Ruby の net/http のコードを少し読む

require 'net/http'

uri = URI.parse("http:example/image.jpg")
response = Net::HTTP.get_response(uri)

response.code
response.body

これで画像がダウンロードできるわけだが、ライブラリを探る。
　

解読

/home/tomoki/.rbenv/versions/3.1.1/lib/ruby/3.1.0/net/http.rb

module Net
  class HTTP < Protocol
    def HTTP.get_response(uri_or_host, path_or_headers = nil, port = nil, &block)
      if path_or_headers && !path_or_headers.is_a?(Hash)
        host = uri_or_host
        path = path_or_headers
        new(host, port || HTTP.default_port).start {|http|
          return http.request_get(path, &block)
        }
      else
        uri = uri_or_host
        headers = path_or_headers
        start(uri.hostname, uri.port,
              :use_ssl => uri.scheme == 'https') {|http|
          return http.request_get(uri, headers, &block)
        }
      end
    end
  end
end

これの

start(uri.hostname, uri.port,:use_ssl => uri.scheme == 'https') {|http|
  return http.request_get(uri, headers, &block)
}

この部分が呼ばれる。HTTP.startメソッドはどこか。

同じファイルの 608行目からある。

module Net
  class HTTP < Protocol
    def HTTP.start(address, *arg, &block) # :yield: +http+
      arg.pop if opt = Hash.try_convert(arg[-1])
      port, p_addr, p_port, p_user, p_pass = *arg
      p_addr = :ENV if arg.size < 2
      port = https_default_port if !port && opt && opt[:use_ssl]
      http = new(address, port, p_addr, p_port, p_user, p_pass)
      http.ipaddr = opt[:ipaddr] if opt && opt[:ipaddr]

      if opt
        if opt[:use_ssl]
          opt = {verify_mode: OpenSSL::SSL::VERIFY_PEER}.update(opt)
        end
        http.methods.grep(/\A(\w+)=\z/) do |meth|
          key = $1.to_sym
          opt.key?(key) or next
          http.__send__(meth, opt[key])
        end
      end

      http.start(&block)
    end
  end
end

ここの

http = new(address, port, p_addr, p_port, p_user, p_pass)

が重要そうだ。http = Http.newはどこにあるのか？ 682行にある。最後でhttp.start(&block)が呼ばれている。どこにあるのか？

961行目にある。

module Net
  class HTTP < Protocol
    def start  # :yield: http
      raise IOError, 'HTTP session already opened' if @started
      if block_given?
        begin
          do_start
          return yield(self)
        ensure
          do_finish
        end
      end
      do_start
      self
    end

    def do_start
      connect
      @started = true
    end
    private :do_start

    def connect
      if use_ssl?
        # reference early to load OpenSSL before connecting,
        # as OpenSSL may take time to load.
        @ssl_context = OpenSSL::SSL::SSLContext.new
      end

      if proxy? then
        conn_addr = proxy_address
        conn_port = proxy_port
      else
        conn_addr = conn_address
        conn_port = port
      end

      D "opening connection to #{conn_addr}:#{conn_port}..."
      begin
        s = Socket.tcp conn_addr, conn_port, @local_host, @local_port, connect_timeout: @open_timeout
      rescue => e
        e = Net::OpenTimeout.new(e) if e.is_a?(Errno::ETIMEDOUT) #for compatibility with previous versions
        raise e, "Failed to open TCP connection to " +
          "#{conn_addr}:#{conn_port} (#{e.message})"
      end
      s.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
      D "opened"
      if use_ssl?
        if proxy?
          plain_sock = BufferedIO.new(s, read_timeout: @read_timeout,
                                      write_timeout: @write_timeout,
                                      continue_timeout: @continue_timeout,
                                      debug_output: @debug_output)
          buf = "CONNECT #{conn_address}:#{@port} HTTP/#{HTTPVersion}\r\n"
          buf << "Host: #{@address}:#{@port}\r\n"
          if proxy_user
            credential = ["#{proxy_user}:#{proxy_pass}"].pack('m0')
            buf << "Proxy-Authorization: Basic #{credential}\r\n"
          end
          buf << "\r\n"
          plain_sock.write(buf)
          HTTPResponse.read_new(plain_sock).value
          # assuming nothing left in buffers after successful CONNECT response
        end

