Async rack app to fetch giphy gifs

config.ru

app = lambda { |env|
  request = Rack::Request.new(env)

  type  = request.GET["list"] || "search"
  query = request.GET["q"] || "cats"

  giphy_request = GiphyRequest.new(type, query)

  giphy_request.callback do
    headers = {
      "Content-Type"                     => "application/json",
      "Access-Control-Allow-Credentials" => "true",
      "Access-Control-Allow-Methods"     => "GET, POST, OPTIONS",
      "Access-Control-Allow-Origin"      => "*"
    }

    body = {
      query:   type,
      results: giphy_request.results
    }.to_json

    env['async.callback'].call [200, headers, body]
  end

  throw :async
}

run app

Gemfile

source "https://rubygems.org"

gem "em-http-request"
gem "eventmachine"
gem "json"
gem "rack"
gem "thin"

giphy_request.rb

require "eventmachine"
require "em-http-request"
require "json"

class GiphyRequest
  include EM::Deferrable

  attr_reader :results

  def initialize(type, query = "")
    @results = []

    http_query = { api_key: "XXXXXXXXXXXX" }

    if type == "search"
      http_query[:q] = query
    end

    req = EM::HttpRequest.new("http://api.giphy.com").get(
      path: "/v1/gifs/#{type}",
      query: http_query
    )

    req.callback do
      populate_results(req.response, type)
      succeed
    end
  end

  private
  def populate_results(response, type)
    if type == "random"
      @results.push(
        url: JSON.parse(response)["data"]["image_original_url"]
      )
    else
      JSON.parse(response)["data"].each do |gif|
        @results.push(
          url:       gif["images"]["original"]["url"],
          staticUrl: gif["images"]["fixed_width_still"]["url"]
        )
      end
    end
  end
end

Nice, I've never seen throw :async before, but with a bit of searching found this article. Interesting to see they ended up with a Sinatra-Async solution in the end too which reads quite nicely. I'll discuss this with the team on Thursday to see which direction we could take.

BTW. Having read the article above, it seems we could in theory run this type of evented script within a Rails stack. Do you think there is any way we could use the current application servers to service these evented requests still? It would make life a lot easier if we didn't need to provision a new type of server specifically to service these requests.