How to intercept requests with lua script in Istio service mesh

Add custom header to the responses comming out the given Kubernetes application

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: add-custom-header-envoyfilter
  namespace: istio-system
spec:
  workloadSelector:
    labels:
      app: httpd-proxy
  configPatches:
  - applyTo: HTTP_FILTER
    match:
      context: SIDECAR_INBOUND
      listener:
        # portNumber: 80
        filterChain:
          filter:
            name: envoy.filters.network.http_connection_manager
            subFilter:
              name: envoy.filters.http.router
    patch:
      operation: INSERT_BEFORE
      value:
        name: envoy.filters.http.lua
        typed_config:
          "@type": "type.googleapis.com/envoy.extensions.filters.http.lua.v3.Lua"
          inlineCode: |
            function envoy_on_response(response_handle)
              response_handle:logDebug("Adding custom header to the response")
              response_handle:headers():add("X-Custom-Header", "1.2.3.4")
            end

The above works on the response. To modify the Lua `inlineCode` should look like this

  function envoy_on_request(request_handle)
  	request_handle:logInfo("Received request for " .. request_handle:headers():get(":path"))
  end

Note that by default the istio logging level is set to warning. You need to turn loggin to info to make it appear in the log file.