A load balancer/reverse proxy is the generally accepted solution to this, but be aware they have no concept of Ignition's specific redundancy concept. You'll have to use a product smart enough to distinguish between HTTP availability (whether the given redundant node is up at all) and Ignition's specific redundancy role (i.e. don't try to fail requests over to a backup that is not active). You can do this by checking the /system/gwinfo route.