code: public boolean reloadAllocsIfNecessary() {
      if (allocFile == null) {
        // A warning has been logged when allocFile is null.
        // We should just return here.
        return false;
      }
      long time = System.currentTimeMillis();
      boolean reloaded = false;
      if (time > lastReloadAttempt + ALLOC_RELOAD_INTERVAL) {
        lastReloadAttempt = time;
        try {
          File file = new File(allocFile);
          long lastModified = file.lastModified();
          if (lastModified > lastSuccessfulReload &&
              time > lastModified + ALLOC_RELOAD_WAIT) {
            reloadAllocs();
            reloaded = true;
            lastSuccessfulReload = time;
            lastReloadAttemptFailed = false;
          }
        } catch (Exception e) {
          // Throwing the error further out here won't help - the RPC thread
          // will catch it and report it in a loop. Instead, just log it and
          // hope somebody will notice from the log.
          // We log the error only on the first failure so we don't fill up the
          // JobTracker's log with these messages.
          if (!lastReloadAttemptFailed) {
            LOG.error("Failed to reload allocations file - " +
                "will use existing allocations.", e);
          }
          lastReloadAttemptFailed = true;
        }
      }
      return reloaded;
    }
docs: Reload allocations file if it hasn't been loaded in a while
  return true if reloaded