From: Brian Candler <B.Candler@...>
Date: 2002-11-12T03:48:24+09:00
Subject: Threading in I/O libraries

I'd like to ask: how integrated is threading in Ruby's I/O libraries?

In particular,

(1) if I do a read from a socket, will Ruby call select() first to ensure
that there is data available (to prevent blocking), or do I have to do that
myself?

(2) if I call select() in one thread and no data is available, will this
block the whole Ruby interpreter? Or is it clever: combining all the
select()s from multiple threads and waking them up as their FDs become
ready?

The reason I ask is because I'm thinking of playing with writing a proxy
RADIUS server in Ruby using one of the RADIUS libraries out there. When
forwarding a request, the thread will need to wait for a response before
answering - and if I do a recvfrom() I don't want the whole interpreter to
block :-)

I've had a quick play with TCPServer and it appears to handle threading
correctly - see below - but as there's no UDPServer it looks like I'll have
to get a bit more into the nuts and bolts.

BTW what's the easiest way to tidy up my Testserver below to remove all
those @session.s? If I subclass TCPSocket [the class which server.accept
returns] I still have somehow to convert the object returned by 'accept' to
this new class. I'm sure there's an obvious Ruby Way to do this :-)

Regards,

Brian.


#!/usr/local/bin/ruby -w

class Testserver
  def initialize(session)
    @session = session
  end
  def run
    @session.print "+OK I am a fake POP3 server\n"
    while line = @session.gets
      case line
        when /quit/i
          break
        else
          @session.print "-ERR I don't understand #{line}"
      end
    end
    @session.print "+OK bye\n"
    @session.close
  end
end

require 'socket'
port = (ARGV[0] || 110).to_i
server = TCPServer.new('localhost', port)
while (session = server.accept)
  Thread.new do
    Testserver.new(session).run
  end
end