@Override
  public RegionScanner postScannerOpen(
    final ObserverContext<? extends RegionCoprocessorEnvironment> c, final Scan scan,
    final RegionScanner s) throws IOException {
    ctPostScannerOpen.incrementAndGet();
    return s;
  }
A sample region observer that tests the RegionObserver interface. It works with
TestRegionObserverInterface to provide the test case.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/SimpleRegionObserver.java