I'm using a 3rd-party API that invalidates the OAuth token if the requests came from different IP addresses. This is causing issues because the service runs on multiple hosts.
Ideally, I want the option that only the requests to this particular API will be routed through a single IP.
I thought about setting up a proxy server, but I'm concerned that I won't be able to scale this proxy beyond 1 machine.
Any suggestions?
The ideal option here would of course be to obtain an OAuth token for each machine. (Or, even better, to get the service to allow you to share a token across IPs.) But I assume there's some reason you can't do that.
In which case you probably do want a proxy server here.
The option that only the requests to this particular API be routed through that proxy is dead simple. Set up an explicit proxy rather than a transparent one, and specify that explicit proxy for these particular methods.
Since you haven't shown us, or even described, your code, I can't show you how to do that with whatever library you're using, but here's how to do it with requests, and it's not much harder with the stdlib urllib or most other third-party libraries.
But, for completeness: It's not at all impossible to make the separate machines appear to have the same IP address, as long as all of you machines are behind a router that you have control over. In fact, that's exactly what you get with a typical home DSL/cable setup via NAT: each machine has its own internal-only address, but they all share one public address. But it's probably not what you want. For one thing, if your machines are actually GCP hosts, you don't control the router, and you may not even be able to control whether they're on the same network (in case you were thinking of running a software router to pipe them all through). Also, NAT causes all kinds of problems for servers. And, since your worry here is scaling, using NAT is a nightmare once you have to scale beyond a single subnet. And even more so if these instances are meant to be servers (which seems likely, if you're running them on GCP). And finally, to use NAT to talk just to one service, you either need very complicated routing tables, or an extra network interface per machine (that you can put behind a different router). So, I doubt it's what you actually want here.