From: Daniel Bush <dlb.id.au@...>
Date: 2009-10-19T21:51:01+09:00
Subject: ruby 1.8.6, threadpooling and blocking sockets - advice/help

Hi,
I think I'm running up against ruby 1.8.6's not so
stellar threading system.  Was hoping someone
could confirm or otherwise point out some flaws.

Note: I get reasonable performance when running on
ruby 1.9 it's just 1.8.6 that hangs like a
deadlock when I start using too many threads in
one of my test scripts.  (My focus is actually
on 1.9 and jruby anyway).

Give you an idea:

I might get a pool of 10 acceptor threads to run
something like the following (each has their own
version of this code):

    client, client_sockaddr = @socket.accept
      # Threads block on #accept.
    data = client.recvfrom( 40 )[0].chomp
    @mutex.synchronize do
      puts "#{Thread.current} received #{data}... "
    end
    client.close

on @socket which was set up like this:

    @socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
    @sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost')
    @socket.bind( @sockaddr )
    @socket.listen( 100 )

I wanted to create a barrage of requests so next I
create a pool of requester threads which each run
something like this:

  socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
  sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
  socket.connect( sockaddr )
  socket.puts "request #{i}"
  socket.close

All of this in one script.  If I have so much as
2 requester threads in addition to the 10
acceptors waiting to receive their requests, 1.8.6
just seizes up before processing anything.  If I
use 2 acceptors and 2 requesters, it works. If I
use 10 acceptors, 1 requester it works.  When it
does work however, it doesn't appear to schedule
threads too well; it just seems to use one all the
time - although this seems to happen only when
using sockets as opposed to a more general job
queue.

I haven't submitted the full code because it uses
a threadpool library I'm still building/reviewing.

Regards,

Daniel Bush
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