@Override
    public void postCreateTable(ObserverContext<MasterCoprocessorEnvironment> ctx,
      TableDescriptor desc, RegionInfo[] regions) throws IOException {
      if (this.start > 0) {
        long time = EnvironmentEdgeManager.currentTime() - start;
        LOG.info("Create table took: " + time);
        createTableTimer.updateMillis(time);
      }
    }
MasterObserver that has a Timer metric for create table operation.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorMetrics.java