long getOldestWalAge() {
    long now = EnvironmentEdgeManager.currentTime();
    long timestamp = getOldestWalTimestamp();
    if (timestamp == Long.MAX_VALUE) {
      // If there are no wals in the queue then set the oldest wal timestamp to current time
      // so that the oldest wal age will be 0.
      timestamp = now;
    }
    long age = now - timestamp;
    return age;
  }
Remove all the elements from the queue corresponding to walGroupId
@param walGroupId walGroupId
hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationSourceLogQueue.java