Envoy: Using Local reply modification

[karthequian]

How do you use the Local Reply Modification feature?

I was reading about the local reply modification feature: https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_conn_man/local_reply.html?highlight=mapper and was looking to add the mapper to change the HTTP Response text that would be returned in a fault scenario.

mappers:
- filter:
    status_code_filter:
      comparison:
        op: EQ
        value:
          default_value: 400
          runtime_key: key_b
  headers_to_add:
    - header:
        key: "foo"
        value: "bar"
      append: false
  status_code: 401
  body:
    inline_string: "not allowed"

However, I'm not sure where to add this in the envoy config. I've tried adding this to the top level of envoy.filters.network.http_connection_manager, but I don't think it's the right spot for it, and wasn't sure how to add it to the http_filters section.

I keep getting the following error:

Protobuf message (type envoy.config.bootstrap.v3.Bootstrap reason INVALID_ARGUMENT:(static_resources.listeners[0].filter_chains[0].filters[0]) mappers: Cannot find field.) has unknown fields

Any help would be appreciated, and I can go back to update the docs to make it clearer if needed!

[mk46]

@karthequian I think you're adding it to the wrong place. HCM has local_reply_config and config should be added like below.

filter_chains:
    - filters:
      - name: envoy.filters.network.http_connection_manager
        typed_config:
          "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
          codec_type: auto
          stat_prefix: ingress_http
          route_config:
            name: local_route
          http_filters:
          - name: envoy.filters.http.router
            typed_config: {}
          local_reply_config:
            mappers:
            - filter:
                status_code_filter:
                  comparison:
                   op: EQ
                   value:
                     default_value: 400
                     runtime_key: key_b
              headers_to_add:
                - header:
                    key: "foo"
                    value: "bar"
                  append: false
              status_code: 401
              body:
                inline_string: "not allowed"

[karthequian]

Thank you so much @mk46! Really useful to see the whole config. Will try it today and close this issue!

[mk46]

Hi @karthequian, LMK if you still facing any issue with configuration otherwise we should close this.