From: Ben Giddings <bg-rubytalk@...>
Date: 2009-09-11T05:48:47+09:00
Subject: Re: Asynchronous http POST?

On Thursday 10 September 2009 15:48:56 Ivan Shevanski wrote:
> Apparently, since control is not returned to the interpreter, when one
> thread waits the other(s) will not continue. At least that's my
> understanding.

A quick test seems to show that isn't the case.  I wrote a simple webrick 
servlet that accepts a post request and delays for a specified amount of time 
(from the delay parameter to the post), and a client with 2 threads that post 
to those URLs and keep track of when things start and end:

delay_servlet.rb:
require 'webrick'
require 'time'

class DelayServlet < WEBrick::HTTPServlet::AbstractServlet
  def do_POST(request, response)
    start_time = Time.now
    delay = 0
    if request.query["delay"]
      delay = request.query["delay"].to_i
    end

    sleep(delay)

    end_time = Time.now
    response.body = "delayed for #{delay}s, started at " +
      "#{start_time.iso8601}, ended at #{end_time.iso8601}\n"
  end
end

if __FILE__ == $0
  server = WEBrick::HTTPServer.new(:Port => 8000)
  server.mount("/", DelayServlet)

  trap("INT") {server.shutdown}
  server.start
end


delay_client.rb:
require 'net/http'
require 'time'

if __FILE__ == $0
  puts "Main thread start at #{Time.now.iso8601}"

  t1 = Thread.new do
    puts "Thread 1 start at #{Time.now.iso8601}"
    res = Net::HTTP.post_form(URI.parse('http://localhost:8000/'),
                              {'delay'=>'5'})
    puts "Response: " + res.body
    puts "Thread 1 end at #{Time.now.iso8601}"
  end

  t2 = Thread.new do
    puts "Thread 2 start at #{Time.now.iso8601}"
    res = Net::HTTP.post_form(URI.parse('http://localhost:8000/'),
                              {'delay'=>'7'})
    puts "Response: " + res.body
    puts "Thread 2 end at #{Time.now.iso8601}"
  end

  t1.join
  t2.join
  puts "Main thread end at #{Time.now.iso8601}"
end

Output:
Main thread start at 2009-09-10T16:46:17-04:00
Thread 1 start at 2009-09-10T16:46:17-04:00
Thread 2 start at 2009-09-10T16:46:17-04:00
Response: delayed for 5s, started at 2009-09-10T16:46:17-04:00, ended at 
2009-09-10T16:46:22-04:00
Thread 1 end at 2009-09-10T16:46:22-04:00
Response: delayed for 7s, started at 2009-09-10T16:46:17-04:00, ended at 
2009-09-10T16:46:24-04:00
Thread 2 end at 2009-09-10T16:46:24-04:00
Main thread end at 2009-09-10T16:46:24-04:00

So it sure looks like it isn't blocking all threads when waiting for a HTTP 
response.

Ben