How to correctly determine the closest server file to the client?

Question

CDN

There are several servers on which the same file.
The user makes a request. you need to check out the files from the nearest server.
Constantly using IP to determine the location can fail, because the IP is not always correct or there is one at all.
If, nevertheless, there is an IP, it is unprofitable to determine the location each time by external geo ip services for each request.
As well as calculating the nearest server each time, because you need to ping everything to determine which is the best.
How to implement this correctly?

Answer 1

It's probably worth looking into the Border gateway protocol. This thing allows you to find the shortest path in the network. And then - geodns