@Override
    public void preCreateTable(ObserverContext<MasterCoprocessorEnvironment> ctx,
      TableDescriptor desc, RegionInfo[] regions) throws IOException {
      // we rely on the fact that there is only 1 instance of our MasterObserver
      this.start = EnvironmentEdgeManager.currentTime();
    }
MasterObserver that has a Timer metric for create table operation.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorMetrics.java