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A binding of epoll(7) on Ruby.

epoll(7) can use Linux only. (because must be installed sys/epoll.h)


require 'epoll'

# Epoll < IO

# Epoll.create
#   call epoll_create(2)
#   it's just alias of `open`
#   Epoll object stock a File Descriptor returned by epoll_create(2)
#   return: instance of Epoll (kind of IO)
epoll = Epoll.create

# IO object add to interest list
#   call epoll_ctl(2)
epoll.add(io, Epoll::IN)  # same way to epoll.ctl(Epoll::CTL_ADD, io, Epoll::IN)

# change waiting events
#   call epoll_ctl(2)
epoll.mod(io, Epoll::OUT) # same way to epoll.ctl(Epoll::CTL_MOD, io, Epoll::OUT)

# remove from interest list
#   call epoll_ctl(2)
epoll.del(io)             # same way to epoll.ctl(Epoll::CTL_DEL, io)

loop do
  # Epoll#wait(timeout=-1)
  #   call epoll_wait(2)
  #   timeout = -1: block until receive event or signals
  #   timeout = 0: return all io's can I/O on non block
  #   timeout > 0: block when timeout pass miri second or receive events or signals
  #   return: Array of Epoll::Event
  evlist = epoll.wait

  # ev is instance of Epoll::Event like `struct epoll_event`
  # it's instance of `class Epoll::Event <, :events); end`
  evlist.each do |ev|
    # Epoll::Event#events is event flag bits (Fixnum)
    if ( & Epoll::IN) != 0
      # Epoll::Event#data is notified IO (IO)
      # e.g. it's expect to I/O readable
    elsif ( & Epoll::HUP|Epoll::ERR) != 0

# you can close File Descriptor for epoll when finish to use
epoll.close #=> nil

# and you can check closed
epoll.closed? #=> true

# and very useful way is that call `create` with block like ``
# return: block result
Epoll.create do |epoll|
  # ensure automatic call `epoll.close` when out block

ctl options

ctl options description
Epoll::CTL_ADD add to interest list for created epoll fd
Epoll::CTL_MOD change io events
Epoll::CTL_DEL delete in interest list

Event flags

event flags ctl wait description
Epoll::IN o o readable
Epoll::PRI o o high priority read
Epoll::HUP o o peer socket was shutdown
Epoll::OUT o o writable
Epoll::ET o x use edge trigger
Epoll::ONESHOT o x auto watching stop when notified(but stay in list)
Epoll::ERR x o raise error
Epoll::HUP x o raise hang up

see also man epoll(7)


Add this line to your application's Gemfile:

gem 'epoll'

And then execute:

$ bundle

Or install it yourself as:

$ gem install epoll

Pro Tips

  • Support call without GVL in CRuby (use rb_thread_call_without_gvl())
  • Close on exec flag set by default if you can use (use epoll_create1(EPOLL_CLOEXEC))
  • Epoll#wait max return array size is 256 on one time (of course, overflowing and then carried next)

Fork Me !

This is experimental implementation. I'm waiting for your idea and Pull Request !


epoll(7) binding in Ruby








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