code: public void signalReady(Constraints viewConstraints) {
      try {
        rootFileSystem.mkdirs(signalDirectory);
      } catch (IOException e) {
        throw new DatasetIOException("Unable to create signal manager directory: "
                + signalDirectory, e);
      }
  
      String normalizedConstraints = getNormalizedConstraints(viewConstraints);
  
      Path signalPath = new Path(signalDirectory, normalizedConstraints);
      try{
        // create the output stream to overwrite the current contents, if the directory or file
        // exists it will be overwritten to get a new timestamp
        FSDataOutputStream os = rootFileSystem.create(signalPath, true);
        os.close();
      } catch (IOException e) {
        throw new DatasetIOException("Could not access signal path: " + signalPath, e);
      }
    }
docs: Create a signal for the specified constraints.
  
  @param viewConstraints The constraints to create a signal for.
  
  @throws DatasetException if the signal could not be created.