EventCore - General Purpose Main Loop for Ruby

Travis CI Status:

Provides the core of a fully asynchronous application. Modeled for simplicity and robustness, less so for super high load or real time environments. Reservations aside, EventCore should still easily provide low enough latency and high enough throughput for most applications.

Features:

Timeouts.
Fire-once events.
Fire-repeatedly events.
Thread safety.
Simple idiom for integrating with external threads.
Unix signals dispatched on the main loop to avoid the dreaded "trap context".
Core is parked in a select() when the loop is idle to incur negligible load on the system.
Async process controls - aka Process.spawn() with callbacks on the main loop thread and automatic reaping of children.

EventCore is heavily inspired by the proven architecture of the GLib main loop from the GNOME project. Familiarity with that API should not be required though, the EventCore API is small an easy to learn.

Examples

Do something every 200ms for 3s then quit:

require 'event_core'
loop = EventCore::MainLoop.new
loop.add_timeout(0.2) { puts 'Something' }
loop.add_once(3.0) { puts 'Quitting'; loop.quit }
loop.run
puts 'Done'

Sit idle and print the names of the signals it receives:

...
loop.add_unix_signal('HUP', 'USR1', 'USR2') { |signals|
  puts "Got signals: #{signals.map { |signo| Signal.signame(signo) } }"

}

puts "Kill me with PID #{Process.pid}, fx 'kill -HUP #{Process.pid}'"
loop.run
puts 'Done'

Spin off a child process and get a callback in the main loop when it terminates:

...
loop.spawn("sleep 10") { |status|
  puts "Child process terminated: #{status}"
}

(Note - loop.spawn accepts all the same parameters as convential Ruby Process.spawn. Also the status argument is a Process::Status like $?)

Do something on the main loop when a long running thread detects there is work to do:

require 'thread'
...

thr = Thread.new {
  sleep 5 # Working hard! Or hardly working, eh!?
  loop.add_once { puts 'Yay! Back on the main loop' }
  sleep 5
  loop.add_once { puts 'I quit!'; loop.quit }
}

loop.run
thr.join
puts 'All done'

Do something repeatedly on each loop iteration, 10 times:

...
i = 0
loop.add_idle {
    i += 1
    puts "Count #{i}"
    next false if i == 10
}

Concepts and Architecture

TODO, mainloop, sources, triggers, idles, timeouts, select io

Caveats & Known Bugs

If you use multiple main loops on different threads the reaping of child processes using the async spawn is currently broken
Unix signal handlers, for the same signal, between two main loops (in the same process) will clobber each other
Unlike GMainLoop, EventCore does not have a concept of priority. All sources on the main loop have equal priority.
MainLoop.spawn does not work in JRuby (other than 9k, which should be ok). This is not likely to be fixable; see jruby/jruby#2684

FAQ

Can I have several main loops in the same process Yes, but see caveat above, wrt unix signals and loop.spawn()

kasperlanger/event_core

EventCore - General Purpose Main Loop for Ruby

Examples

Concepts and Architecture

Caveats & Known Bugs

FAQ