custom filter

Custom Filter

How to add a envoy filter which titan currently does not support

• Note:
  • This is to provide an intermidiate solution before such filter to be supported by titan natively

Create a custom helm template function

Create a helm template function which contains the envoy filter configuration

• The name of function needs to be globally unique within the entire the umbrella chart deployment
• You can use values to provide the configuration input, see the exmaple below for detail

Example

{{- define "envoy.filters.http.custom_response_handling_for_console_app" }}
  {{- $config :=  .config | default dict }}
  {{- $customFilterEnabled :=  ternary $config.enabled true (hasKey $config "enabled") }}
  {{- if $customFilterEnabled }}
- name: custom-composite-filter
  typed_config:
    "@type": type.googleapis.com/envoy.extensions.common.matching.v3.ExtensionWithMatcher
    extension_config:
      name: composite
      typed_config:
        "@type": type.googleapis.com/envoy.extensions.filters.http.composite.v3.Composite
    xds_matcher:
      matcher_list:
        matchers:
        - predicate:
            single_predicate:
              input:
                name: request-headers
                typed_config:
                  "@type": type.googleapis.com/envoy.type.matcher.v3.HttpRequestHeaderMatchInput
                  header_name: :path
              value_match:
                prefix: "/oidc/redirect"   
          on_match:
            action:
              name: composite-action
              typed_config:
                "@type": type.googleapis.com/envoy.extensions.filters.http.composite.v3.ExecuteFilterAction
                typed_config:
                  name: envoy.filters.http.custom_response
                  typed_config:
                    "@type": type.googleapis.com/envoy.extensions.filters.http.custom_response.v3.CustomResponse
                    custom_response_matcher:
                      matcher_list:
                        matchers:
                        # Redirect to different upstream if the status code is 504.
                        - predicate:
                            single_predicate:
                              input:
                                name: "504_response"
                                typed_config: 
                                  "@type": type.googleapis.com/envoy.type.matcher.v3.HttpResponseStatusCodeMatchInput
                              value_match:
                                  exact: "504"                           
                          on_match:
                            action:
                              name: action
                              typed_config: 
                                "@type": type.googleapis.com/envoy.extensions.http.custom_response.local_response_policy.v3.LocalResponsePolicy
                                status_code: {{ $config.redirectStatusCode | default "302" }}
                                response_headers_to_add:
                                - header:
                                    key: "Location"
                                    value:  {{ $config.redirectLocation | default "/unKnowUri" | quote }}
  {{- end }}
{{- end }}

Update values.yaml of your helm chart to enable custom helm template function

titanSideCars:
  customTpls:
    envoy:
      filters:
      - name: envoy.filters.http.custom_response_handling_for_console_app
        config:
          redirectStatusCode: "302"
          redirectLocation: ""/cc/loginError?loginError=4"