Istio and the custom HTTP method - istio

Question

How to make Istio route custom HTTP methods?
$ curl -v -X MYMETHOD https://myapp.com
< HTTP/2 400
< content-length: 11
< content-type: text/plain
< date: Wed, 29 Dec 2021 08:24:36 GMT
< server: envoy
< x-envoy-upstream-service-time: 1
<
* Connection #0 to host myapp.com left intact
Bad Request
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
name: myapp
spec:
gateways:
- gw
hosts:
- 'myapp.com'
http:
- name: myapp
route:
- destination:
host: myapp
port:
number: 8000
Kubernetes: 1.22.4
Istio: 1.12.1

Answer 1

Envoy does not support custom HTTP methods. Envoy implements the H/1 codec, which has a hardcoded list of HTTP methods it accepts (see RFC)
There is an open issue on the Envoy Github: https://github.com/envoyproxy/envoy/issues/18819
So you can't achieve what you want with an HTTP route. But you can make it work with a TCP/TLS route.
For this do the following:
Set the correct protocol on the service istio-ingressgateway:
ports:
- name: tcp
nodePort: 8000
port: 8000
protocol: TCP
Change the protocol on the gateway port
port:
name: tcp-gateway
number: 8000
protocol: TCP
Configure your Virtual Service for TCP traffic:
spec:
gateways:
- example-gateway
hosts:
- myapp.com
tcp:
- match:
- port: 8000
route:
- destination:
host: myapp.svc.cluster.local
port:
number: 8000
With a TCP endpoint, you have to take into account that you can't apply host/path-based routing. So make sure your myappp VirtualService is the only service that serves that port.