        ssl_parameters = Hash.new
        iv_list = instance_variables
        SSL_IVNAMES.each_with_index do |ivname, i|
          if iv_list.include?(ivname)
            value = instance_variable_get(ivname)
            unless value.nil?
              ssl_parameters[SSL_ATTRIBUTES[i]] = value
            end
          end
        end
        @ssl_context.set_params(ssl_parameters)
        @ssl_context.session_cache_mode =
          OpenSSL::SSL::SSLContext::SESSION_CACHE_CLIENT |
          OpenSSL::SSL::SSLContext::SESSION_CACHE_NO_INTERNAL_STORE
        @ssl_context.session_new_cb = proc {|sock, sess| @ssl_session = sess }
        D "starting SSL for #{conn_addr}:#{conn_port}..."
        s = OpenSSL::SSL::SSLSocket.new(s, @ssl_context)
        s.sync_close = true
        # Server Name Indication (SNI) RFC 3546
        s.hostname = @address if s.respond_to? :hostname=
        if @ssl_session and
           Process.clock_gettime(Process::CLOCK_REALTIME) < @ssl_session.time.to_f + @ssl_session.timeout
          s.session = @ssl_session
        end
        ssl_socket_connect(s, @open_timeout)
        if (@ssl_context.verify_mode != OpenSSL::SSL::VERIFY_NONE) && @ssl_context.verify_hostname
          s.post_connection_check(@address)
        end
        D "SSL established, protocol: #{s.ssl_version}, cipher: #{s.cipher[0]}"
      end
      @socket = BufferedIO.new(s, read_timeout: @read_timeout,
                               write_timeout: @write_timeout,
                               continue_timeout: @continue_timeout,
                               debug_output: @debug_output)
      @last_communicated = nil
      on_connect
    rescue => exception
      if s
        D "Conn close because of connect error #{exception}"
        s.close
      end
      raise
    end
    private :connect
  end
end

Http#connectが重要そうだ。

s = Socket.tcp conn_addr, conn_port, @local_host, @local_port, connect_timeout: @open_timeout

でs = Socket.tcpを呼んでいる。

Socket.tcpメソッドのマニュアルはここにある。ブロック付きだと

require 'socket'

Socket.tcp("www.ruby-lang.org", 80) {|sock|
  sock.print "GET / HTTP/1.0\r\nHost: www.ruby-lang.org\r\n\r\n"
  sock.close_write
  puts sock.read
}

のように使うらしい。

つまり、s = Socket.tcpには TCP/IP で host に接続するソケットオブジェクトが入る、と。

続き。

s.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)    #1004行
#1054行
@socket = BufferedIO.new(s, read_timeout: @read_timeout,
                         write_timeout: @write_timeout,
                         continue_timeout: @continue_timeout,
                         debug_output: @debug_output)
on_connect    #1059行

いろいろある。Net::BufferedIOは /home/tomoki/.rbenv/versions/3.1.1/lib/ruby/3.1.0/net/protocol.rb の 115行からある。まあ、結局sが io として@socketに入る。

解読2

もとに戻る。Http#request_getはどこにあるか。1439行にある。

def request_get(path, initheader = nil, &block) # :yield: +response+
  request(Get.new(path, initheader), &block)
end

#1528行
def request(req, body = nil, &block)  # :yield: +response+
  unless started?
    start {
      req['connection'] ||= 'close'
      return request(req, body, &block)
    }
  end
  if proxy_user()
    req.proxy_basic_auth proxy_user(), proxy_pass() unless use_ssl?
  end
  req.set_body_internal body
  res = transport_request(req, &block)
  if sspi_auth?(res)
    sspi_auth(req)
    res = transport_request(req, &block)
  end
  res
end

Net::Http::Getはどこにあるか。

/home/tomoki/.rbenv/versions/3.1.1/lib/ruby/3.1.0/net/http/requests.rb にある。

class Net::HTTP::Get < Net::HTTPRequest
  METHOD = 'GET'
  REQUEST_HAS_BODY  = false
  RESPONSE_HAS_BODY = true
end

