Use with watchr to reload pages on a remote site periodically to check for changes.

remote_site_watchr.rb

require 'net/http'
require 'mechanize'

class RemoteSiteWatchr
  def initialize(host, urls, &block)
    @host = host
    @urls = urls
    @block = block

    @agent = Mechanize.new
  end

  def start
    prior_hashes = {}

    Thread.new do
      while true
        @urls.each do |uri|
          target = "http://#{@host}#{uri}"
          begin
            page = @agent.get(target)

            hash = Digest::MD5.hexdigest(page.body)

            prior_hashes[uri] = hash if !prior_hashes[uri]
            if prior_hashes[uri] != hash
              prior_hashes[uri] = hash

              puts ">>> #{uri} changed, rerunning..."
              @block.call
              break
            end
          rescue StandardError => e
            puts "[ERROR] #{target}: #{e.message}"
          end
        end

        sleep 5
      end
    end
  end
end