title: withFallback keyword when using akka
body: <p>What does the pattern keyword withFallback stands for and how is it used.</p>
  
  <p>Can someone help with this syntax and maybe provide some examples.</p>
  
  <p>How be the call to withFallback used?</p>
  
  <pre><code>object Worker extends App {
    val config =
      (if (args.nonEmpty) ConfigFactory.parseString(s"akka.remote.netty.tcp.port=${args(0)}")
      else ConfigFactory.empty).withFallback(
        ConfigFactory.parseString("akka.cluster.roles = [worker]")).
        withFallback(ConfigFactory.load())
  
    val system = ActorSystem("ClusterSystem", config)
    val worker = system.actorOf(Props(new Worker), name = "worker")
  
  }
  </code></pre>
  
  <p>Can you provide other examples of using it?</p>