EnvoyFilterUsesAddOperationIncorrectly

This message occurs when an EnvoyFilter uses the ADD operation and ApplyTo is set to ROUTE_CONFIGURATION or HTTP_ROUTE. This will cause the ADD operation to be ignored. At the moment only the MERGE operation can be used for ROUTE_CONFIGURATION.

An example

Consider an EnvoyFilter with the patch operation of ADD where this EnvoyFilter will just be ignored:

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: test-auth-2
  namespace: bookinfo
spec:
  configPatches:
  - applyTo: ROUTE_CONFIGURATION
    match:
      context: SIDECAR_INBOUND
    patch:
      operation: ADD
      filterClass: AUTHZ # This filter will run *after* the Istio authz filter.
      value:
        name: envoy.filters.http.ext_authz
        typed_config:
          "@type": type.googleapis.com/envoy.extensions.filters.http.ext_authz.v3.ExtAuthz
          grpc_service:
            envoy_grpc:
              cluster_name: acme-ext-authz
            initial_metadata:
            - key: foo
              value: myauth.acme # required by local ext auth server.