From: Paul Brannan <pbrannan@...>
Date: 2002-06-25T02:25:11+09:00
Subject: Re: detecting a socket dropping in multi-threaded app

> Firestone, Mark - Technical Support (mark.firestone@gossgraphic.co.uk) wrote:
> > How about this?  My @who data structure is shared with a mutex between the
> > threads.  It keeps a list of the thread id with each person's username and
> > whatever who is logged on.  When someone hangs up, Ruby just kills the
> > thread (I verified this with an experiment last night...)
> > 
> > I write a thread that wakes up every so often and checks Thread.current, and
> > compares that list with the list in @who, and if someone is missing from
> > Thread.current, zaps them from the list.
> > 
> > Is this a reasonable idea?

Why not wrap your thread with an ensure block that removes the person
from the list when it is executed?

  t = Thread.new do
    # add the person to the list
    begin
      loop do
        # Your logic here; when the socket (or other IO object) goes
        # away, break out of the loop.
      end
    ensure
      # remove the person from the list
    end
  end

This reduces possibility for reading from a socket that isn't there, or
for doing something for a user who isn't logged in.

(I never received the original message, btw, so I'm not 100% sure I
understand exactly what the problem is).

Paul