public String preModifyTableStoreFileTracker(final TableName tableName, final String dstSFT)
    throws IOException {
    if (coprocEnvironments.isEmpty()) {
      return dstSFT;
    }
    return execOperationWithResult(
      new ObserverOperationWithResult<MasterObserver, String>(masterObserverGetter, dstSFT) {
        @Override
        protected String call(MasterObserver observer) throws IOException {
          return observer.preModifyTableStoreFileTracker(this, tableName, getResult());
        }
      });
  }
@return An instance of MasterServices, an object NOT for general user-space Coprocessor
        consumption.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterCoprocessorHost.java