We can monitor the kubeless function using Prometheus. There is in-built runtime support for Prometheus; the runtime will automatically collect metrics for each function. Prometheus will show those metrics on the default dashboard.
The Prometheus metrics can be visualized through Grafana. The Grafana dashboard can be configured through the sample dashboard JSON file provided by Kubeless at https://github.com/kubeless/kubeless/blob/master/docs/misc/kubeless-grafana-dashboard.json.