default void postFlush(ObserverContext<? extends RegionCoprocessorEnvironment> c,
    FlushLifeCycleTracker tracker) throws IOException {
  }
Called after the memstore is flushed to disk.
@param c       the environment provided by the region server
@param tracker tracker used to track the life cycle of a flush
@throws IOException if an error occurred on the coprocessor
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/RegionObserver.java