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