Asp Forum - Issue with threads and socket accept

Vasyl Smirnov

12/11/2007 4:18:00 PM

Hi,

I'm writing a multi-threaded server, and would like to stop it on a
signal (SIGINT on Ctrl-C in this case).
The problem is that after the first connection is accepted, and then
Ctrl-C is hit, the "while accept" loop doesn't break. If you hit Ctrl-
C before any connections, it just works fine. And the single-threaded
version, of course, works
as well.

Could somebody explain what am I doing wrong?

Below is a simple application that reproduces the problem. Change the
last line to "server.serve_seq" to run a single-threaded version.

Thanks in advance!

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

require 'socket'

class MyServer
def initialize
@servsock = TCPServer.new("127.0.0.1", 1111)
end

def work(sock)
begin
lines = 0
lines += 1 while sock.gets
puts "Got #{lines} lines."
rescue Exception => e
print "exception: "; p e
ensure
sock.close
end
end

def serve_mt
while clisock = @servsock.accept
Thread.new(clisock) { |sock| work(sock) }
end
end

def serve_seq
while sock = @servsock.accept
work(sock)
end
end

def shutdown
return nil if @servsock.nil? or @servsock.closed?
puts "Shutting down..."
@servsock.close
end
end

server = MyServer.new
Signal.trap("INT") { server.shutdown }
server.serve_mt

5 Answers

Curt Sampson

12/11/2007 5:44:00 PM

On 2007-12-12 01:18 +0900 (Wed), Vasyl Smirnov wrote:

> I'm writing a multi-threaded server, and would like to stop it on a
> signal (SIGINT on Ctrl-C in this case).
> The problem is that after the first connection is accepted, and then
> Ctrl-C is hit, the "while accept" loop doesn't break....
> Could somebody explain what am I doing wrong?

Errr..."not investigating deep and strange mysteries of the Ruby interpreter
signal handling that are not comprehensible even after reading the source?"

I hope I get a point for that answer.

But anyway, much as I'd like to know *why* the signal handling is set up
to ignore signals when waiting in accept(), a situation on which the
source code that does this is particularly silent, I just live with the
solution, which is:

Do a select() before your accept(), and wait until the socket in
question becomes readable.

You and I are not the only ones caught by this, as it happens. The native
Ruby FastCGI code has the same issue.

cjs
--
Curt Sampson <cjs@starling-software.com> +81 90 7737 2974
Mobile sites and software consulting: http://www.starling-so...

Francis Cianfrocca

12/11/2007 5:54:00 PM

Note: parts of this message were removed by the gateway to make it a legal Usenet post.

On Dec 11, 2007 11:18 AM, Vasyl Smirnov <vasyl.smirnov@gmail.com> wrote:

> Hi,
>
> I'm writing a multi-threaded server, and would like to stop it on a
> signal (SIGINT on Ctrl-C in this case).
> The problem is that after the first connection is accepted, and then
> Ctrl-C is hit, the "while accept" loop doesn't break. If you hit Ctrl-
> C before any connections, it just works fine. And the single-threaded
> version, of course, works
> as well.
>
> Could somebody explain what am I doing wrong?
>

Without addressing your specific question, let me suggest that you
investigate the Ruby/Eventmachine library. It should make your application
easier to develop.

Vasyl Smirnov

12/11/2007 6:25:00 PM

On Dec 11, 7:53 pm, "Francis Cianfrocca" <garbageca...@gmail.com>
wrote:
> Without addressing your specific question, let me suggest that you
> investigate the Ruby/Eventmachine library. It should make your application
> easier to develop.

Thanks, Francis, I'm just reading the docs for your library!

Vasyl Smirnov

12/11/2007 6:27:00 PM

On Dec 11, 7:43 pm, Curt Sampson <c...@cynic.net> wrote:
> Errr..."not investigating deep and strange mysteries of the Ruby interpreter
> signal handling that are not comprehensible even after reading the source?"
>
> I hope I get a point for that answer.

You probably do :)

> But anyway, much as I'd like to know *why* the signal handling is set up
> to ignore signals when waiting in accept(), a situation on which the
> source code that does this is particularly silent, I just live with the
> solution, which is:

Well, actually the signal handler gets called, it calls shutdown,
outputs a message
to the stdout and closes the server socket. And the main thread is
still inside accept.

> Do a select() before your accept(), and wait until the socket in
> question becomes readable.

I've tried this, with the same success:

def serve_mt2
until @servsock.closed?
IO.select([@servsock])
clisock = @servsock.accept
Thread.new(clisock) { |sock| work(sock) }
end
end

Robin

6/5/2008 3:08:00 PM

On Jun 5, 8:09 am, "Pieter" <hrdou...@zonnet.nl> wrote:
> "MikeRyder" <n...@nospam.com> schreef in berichtnews:o07e44dnsms3hfqvuon2icfrh1ehrorqot@4ax.com...
>
> > On Wed, 4 Jun 2008 15:39:39 -0700 (PDT), george
> > <georgeculol...@hotmail.com> wrote:
> >>I can choose to see the sinlessness of everyone.
>
> > How about their actions.
>
> > Back to ol' Hitler again. Or...how about bin laden. How do you
> > perceive his actions?
>
> Jesus speaks in the Course of
> "appalling errors", and says of the
> perpetrators: "Father, forgive them
> for they know not what they do."
> Moreover, he says that we are not
> guiltless in time, but in eternity.
>
> "Time seems to go in one direction, but when you
> reach its end, it will roll up like a long carpet that
> has spread along the past behind you, and will
> disappear. As long as you believe the Son of God
> is guilty, you will walk along this carpet, believing
> that it leads to death. And the journey will seem
> long and cruel and senseless, for so it is." (1800; T-13.I.5:5-7)

Yes Bush just as crazy as bin laden, but he has the people of American
to make his atrocities ok...

comp.lang.ruby

Issue with threads and socket accept

Vasyl Smirnov

Curt Sampson

Francis Cianfrocca

Vasyl Smirnov

Vasyl Smirnov

Robin

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