Istio Gateway EnvoyFilter

envoyfilter.yaml

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: edge-lua-filter
spec:
  workloadLabels:
    app: ingressgateway
  filters:
  - listenerMatch:
      portNumber: 443
      listenerType: GATEWAY
    filterName: envoy.lua
    filterType: HTTP
    filterConfig:
      inlineCode: |
        function process(request_handle, cluster, http_host)
            request_handle:logInfo("[" .. cluster .. "] Processing...")

            -- Build a request for our authenticaiton service before passing request upstream
            local authentication_request = {
                [":method"] = "POST",
                [":path"] = "{{ path }}",
                [":authority"] = {{ auth_host }},
            }
            
            local response_headers, response_body = request_handle:httpCall(
                cluster,
                authentication_request,
                "",                             -- empty body
                edge_processors_timeout_ms
            )

            -- If we don't get a 204 from our Authentication service, reject the request
            if tonumber(response_headers[":status"]) ~= 204 then
                request_handle:logInfo("[" .. cluster .. "] Failed")
                request_handle:respond(
                                {[":status"] = response_headers[":status"]},
                                response_body
                        )
            end

            -- The authentication service responds with a series of headers to Set and Unset
            -- Pass all 'Set-*' headers to upstream
            -- Remove all 'Unset-*' headers from request
            for header, value in pairs(response_headers) do
                local set_header = header:lower():match("^set%-(.+)")
                if set_header then
                    request_handle:headers():replace(set_header, value)
                else
                    local unset_header = header:lower():match("^unset%-(.+)")
                    if unset_header then
                        request_handle:headers():remove(unset_header)
                    end
                end
            end

            request_handle:logInfo("[" .. cluster .. "] Processed")
        end

        -- Called on the request path.
        function envoy_on_request(request_handle)
            process(request_handle, "{{ cluster }}", "{{ http_host }}")
        end

        -- Called on the response path.
        function envoy_on_response(response_handle)
            local headers = response_handle:headers()
            headers:add("X-Envoy-Ingress", os.getenv("HOSTNAME"))
        end

Thanks for the response @oahayder. I will do modify it accordingly. I have a question on cluster parameter to process() function. I would like to know what will be the value of that parameter. I have mentioned "outbound_.80_._.microservice.microservicens.svc.cluster.local" here as a value but it belongs to particular microservice. But I want these to be any calls to be processed for all calls to my Istio IG. If so what would be value of this 'cluster' parameter

gateway crash when client keep sending requests, any idea to limit the incoming requests ?
istio/istio#23874