Function initialize

src/linux/systemd.cpp:109–195

Try<Nothing> initialize(const Flags& flags)
{
  static Once* initialized = new Once();

  if (initialized->once()) {
    return Nothing();
  }

  if (!systemd::exists()) {
    return Error("systemd does not exist on this system");
  }

  systemd_flags = new Flags(flags);

  // Do not initialize any state if we do not have systemd support enabled.
  if (!systemd_flags->enabled) {
    initialized->done();
    return Nothing();
  }

  // If flags->runtime_directory doesn't exist, then we can't proceed.
  if (!os::exists(CHECK_NOTNULL(systemd_flags)->runtime_directory)) {
    return Error("Failed to locate systemd runtime directory: " +
                 CHECK_NOTNULL(systemd_flags)->runtime_directory);
  }

  // On systemd environments we currently migrate executor pids and processes
  // that need to live alongside the executor into a separate executor slice.
  // This allows the life-time of the process to be extended past the life-time
  // of the slave. See MESOS-3352.
  // This function takes responsibility for creating and starting this slice.
  // We inject a `Subprocess::ParentHook` into the `subprocess` function that
  // migrates pids into this slice if the `EXTEND_LIFETIME` option is set on the
  // `subprocess` call.

  // Ensure that the `MESOS_EXECUTORS_SLICE` exists and is running.
  // TODO(jmlvanre): Prevent racing between multiple agents for this creation
  // logic.

  // Check whether the `MESOS_EXECUTORS_SLICE` already exists. Create it if
  // it does not exist.
  // We explicitly don't modify the file if it exists in case operators want
  // to over-ride the settings for the slice that we provide when we create
  // the `Unit` below.
  const Path path(path::join(
      systemd::runtimeDirectory(),
      mesos::MESOS_EXECUTORS_SLICE));

  if (!systemd::slices::exists(path)) {
    // A simple systemd file to allow us to start a new slice.
    string unit = "[Unit]\nDescription=Mesos Executors Slice\n";

    Try<Nothing> create = systemd::slices::create(path, unit);

    if (create.isError()) {
      return Error("Failed to create systemd slice '" +
                   stringify(mesos::MESOS_EXECUTORS_SLICE) +
                   "': " + create.error());