@Override
public void operationFinished(Object ctx, final Version version) {
Callback<Void> cb2 = new Callback<Void>() {
@Override
public void operationFailed(final Object ctx, final PubSubException exception) {
logger.error("subscription for subscriber " + subscriberId.toStringUtf8() + " to topic "
+ topic.toStringUtf8() + " failed due to failed listener callback", exception);
// should remove subscription when synchronized cross-region subscription failed
deleteSubscriptionData(topic, subscriberId, version, new Callback<Void>() {
@Override
public void operationFinished(Object context,