Async::Reactor#run_once time

[tleish]

In testing moving a Goliath/EventMachine app to Falcon/Async, we found that request using async-http was a bit slower. In profiling async-http, I noticed 89% of the time was taken in Async::Reactor#run_once. It's not clear to me if this is just waiting for the HTTP response or if something else is going on. If waiting for response, the response from httpbin.org averages 62ms, where Async::Reactor#run_once takes approximately 260ms.

ruby 2.7
async-http 0.60.2
async 1.31.0

require 'async'
require 'async/http/internet'
require 'ruby-prof-flamegraph'

def ruby_prof_wrapper
  RubyProf.start

  results = yield

  result = RubyProf.stop
  printer = RubyProf::FlameGraphPrinter.new(result)

  dir = File.dirname(__FILE__)
  file = File.join(dir, "profile-#{Time.now.to_i}.data")
  File.open(file, 'w') {|file| printer.print(file)}
  results
end

data = {'life' => 42}

Async do
  internet = nil
  ruby_prof_wrapper do
    # Make a new internet:
    internet = Async::HTTP::Internet.new
  
    # Prepare the request:
    headers = [['accept', 'application/json']]
    body = [JSON.dump(data)]
  
    # Issues a POST request:
    response = internet.post("https://httpbin.org/anything", headers, body)
  
    # Save the response body to a local file:
    pp JSON.parse(response.read)
  end
ensure
  # The internet is closed for business:
  internet.close
end

[Samuel Williams]

Thanks, I'll take a look. I don't think we expect to see a significant difference, so there may be a performance regression. The sample code is useful.

[tleish]

FYI, if you right-click and download the SVG from github to your local machine, you can then open the interactive flamgraph in your browser to see better details.