How many thread?!

ruby-talk
1

Hi list,

I've a question about threads counting... :slight_smile:

···

------------------------------------------------------------------
#!/usr/bin/ruby

require 'timeout'

timeout = 2
server = %w(127.0.0.1 127.0.0.2 127.0.0.3 127.0.0.4)

def check (host,timeout)
puts "checking... #{host}"
timeout(timeout) do
  begin
   `/usr/bin/nslookup www.test.org #{host}`
  rescue Timeout::Error
  end
end
end

threads = []

server.each { |host|
puts Thread.list.size
threads << Thread.new(host) { |host|
  check(host,timeout)
}
}

threads.each {|th| th.join }
------------------------------------------------------------------

It will produces:

1
checking... 127.0.0.1
3
checking... 127.0.0.2
5
checking... 127.0.0.3
7
checking... 127.0.0.4

7 threads for 4 requests?!

Without timeout:

1
checking... 127.0.0.1
2
checking... 127.0.0.2
3
checking... 127.0.0.3
4
checking... 127.0.0.4

4 threads for 4 requests!

Why? Timeout produces a new threads?

Thank you,
Al
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2

Alfonso Caponi wrote:

Why? Timeout produces a new threads?

Yes.

$ less /usr/lib/ruby/1.8/timeout.rb

...

  def timeout(sec, exception=Error)
    return yield if sec == nil or sec.zero?
    raise ThreadError, "timeout within critical session" if
Thread.critical
    begin
      x = Thread.current
      y = Thread.start {
        sleep sec
        x.raise exception, "execution expired" if x.alive?
      }
      yield sec
      # return true
    ensure
      y.kill if y and y.alive?
    end
  end

  module_function :timeout

···

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