Unable to collect metrics from customized fluentd

[PChenSE]

Hi,
I have troubles to enable metrics on my GKE after customized fluentd in another namespace.
I add some changes to the fluentd configmap, since GKE default fluentd & configmap in kube-system namespace can't change(changes always get reverted), I deployed the fluentd and event-exporter in another namespace.

But the metrics are missing after I made the change. All the logs are OK, the customized fluentd works.

What needs to be done so GKE can collect the metrics again? Or maybe I'm wrong, is there any way to modify the default fluentd-configmap in the kube-system?