Method call

src/scheduler/scheduler.cpp:254–295

  }

  Future<APIResult> call(const Call& callMessage)
  {
    Option<Error> error =
      validation::scheduler::call::validate(devolve(callMessage));

    if (error.isSome()) {
      return Failure(error->message);
    }

    if (callMessage.type() == Call::SUBSCRIBE) {
      return Failure("This method doesn't support SUBSCRIBE calls");
    }

    if (state != SUBSCRIBED) {
      return Failure(
          "Cannot perform calls until subscribed. Current state: " +
          stringify(state));
    }

    VLOG(1) << "Sending " << callMessage.type() << " call to " << master.get();

    // TODO(vinod): Add support for sending MESSAGE calls directly
    // to the slave, instead of relaying it through the master, as
    // the scheduler driver does.

    process::http::Request request;
    request.method = "POST";
    request.url = master.get();
    request.body = serialize(contentType, callMessage);
    request.keepAlive = true;
    request.headers = {{"Accept", stringify(contentType)},
                       {"Content-Type", stringify(contentType)}};

    // TODO(tillt): Add support for multi-step authentication protocols.
    return authenticatee->authenticate(request, credential)
      .recover([](const Future<process::http::Request>& future) {
        return Failure(
            stringify("HTTP authenticatee ") +
            (future.isFailed() ? "failed: " + future.failure() : "discarded"));
      })
      .then(defer(self(), &Self::_call, callMessage, lambda::_1));
  }

  void reconnect()
  {