Rails controller to receive feeds from the Hub of PubSubHubbub.

push_controller.rb

class JmxController < ApplicationController
  DATA_DIR     = "/path/to/jmx/data/"
  VERIFY_TOKEN = "hoge"

  # application_controller 内の
  # "protect_from_forgery with: :exception"
  # を無効にする設定
  # （ワーニングが出力されないようにするため）
  skip_before_filter :verify_authenticity_token

  def index
    req_method = request.request_method

    # HTTP リクエスト別に振り分け
    if req_method == "GET"
      # 各パラメータの取得
      p_mode         = params['hub.mode']
      p_topic        = params['hub.topic']
      p_challenge    = params['hub.challenge']
      p_verify_token = params['hub.verify_token']

      # hub.mode チェック
      if p_mode == "subscribe" || p_mode == "unsubscribe"
        # hub.verify_token チェック
        if p_verify_token == VERIFY_TOKEN
          # Content-type に "text/plain" を指定し、
          # challenge コードをそのまま返却
          response.headers['Content-Type'] = "text/plain"
          render text: p_challenge.chomp, status: 200
        else
          render nothing: true, status: 404
        end
      else
        render nothing: true, status: 404
      end
    elsif req_method == "POST"
      # リクエストボディの取得
      req_body = request.body.read

      # ヘッダ HTTP_X_HUB_SIGNATURE の値を取得
      hub_sig = request.env['HTTP_X_HUB_SIGNATURE']

      # HMAC-SHA1 の計算
      sha1 = OpenSSL::HMAC::hexdigest(OpenSSL::Digest::SHA1.new, VERIFY_TOKEN, req_body)

      logger.info "#### hub_sig = #{hub_sig}"
      logger.info "#### sha1    = #{sha1}"

      # ファイルとして保存
      # ## 実際は、HTTP_X_HUB_SIGNATURE の値と
      # ## と verigy_token から計算した HMAC-SHA1 が等しい場合のみ処理を行う
      file_name = "#{Time.now.strftime("%Y%m%d%H%M%S")}_atom.xml"
      File.open("#{DATA_DIR}#{file_name}", 'wb') { |f| f.write req_body }

      render nothing: true, status: 200
    end
  end
end

Very good! However, I am not sure the VERIFY_TOKEN usage is the one intended by the spec. As a matter of facts it has been deprecated from the 0.4 version of the PubsubHubbub spec.