private void notifyChangedReadersObservers(List<HStoreFile> sfs) throws IOException {
    for (ChangedReadersObserver o : this.changedReaderObservers) {
      List<KeyValueScanner> memStoreScanners;
      this.storeEngine.readLock();
      try {
        memStoreScanners = this.memstore.getScanners(o.getReadPoint());
      } finally {
        this.storeEngine.readUnlock();
      }
      o.updateReaders(sfs, memStoreScanners);
    }
  }
Notify all observers that set of Readers has changed.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HStore.java