If a worker takes more than this it will be killed and respawned.
:workers: Number of workers, 10 by default.
:stdout_path: Path to redirect stdout to. By default it’s /dev/null
:stderr_path: Path to redirect stderr to. By default it’s /dev/null
:app_name: The app name, ‘preforker’ by default. Used for some ps message, log messages messages and pid file name.
:pid_path: The path to the pid file for this server. By default it’s ‘./preforker.pid’.
:logger: This is Logger.new(‘./preforker.log’) by default

Signals

You can send some signals to master to control the way it handles the workers lifetime.

WINCH: Gracefully kill all workers but keep master alive
TTIN: Increase number of workers
TTOU: Decrease number of workers
QUIT: Kill workers and master in a graceful way
TERM, INT: Kill workers and master immediately

Acknowledgments

Most of the preforking operating system tricks come from Unicorn. Check out its source code for a hands on tutorial on Unix internals!

To do list

More tests
Log rotation through the USR1 signal
Have something like min_spare_workers, max_workers

Note on Patches/Pull Requests

Fork the project.
Make your feature addition or bug fix.
Add tests for it. This is important so I don’t break it in a future version unintentionally.
Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
Send me a pull request. Bonus points for topic branches.