Right, SPARK_PUBLIC_DNS does not actually change the Akka hostname, it only changes the name we tell the user to use to access the master/worker, which is better than nothing. 

The actual hostname used by the Worker's Akka is specified in Utils.localIpAddressHostname, which unfortunately calls `InetAddress.getByName(address)`, transmuting the ip address into the container's ID as long as the /etc/hosts file exists. There is no current way to circumvent this behavior (there is a `Utils.setCustomHostname`, but it is only for testing purposes and cannot be specified by a configuration variable).