[Question] How can I insert a HTTP header only when that header does not exist?

[SpecialYang]

For example, I want to add a HTTP header foo: bar into request when the original request does not have the HTTP header foo. But, if the original request have the HTTP header foo, envoy should do nothing header manipulation for this request.

The existing setting HeaderValueOption can't resolve this issue. Please correct me if i am wrong.

CC @wbpcode

[wbpcode]

Hmm, yeah, although the new option was added in the #18246, the implementation is still absent.

[wbpcode]

I will try to land it.

[soulxu]

A workaround should be able to do that for now before @wbpcode land it

              routes:
              - match:
                  prefix: "/"
                  headers:
                  - name: "foo"
                    present_match: false
                route:
                  cluster: my_cluster
                request_headers_to_add:
                - header:
                    key: foo
                    value: bar
              - match:
                  prefix: "/"
                  headers:
                  - name: "foo"
                    present_match: true
                route:
                  cluster: my_cluster

[SpecialYang]

A workaround should be able to do that for now before @wbpcode land it

              routes:
              - match:
                  prefix: "/"
                  headers:
                  - name: "foo"
                    present_match: false
                route:
                  cluster: my_cluster
                request_headers_to_add:
                - header:
                    key: foo
                    value: bar
              - match:
                  prefix: "/"
                  headers:
                  - name: "foo"
                    present_match: true
                route:
                  cluster: my_cluster

Thank you. But it is difficult for the scale deployment.

[soulxu]

A workaround should be able to do that for now before @wbpcode land it

              routes:
              - match:
                  prefix: "/"
                  headers:
                  - name: "foo"
                    present_match: false
                route:
                  cluster: my_cluster
                request_headers_to_add:
                - header:
                    key: foo
                    value: bar
              - match:
                  prefix: "/"
                  headers:
                  - name: "foo"
                    present_match: true
                route:
                  cluster: my_cluster

Thank you. But it is difficult for the scale deployment.

np! yea, that could be a combination explosion.