@Override
  public void postCompact(ObserverContext<? extends RegionCoprocessorEnvironment> c, Store store,
    StoreFile resultFile, CompactionLifeCycleTracker tracker, CompactionRequest request)
    throws IOException {
    ctPostCompact.incrementAndGet();
  }
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