@Override
 public void removeActiveLedger(long ledgerId) {
   activeLedgers.remove(ledgerId);
 }
 @Override
 public boolean containsActiveLedger(long ledgerId) {
   return activeLedgers.containsKey(ledgerId);
 }
 @Override
 public void addActiveLedger(long ledgerId, boolean active) {
   activeLedgers.put(ledgerId, active);
 }