Golang runtime incomplete metrics due to proxy utils

[marlongehringer]

Is this a BUG REPORT or FEATURE REQUEST?:
FEATURE REQUEST

What happened:
Metrics like "function_calls_total" are missing in the prometheus endpoint in the golang runtime.

What you expected to happen:
Metrics in the golang runtime should be complete.

How to reproduce it (as minimally and precisely as possible):
curl http://127.0.0.1:8080/metrics

Anything else we need to know?:
https://github.com/kubeless/kubeless/blob/84fa853fa04bf69fe22326729fddfa95b0a0e9e4/pkg/function-proxy/utils/proxy-utils.go#L61

The proxy utils are executing the MustRegister only in the init() function which is not called in the golang runtime.

https://github.com/kubeless/runtimes/blob/bdee7792a6d265a719a75e886071cbc4fb5f7295/stable/golang/kubeless.tpl.go#L81

Easiest solution would be to move the MustRegister to a public function which we can call in the runtime. What do you think?

[andresmgot]

Thanks @marlongehringer for the issue, I was able to reproduce it. Actually the init() function is always executed when you import a Go package so the issue should be a different one. I think that the problem is that the two packages are instantiating a different prometheus client (one is using prometheus and the other promhttp) so that's probably the issue.

What may fix the issue is to either use the prometheus package in the Go runtime or expose it in the proxy-utils package with a function so the Go runtime doesn't need to import it. Would you be able to give it that try?

[marlongehringer]

You are right @andresmgot. I created a Pull-Request. Thanks for your quick reply.