@Override
    public void postRollWALWriterRequest(ObserverContext<RegionServerCoprocessorEnvironment> ctx)
      throws IOException {
      // Increment the Counter whenever the coprocessor is called
      rollWALCounter.increment();
    }
This is the Counter metric object to keep track of the current count across invocations
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestCoprocessorMetrics.java