As an example, if we look at https://github.com/GoogleCloudPlatform/container-vm-guestboo... then there are a couple of things here that are IPv4 only. The first is that the application is only configured to listen on the IPv4 address family, app.run(host='0.0.0.0', port=80), on linux if that was changed to app.run(host='::', port=80) this the application would be able to receive both IPv4 and IPv6 requests (on windows the situation is different however)
The second, and less important change, is that the redis connection is using 127.0.0.1, and if instead it was using "localhost" then that would resolve to the correct address family. This is less important as it is only relevant if there is no IPv4 on the server host, the first change would allow your app to accept IPv6 traffic.
Neither of these changes are required if there is a dual stack proxy or CDN that sits infront of your application, as they will most likely talk to your application over IPv4.
The other gotcha is if you try to interrogate clientIP for analytics, authorization, geo-ip etc, which may need a little more care.
Neither of these changes are required if there is a dual stack proxy or CDN that sits infront of your application, as they will most likely talk to your application over IPv4.
The other gotcha is if you try to interrogate clientIP for analytics, authorization, geo-ip etc, which may need a little more care.