public void preOpen() throws IOException {
    if (coprocEnvironments.isEmpty()) {
      return;
    }
    execOperation(new RegionObserverOperationWithoutResult() {
      @Override
      public void call(RegionObserver observer) throws IOException {
        observer.preOpen(this);
      }
    });
  }
Invoked before a region open.
@throws IOException Signals that an I/O exception has occurred.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RegionCoprocessorHost.java