From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-04-07T02:52:24+09:00
Subject: Maximum number of sockets

Hi,

I am trying to test how many concurrent connections a certain web
server (nginx) can support in our machines, so I tried to make a
little ruby script to just open sockets connecting to that machine. I
first increased the fd limit of both the server and the client to
100000 and 50000 respectively, and then did this:

require 'socket'
include Socket::Constants

sockets = []

1086.times do |i|
  print "#{i},"
  socket = Socket.new(AF_INET, SOCK_STREAM, 0)
  sockaddr = Socket.pack_sockaddr_in(80, 'localhost')
  socket.connect(sockaddr)
  sockets << socket
end

print "All sockets connected (#{sockets.size})"
gets

I'm testing first in my own machine both the client and the server
(hence the 'localhost', which shall be replaced by the server IP when
this is ready). I started doing 50000 sockets and I faced a problem:

nginx_client.rb:10: [BUG] Segmentation fault
ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]

(surrounded by all the printed #{i}s)

Testing different numbers, it seems that 1085 works fine, while 1086
crashes. Anybody has any idea why this could be? Am I doing something
wrong in the socket code? Also, I couldn't find a good description of
the sockaddr stuff or the pack_sockaddr_in method: can the result of
pack_sockaddr_in be reused with different sockets?

I'm using the Ubuntu ruby 1.8.7:

Linux jesus-laptop 2.6.27-14-generic #1 SMP Tue Aug 18 16:25:45 UTC
2009 i686 GNU/Linux

ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]

Thanks,

Jesus.