/**
  * Log task mapped.
  *
  * @param log Logger.
  * @param clazz Task class.
  * @param nodes Mapped nodes.
  */
 public static void logMapped(
     @Nullable IgniteLogger log, Class<?> clazz, Collection<ClusterNode> nodes) {
   log0(
       log,
       U.currentTimeMillis(),
       String.format("[%s]: MAPPED: %s", clazz.getSimpleName(), U.toShortString(nodes)));
 }
  /**
   * Log finished.
   *
   * @param log Logger.
   * @param clazz Class.
   * @param start Start time.
   */
  public static void logFinish(@Nullable IgniteLogger log, Class<?> clazz, long start) {
    final long end = U.currentTimeMillis();

    log0(
        log,
        end,
        String.format(
            "[%s]: FINISHED, duration: %s", clazz.getSimpleName(), formatDuration(end - start)));
  }
  /**
   * Log message.
   *
   * @param log Logger.
   * @param msg Message to log.
   * @param clazz class.
   * @param start start time.
   * @return Time when message was logged.
   */
  public static long log(@Nullable IgniteLogger log, String msg, Class<?> clazz, long start) {
    final long end = U.currentTimeMillis();

    log0(
        log,
        end,
        String.format(
            "[%s]: %s, duration: %s", clazz.getSimpleName(), msg, formatDuration(end - start)));

    return end;
  }
 /**
  * Log message.
  *
  * @param log Logger.
  * @param msg Message.
  */
 public static void log(@Nullable IgniteLogger log, String msg) {
   log0(log, U.currentTimeMillis(), " " + msg);
 }