@Override
    public void postCompactSelection(ObserverContext<? extends RegionCoprocessorEnvironment> c,
      Store store, List<? extends StoreFile> selected, CompactionLifeCycleTracker tracker,
      CompactionRequest request) {
      if (selected != null) {
        filesCompactedCounter.increment(selected.size());
      }
    }
An example coprocessor that collects some metrics to demonstrate the usage of exporting custom
metrics from the coprocessor.
<p>
These metrics will be available through the regular Hadoop metrics2 sinks (ganglia, opentsdb,
etc) as well as JMX output. You can view a snapshot of the metrics by going to the http web UI of
the regionserver page, something like http://myregionserverhost:16030/jmx
</p>
@see ExampleMasterObserverWithMetrics
hbase-examples/src/main/java/org/apache/hadoop/hbase/coprocessor/example/ExampleRegionObserverWithMetrics.java