Fly-Instance-Id header alternative for websockets

[ignoramous]

@mdj

It’s a bit a stretch, but is there a way to target a specific instance using DNS

One could create multiple apps (each get their own IP), and plonk the IPs in any number of DNS A/AAAA/HTTPS/SVCB records as you see fit (1).

One could run one server per region, assign them regional IPs, and map those to DNS records (2).

One can run app over multiple Machines (which, for now, each get a fixed public IPv6 address) (3).

Anchor scaling also helps keep public IPv6 stable for regular Fly app instances, but I see references to it have been removed from docs. Anyways, ref: (4).

One could route traffic to a set of front-end app instances that then forward it to appropriate back-end app instance:

1. Either connect back-end and front-end instances over 6pn (5, 6).
2. Or, relay traffic with Fly’s HTTP handlers (unlikely to work with websockets, I’d assume) (7).