public long setAgeOfLastAppliedOp(long timestamp) {
    long age = 0;
    if (lastTimestampForAge != timestamp) {
      lastTimestampForAge = timestamp;
      age = EnvironmentEdgeManager.currentTime() - lastTimestampForAge;
    }
    mss.setLastAppliedOpAge(age);
    return age;
  }
Set the age of the last applied operation
@param timestamp The timestamp of the last operation applied.
@return the age that was set
hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/MetricsSink.java