def main()

in pekko-sample-sharding-scala/killrweather/src/main/scala/sample/killrweather/KillrWeather.scala [15:38]

• 16 lines of code
• 5 McCabe index (conditional complexity)

  def main(args: Array[String]): Unit = {
    val seedNodePorts = ConfigFactory.load().getStringList("pekko.cluster.seed-nodes")
      .asScala
      .flatMap { case AddressFromURIString(s) => s.port }

    // Either use a single port provided by the user
    // Or start each listed seed nodes port plus one node on a random port in this single JVM if the user
    // didn't provide args for the app
    // In a production application you wouldn't start multiple ActorSystem instances in the
    // same JVM, here we do it to simplify running a sample cluster from a single main method.
    val ports = args.headOption match {
      case Some(port) => Seq(port.toInt)
      case None       => seedNodePorts ++ Seq(0)
    }

    ports.foreach { port =>
      val httpPort =
        if (port > 0) 10000 + port // offset from pekko port
        else 0 // let OS decide

      val config = configWithPort(port)
      ActorSystem[Nothing](Guardian(httpPort), "KillrWeather", config)
    }
  }