public String getLog() {
    return loggers.stream()
      .map(Object::toString)
      .collect(Collectors.joining(""))
      .replaceAll(System.lineSeparator() + "\\s*", System.lineSeparator() + "    ");
  }
Adds the CPU utilization since last log of every thread in a {@link Worker} pool to output.
planetiler-core/src/main/java/com/onthegomap/planetiler/stats/ProgressLoggers.java