private void allWorkersFinished(Phase phase) {
    var timer = startTimes.get(phase);
    if (timer != null) {
      timer.stop();
    }
    String summary = getSummary(phase);
    if (summary != null) {
      LOGGER.info("Finished " + getSummary(phase));
    }
  }
Creates a new phaser expecting a certain number of workers to register.
planetiler-core/src/main/java/com/onthegomap/planetiler/reader/osm/OsmPhaser.java