Is it possible to initiate multiple parallel http requests using EventMachine with Ruby 1.8

em-synchrony.rb implements this feature with Fibers but I would go for a non-Fibre version with 1.8 MRI.

EM.run do开发者_StackOverflow中文版
  http = EM::Protocols::HttpClient2.connect("www.google.com", 80)
  request = http.get("/")
  request.callback do
    puts request.status
    EM.stop
  end
end

Have a look at em-http-request:

EM.run do
  http1 = EventMachine::HttpRequest.new('http://example.com/1').get
  http1.callback do
    p http1.response
  end
  http2 = EventMachine::HttpRequest.new('http://example.com/2').get
  http2.callback do
    p http2.response
  end
end

If you can look outside of EventMachine, Typhoeus is an easy to use HTTP client that comes with Hydra, which gives the ability to process multiple requests in parallel.

I used it for a couple things and it's easy to set up. This is some untested code torn out of something I wrote the other day:

require 'typhoeus'

hydra = Typhoeus::Hydra.new(:max_concurrency => 10)
urls.each do |url|
  request = Typhoeus::Request.new(url)

  request.on_complete do |resp|
    filename = resp.request.url.split('/').last
    puts "writing #{filename}"
    File.open(filename, 'w') do |fo|
      fo.write resp.body
    end  
  end
  puts "queuing #{ url }"
  hydra.queue(request)
end

hydra.run