code: public static String drpcPids(Map conf) throws IOException {
          String ret = drpc_local_dir(conf) + FILE_SEPERATEOR + "pids";
          try {
              FileUtils.forceMkdir(new File(ret));
          } catch (IOException e) {
              LOG.error("Failed to create dir " + ret, e);
              throw e;
          }
          return ret;
      }
docs: Return drpc's pid dir