When we use a "simple fanout" Ingress pattern, as described here: https://v1-18.docs.kubernetes.io/docs/concepts/services-networking/ingress/#simple-fanout (we're using v1.18), the Ingress performs a simple redirect, sending 302 - Found
This causes the HTTP method to change to GET.
I'm trying to get the Ingress to give either a 307 or a 308 response instead.
I've tried using NGINX/k8s annotations, and I've tried applying the sort of approach here: https://stackoverflow.com/questions/56177198/kubernetes-nginx-ingress-changes-http-request-from-a-post-to-a-get but this doesn't work
We have 2 applications mapped to the same server using different ports behind the scenes.
Strangely enough, the POST is preserved fine with curl
In the end it's not really anything to do with K8S or NGINX:
The endpoint I wanted to use was mapped to "/" in the context (i.e. /blah/)
Since it's an API, it would be unusual to have something with a trailing slash, so I was referring to it by /blah, which the underlying application server rewrote to /blah/ with a 302.
Fixed it by using /v1 as the context (and ingress path), so I can have /v1/blah and it won't rewrite/redirect.