public void preShutdown() throws IOException {
    // While stopping the cluster all coprocessors method should be executed first then the
    // coprocessor should be cleaned up.
    if (coprocEnvironments.isEmpty()) {
      return;
    }
    execShutdown(new MasterObserverOperation() {
      @Override
      public void call(MasterObserver observer) throws IOException {
        observer.preShutdown(this);
      }

      @Override
      public void postEnvCall() {
        // invoke coprocessor stop method
        shutdown(this.getEnvironment());
      }
    });
  }
Invoked after rollback merge regions operation
@param regionsToMerge the regions to merge
@param user           the user
hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterCoprocessorHost.java