Net::HTTPRequestは /home/tomoki/.rbenv/versions/3.1.1/lib/ruby/3.1.0/net/http/requests.rb にある。

class Net::HTTPRequest < Net::HTTPGenericRequest
end

　
じつは本体は、/home/tomoki/.rbenv/versions/3.1.1/lib/ruby/3.1.0/net/http/generic_request.rb にある。

class Net::HTTPGenericRequest

  include Net::HTTPHeader

  def initialize(m, reqbody, resbody, uri_or_path, initheader = nil)
    @method = m
    @request_has_body = reqbody
    @response_has_body = resbody

    if URI === uri_or_path then
      raise ArgumentError, "not an HTTP URI" unless URI::HTTP === uri_or_path
      raise ArgumentError, "no host component for URI" unless uri_or_path.hostname
      @uri = uri_or_path.dup
      host = @uri.hostname.dup
      host << ":".freeze << @uri.port.to_s if @uri.port != @uri.default_port
      @path = uri_or_path.request_uri
      raise ArgumentError, "no HTTP request path given" unless @path
    else
      @uri = nil
      host = nil
      raise ArgumentError, "no HTTP request path given" unless uri_or_path
      raise ArgumentError, "HTTP request path is empty" if uri_or_path.empty?
      @path = uri_or_path.dup
    end

    @decode_content = false

    if Net::HTTP::HAVE_ZLIB then
      if !initheader ||
         !initheader.keys.any? { |k|
           %w[accept-encoding range].include? k.downcase
         } then
        @decode_content = true if @response_has_body
        initheader = initheader ? initheader.dup : {}
        initheader["accept-encoding"] =
          "gzip;q=1.0,deflate;q=0.6,identity;q=0.3"
      end
    end

    initialize_http_header initheader
    self['Accept'] ||= '*/*'
    self['User-Agent'] ||= 'Ruby'
    self['Host'] ||= host if host
    @body = nil
    @body_stream = nil
    @body_data = nil
  end
end

　
もう一度戻る。再掲載。

#1528行
def request(req, body = nil, &block)  # :yield: +response+
  unless started?
    start {
      req['connection'] ||= 'close'
      return request(req, body, &block)
    }
  end
  if proxy_user()
    req.proxy_basic_auth proxy_user(), proxy_pass() unless use_ssl?
  end
  req.set_body_internal body
  res = transport_request(req, &block)
  if sspi_auth?(res)
    sspi_auth(req)
    res = transport_request(req, &block)
  end
  res
end

問題はこれかな。

res = transport_request(req, &block)

reqはNet::Http::Get.newが入っている。では、transport_requestメソッドは何でどこか。

1562行目である。

module Net
  class HTTP < Protocol
    def transport_request(req)
      count = 0
      begin
        begin_transport req
        res = catch(:response) {
          begin
            req.exec @socket, @curr_http_version, edit_path(req.path)
          rescue Errno::EPIPE
            # Failure when writing full request, but we can probably
            # still read the received response.
          end

          begin
            res = HTTPResponse.read_new(@socket)
            res.decode_content = req.decode_content
          end while res.kind_of?(HTTPInformation)

          res.uri = req.uri

          res
        }
        res.reading_body(@socket, req.response_body_permitted?) {
          yield res if block_given?
        }
      rescue Net::OpenTimeout
        raise
      rescue Net::ReadTimeout, IOError, EOFError,
             Errno::ECONNRESET, Errno::ECONNABORTED, Errno::EPIPE, Errno::ETIMEDOUT,
             # avoid a dependency on OpenSSL
             defined?(OpenSSL::SSL) ? OpenSSL::SSL::SSLError : IOError,
             Timeout::Error => exception
        if count < max_retries && IDEMPOTENT_METHODS_.include?(req.method)
          count += 1
          @socket.close if @socket
          D "Conn close because of error #{exception}, and retry"
          retry
        end
        D "Conn close because of error #{exception}"
        @socket.close if @socket
        raise
      end

      end_transport req, res
      res
    rescue => exception
      D "Conn close because of error #{exception}"
      @socket.close if @socket
      raise exception
    end
  end
end

res = HTTPResponse.read_new(@socket)だ。
　

解読3