Method _attachContainerOutput

src/slave/http.cpp:4350–4451

Future<Response> Http::_attachContainerOutput(
    const mesos::agent::Call& call,
    const RequestMediaTypes& mediaTypes) const
{
  const ContainerID& containerId =
    call.attach_container_output().container_id();

  return slave->containerizer->attach(containerId)
    .then([call, mediaTypes](Connection connection)
        -> Future<Response> {
      Request request;
      request.method = "POST";
      request.headers = {{"Accept", stringify(mediaTypes.accept)},
                         {"Content-Type", stringify(mediaTypes.content)}};

      // If a client sets the 'Accept' header expecting a streaming response,
      // `messageAccept` would always be set and we use it as the value of
      // 'Message-Accept' header.
      if (streamingMediaType(mediaTypes.accept)) {
        CHECK_SOME(mediaTypes.messageAccept);
        request.headers[MESSAGE_ACCEPT] =
          stringify(mediaTypes.messageAccept.get());
      }

      // The 'HOST' header must be EMPTY for non Internet addresses.
      // TODO(vinod): Instead of setting domain to empty string (which results
      // in an empty HOST header), add a new URL constructor that doesn't
      // require domain or IP.
      request.url.domain = "";

      // NOTE: The path is currently ignored by the switch board.
      request.url.path = "/";

      request.type = Request::BODY;
      request.body = serialize(mediaTypes.content, call);

      // We capture `connection` here to ensure that it doesn't go
      // out of scope until the `onAny` handler on `transform` is executed.
      return connection.send(request, true)
        .then([connection, mediaTypes](const Response& response)
            -> Future<Response> {
          if (response.status != OK().status) {
            return response;
          }

          // Evolve the `ProcessIO` records in the Response body to v1
          // before sending them to the client.
          Pipe pipe;
          Pipe::Writer writer = pipe.writer();

          OK ok;
          ok.headers = response.headers; // Reuse headers from response.

          // If a client sets the 'Accept' header expecting a streaming
          // response, `messageAccept` would always be set and we use it
          // to deserialize/evolve messages in the streaming response.
          ContentType messageContentType = mediaTypes.accept;
          if (streamingMediaType(mediaTypes.accept)) {