Method attachContainerOutput

src/slave/containerizer/mesos/io/switchboard.cpp:1803–1850

Future<http::Response> IOSwitchboardServerProcess::attachContainerOutput(
    ContentType acceptType,
    Option<ContentType> messageAcceptType)
{
  http::Pipe pipe;
  http::OK ok;

  ok.headers["Content-Type"] = stringify(acceptType);

  // If a client sets the 'Accept' header expecting a streaming response,
  // `messageAcceptType` would always be set and we use it as the value of
  // 'Message-Content-Type' response header.
  ContentType messageContentType = acceptType;
  if (streamingMediaType(acceptType)) {
    CHECK_SOME(messageAcceptType);
    ok.headers[MESSAGE_CONTENT_TYPE] = stringify(messageAcceptType.get());
    messageContentType = messageAcceptType.get();
  }

  ok.type = http::Response::PIPE;
  ok.reader = pipe.reader();

  // We store the connection in a list and wait for asynchronous
  // calls to `receiveOutput()` to actually push data out over the
  // connection. If we ever detect a connection has been closed,
  // we remove it from this list.
  HttpConnection connection(pipe.writer(), messageContentType);
  auto iterator = outputConnections.insert(outputConnections.end(), connection);

  // We use the `startRedirect` promise to indicate when we should
  // begin reading data from our `stdoutFromFd` and `stderrFromFd`
  // file descriptors. If we were started with the `waitForConnection`
  // parameter set to `true`, only set this promise here once the
  // first connection has been established.
  if (!startRedirect.future().isReady()) {
    startRedirect.set(Nothing());
  }

  connection.closed()
    .then(defer(self(), [this, iterator]() {
      // Erasing from a `std::list` only invalidates the iterator of
      // the object being erased. All other iterators remain valid.
      outputConnections.erase(iterator);
      return Nothing();
    }));

  return ok;
}


void IOSwitchboardServerProcess::outputHook(