public void postCompletedMergeRegionsAction(final RegionInfo[] regionsToMerge,
    final RegionInfo mergedRegion, final User user) throws IOException {
    execOperation(coprocEnvironments.isEmpty() ? null : new MasterObserverOperation(user) {
      @Override
      public void call(MasterObserver observer) throws IOException {
        observer.postCompletedMergeRegionsAction(this, regionsToMerge, mergedRegion);
      }
    });
  }
Invoked after completing merge regions operation
@param regionsToMerge the regions to merge
@param mergedRegion   the new merged region
@param user           the user
hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterCoprocessorHost.java