code: private ExtractionGuard placeExtractionGuard(String path) {
          boolean isPrimary;
          CountDownLatch completionLatch;
  
          synchronized( extractionsLock ) {
              completionLatch = extractionLocks.get(path);
  
              if ( completionLatch != null ) {
                  isPrimary = false;
  
              } else {
                  isPrimary = true;
  
                  completionLatch = new CountDownLatch(1);
                  extractionLocks.put(path,  completionLatch);
              }
          }
  
          return new ExtractionGuard(path, isPrimary, completionLatch);
      }
docs: Make sure a completion latch exists for a specified path.
  
  Create and store one if necessary.
  
  Answer the completion latch encapsulated in an extraction latch,
  which brings together the completion latch with the path and
  with a setting of whether the extraction is a primary (doing
  the extraction) or secondary (waiting for the primary to do the
  extraction).
  
  @param path The path which is being extracted.
  
  @return An extraction latch for the path which encapsulates
  the extraction state (primary or secondary), the path,
  and the completion latch for the extraction.