istio envoyfilter lua to do some logging

Sometimes for doing troubleshooting, we need to create an envoyfilter to logs certain responses or headers related data. To do so we can use the following example:- 

apiVersion: networking.istio.io/v1alpha3

kind: EnvoyFilter

metadata:

  name: log-headers

  namespace: default

spec:

  workloadSelector:

    labels:

      app: httpbin

  configPatches:

  - applyTo: HTTP_FILTER

    match:

      context: SIDECAR_INBOUND

    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_request(request_handle)

              request_handle:logInfo("Hey hey hey: " .. request_handle:headers():get(":path"))

            end

Noticed that the envoy is scope to default namespace and not istio-system. If you placed this in istio-system, then you are applying it to the entire workload.

You might need to use "istioctl pc log httpbin-b5f55c9db-sh8hx --level=debug" to give it a kick, otherwise the log might stay hidden.

To view your logs, simply 

k logs httpbin-b5f55c9db-sh8hx -n default -c istio-proxy -f  | findstr "Hey hey"