Instrument HTTP calls made with Net::HTTP

net_instrumentation.rb

HTTP_LOG_PATH = File.expand_path("~/http.log")
FileUtils.rm_f(HTTP_LOG_PATH)

module NetInstrumentation
  def self.included(base)
    puts "Writing HTTP out to ~/http.log"
    base.send(:alias_method, :__original_request, :request)
    base.send(:alias_method, :request, :__logged_request)
  end

  def __logged_request(*args, &block)
    request = args.first
    request_data = JSON.parse(request.to_json)
    request_data[:uri] = request.uri
    request_data[:path] = request.path
    request_data[:body] = request.body
    return __original_request(*args, &block).tap do |response|
      response_data = JSON.parse(response.to_json)
      response_data[:code] = response.code
      response_data[:message] = response.message
      response_data[:body] = response.body
      data = {request: request_data, response: response_data}.to_json
      __logger.info(data)
    end
  end

  def __logger
    @__logger ||= Logger.new(HTTP_LOG_PATH)
  end
end


Net::HTTP.send(:include, NetInstrumentation)

def http_log
  File.readlines(HTTP_LOG_PATH).map do |line|
    JSON.parse(line) rescue nil
  end.compact
end

If you load 'net_instrumentation.rb' from a console, any HTTP calls made with Net::HTTP will be logged to ~/http.log. Each call is represented by a blob of JSON, 1 per line. The JSON object contains a request and response attribute with appropriate data.

There is also an http_log method in the global namespace available in the console. You can invoke it to get an array of the call blobs as hashes. This will allow you to do things like

http_log.select{|call| call[:response][:code] != 200}

and otherwise easily introspect the contents of the log.

This is a very hacky way to be able to see details of HTTP (API) calls going out from a Ruby app from a console. The basic use would be...

> bundle exec rails console
2.1.2 :001 > load File.expand_path("~/net_instrumentation.rb")
Writing HTTP out to ~/http.log
 => true

The invoke your code that would result in the HTTP calls going out and then interact with the http log entries...

2.1.2 :002 > http_log.first['response']['code']
 => "200"

Line 17 wants to make my eyes bleed. return magic.tap do |wtf| hahaha

@randito I'll have you know my shitty code saved 1000 puppy lives today, lol!