code: private void dumpRecentInvalidateSets(PrintWriter out) {
      int size = recentInvalidateSets.values().size();
      out.println("Metasave: Blocks " + pendingDeletionBlocksCount
        + " waiting deletion from " + size + " datanodes.");
      if (size == 0) {
        return;
      }
      for (Map.Entry<String, LightWeightHashSet<Block>> entry : recentInvalidateSets
          .entrySet()) {
        LightWeightHashSet<Block> blocks = entry.getValue();
        if (blocks.size() > 0) {
          out.println(datanodeMap.get(entry.getKey()).getName() + blocks);
        }
      }
    }
docs: dumps the contents of recentInvalidateSets