@Override
  public void onHardDown() {
    logger.trace("Marking resource {} as Hard down", resource);
    hardDown.set(true);
  }
Called when it is known externally that the resource has gone down. An immediate call to {@link #isDown()} will
return true.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/FixedBackoffResourceStatePolicy.java