public List<GroupTracker> getGroupTrackers() {
    List<GroupTracker> groupTrackers = new ArrayList<>(getActiveGroupTrackers());
    groupTrackers.add(getStandByGroupTracker());
    return groupTrackers;
  }
@return getting maximum group id for this data node
ambry-replication/src/main/java/com/github/ambry/replication/continuous/DataNodeTracker.java