Method save

src/resource_provider/daemon.cpp:431–472

NOTE: We provide atomic (all-or-nothing) semantics here by always writing to a temporary file to the staging directory first then using `os::rename` to atomically move it to the desired path.

// writing to a temporary file to the staging directory first then using
// `os::rename` to atomically move it to the desired path.
Try<Nothing> LocalResourceProviderDaemonProcess::save(
    const string& path,
    const ResourceProviderInfo& info)
{
  CHECK_SOME(configDir);

  // NOTE: We create the staging directory in the resource provider
  // config directory to make sure that the renaming below does not
  // cross devices (MESOS-2319).
  // TODO(chhsiao): Consider adding a way to garbage collect the staging
  // directory.
  const string stagingDir = path::join(configDir.get(), STAGING_DIR);
  Try<Nothing> mkdir = os::mkdir(stagingDir);
  if (mkdir.isError()) {
    return Error(
        "Failed to create directory '" + stagingDir + "': " + mkdir.error());
  }

  const string stagingPath = path::join(stagingDir, Path(path).basename());

  Try<Nothing> write = os::write(stagingPath, stringify(JSON::protobuf(info)));
  if (write.isError()) {
    // Try to remove the temporary file on error.
    os::rm(stagingPath);

    return Error(
        "Failed to write temporary file '" + stagingPath + "': " +
        write.error());
  }

  Try<Nothing> rename = os::rename(stagingPath, path);
  if (rename.isError()) {
    // Try to remove the temporary file on error.
    os::rm(stagingPath);

    return Error(
        "Failed to rename '" + stagingPath + "' to '" + path + "': " +
        rename.error());
  }

  return Nothing();
}


Future<Nothing> LocalResourceProviderDaemonProcess::launch(