I am following along this article and try this on GKE. After adding the argument - --log_output_level=default:debug the change seems accepted as I get deployment.extensions/istio-sidecar-injector edited , but I how do I know for sure?
The output of pod=$(kubectl -n istio-system get pods -l istio=sidecar-injector -o jsonpath='{.items[0].metadata.name}') and then kubectl -n istio-system logs -f $pod is the same as before and when I do (again)kubectl -n istio-system edit deployment istio-sidecar-injector the added argument is not there...
Depends on how installed Istio on GKE. There are multiple ways to install Istio from GKE.
If you're installing from http://cloud.google.com/istio which installs a Google-managed version of istio to your cluster, editing like kubectl -n istio-system edit deployment istio-sidecar-injector is a really bad idea, because Google will either revert it or the next version will wipe your modifications (so don't do it).
If you're installing yourself from Istio open source release, Istio is distributed as a Helm chart, and has bunch of kubernetes .yaml manifests. You can go edit those YAML manifests –or update Helm values.yaml files to add that argument. Then you can perform the Istio installation with the updated values.
If you're interested in getting help debugging istio, please get to a contributor community forum like Istio on Rocket Chat: https://istio.rocket.chat/ .