code: private void retireMapUnprotected(TaskInProgress tip) {
      if (runningMaps == null) {
        LOG.warn("Running cache for maps missing!! "
                 + "Job details are missing.");
        return;
      }
      runningMaps.remove(tip);
    }
docs: Remove a map TIP from the lists for running maps.
  Called when a map fails/completes (note if a map is killed,
  it won't be present in the list since it was completed earlier)
  @param tip the tip that needs to be retired