Combine a rack app with reel, to get the best of both worlds: A rack app (could be sinatra or even rails) for routing and dealing with pure HTTP requests, and all the power of reel and celluloid for dealing with things like websockets.

mounted_server.rb

# Copyright (c) 2013 Jonathan Stott
# 
# Permission  is  hereby granted, free of charge, to any person ob-
# taining a copy of  this  software  and  associated  documentation
# files  (the "Software"), to deal in the Software without restric-
# tion, including without limitation the rights to use, copy, modi-
# fy, merge, publish, distribute, sublicense, and/or sell copies of
# the Software, and to permit persons to whom the Software is  fur-
# nished to do so, subject to the following conditions:
# 
# The  above  copyright  notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF  ANY  KIND,
# EXPRESS  OR  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE  AND  NONIN-
# FRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER  IN  AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN  THE
# SOFTWARE.
require 'reel'
require 'rack/body_proxy'

# hacky fix to make this work
module Rack
  class BodyProxy
    include Enumerable
  end
end

module Reel
  class MountedServer < Server
    attr_reader :rack
    def initialize(rack, host, port)
      super(host, port, &method(:on_connection))
      @rack = rack
    end

    def on_connection(connection)
      while request = connection.request
        case request
        when Request
          route_request connection, request
        when WebSocket
          route_websocket request
        end
      end
    end

    def route_request(connection, request)
      opts = {:method => request.method, :input => request.body, "REMOTE_ADDR" => connection.remote_addr}
      opts.merge!(convert_headers(request.headers))

      status, headers, body = rack.call Rack::MockRequest.env_for(request.url, opts)

      # This is currently not that as body is almost certainly a String or BodyProxy.
      # Maybe I need to unwrap?
      response_klass = body.is_a?(Stream) ? StreamResponse : Response

      connection.respond(response_klass.new(status_symbol(status), headers, body))

      # I hope this won't blow up
      body.close if body.respond_to?(:close)
    end

    def convert_headers(headers)
      Hash[headers.map { |key, value| ['HTTP_' + key.upcase.gsub('-','_'),value ] }]
    end

    def route_websocket(socket)
    end

    def status_symbol(status)
      status.is_a?(Fixnum) ? Http::Response::STATUS_CODES[status].downcase.gsub(/\s|-/, '_').to_sym : status.to_sym
    end


    # The code in CommonLogger is copied almost verbatim from rack/common_logger which is made available
    # under the following terms:
    # Copyright (c) 2007, 2008, 2009, 2010, 2011, 2012 Christian Neukirchen <purl.org/net/chneukirchen>
    # 
    # Permission is hereby granted, free of charge, to any person obtaining a copy
    # of this software and associated documentation files (the "Software"), to
    # deal in the Software without restriction, including without limitation the
    # rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
    # sell copies of the Software, and to permit persons to whom the Software is
    # furnished to do so, subject to the following conditions:
    # 
    # The above copyright notice and this permission notice shall be included in
    # all copies or substantial portions of the Software.
    # 
    # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
    # THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER 
    # IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
    # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    # Rack::CommonLogger forwards every request to the given +app+, and
    # logs a line in the
    # {Apache common log format}[http://httpd.apache.org/docs/1.3/logs.html#common]
    # to the +logger+.
    #
    # If +logger+ is nil, CommonLogger will fall back +rack.errors+, which is
    # an instance of Rack::NullLogger.
    #
    # +logger+ can be any class, including the standard library Logger, and is
    # expected to have a +write+ method, which accepts the CommonLogger::FORMAT.
    # According to the SPEC, the error stream must also respond to +puts+
    # (which takes a single argument that responds to +to_s+), and +flush+
    # (which is called without arguments in order to make the error appear for
    # sure)
    class CommonLogger
      # Common Log Format: http://httpd.apache.org/docs/1.3/logs.html#common
      #
      #   lilith.local - - [07/Aug/2006 23:58:02] "GET / HTTP/1.1" 500 -
      #
      #   %{%s - %s [%s] "%s %s%s %s" %d %s\n} %
      FORMAT = %{%s - %s [%s] "%s %s%s %s" %d %s %0.4f}

      def initialize(app, logger=nil)
        @app = app
        @logger = logger
      end

      def call(env)
        began_at = Time.now
        status, header, body = @app.call(env)
        header = Rack::Utils::HeaderHash.new(header)
        body = Rack::BodyProxy.new(body) { log(env, status, header, began_at) }
        [status, header, body]
      end

      private

      def log(env, status, header, began_at)
        now = Time.now
        length = extract_content_length(header)

        logger = @logger || Celluloid.logger
        logger.info FORMAT % [
          env['HTTP_X_FORWARDED_FOR'] || env["REMOTE_ADDR"] || "-",
          env["REMOTE_USER"] || "-",
          now.strftime("%d/%b/%Y %H:%M:%S"),
          env["REQUEST_METHOD"],
          env["PATH_INFO"],
          env["QUERY_STRING"].empty? ? "" : "?"+env["QUERY_STRING"],
          env["HTTP_VERSION"],
          status.to_s[0..3],
          length,
          now - began_at ]
      end

      def extract_content_length(headers)
        value = headers['Content-Length'] or return '-'
        value.to_s == '0' ? '-' : value
      end
    end
  end
end

mounted_server_example.rb

require 'mounted_server'

class Server < Reel::MountedServer
  include Celluloid::Logger
  def initialize(rack, host = "127.0.0.1", port = 1234)
    super(rack, host, port)
  end

  def route_websocket(socket)
    info "#{request.peeraddr[2]} connected"
    if socket.url == "/chat"
      Client.new(socket)
    else
      info "Invalid WebSocket request for: #{socket.url}"
      socket.close
    end
  end
end

require 'sinatra'
class Test < Sinatra::Application
  disable :logging
  use Reel::MountedServer::CommonLogger
  get '/' do
    p request.user_agent
    p url
    'hi!'
  end
end

Server.supervise_as :server, Test.new
sleep