Fix prometheus metric in proxy utils

[marlongehringer]

Issue Ref:
#1020

Description:
I changed prometheus.NewHistogramVec to promauto.NewHistogramVec.
I also removed the MustRegister as it's not needed anymore.

I tested it and now I see all the function's metrics additionally to the Golang internal metrics.

Documentation of promauto:
https://godoc.org/github.com/prometheus/client_golang/prometheus/promauto

With that it should be ensured that the metrics are added everywhere.

TODOs:

• Ready to review
• Automated Tests
• Docs

[marlongehringer]

Seems like promauto was added in version 0.9.0 of client_golang.
https://github.com/prometheus/client_golang/releases/tag/v0.9.0

I will bump the version from 0.8.0 to 0.9.2.
Do we need additional testing here? The client_golang is only used in the proxy.

[marlongehringer]

Something went wrong... I did dep ensure after upgrading the version. Do you have an idea what is wrong? @andresmgot

[andresmgot]

It seems that when you ran dep ensure the Kubeless package got somehow downgraded. If you are only interested on updating prometheus/client_golang you can update that single package executing dep ensure -update github.com/prometheus/client_golang@0.9.2

[Shashankft9]

Hey @marlongehringer was this merged into the master?
Because I still don't see the the metrics for the go runtime while it is working swiftly for python runtime.

[marlongehringer]

Hi @Shashankft9, sorry for the inconvenience. It was not merged into master. I had some trouble with the dependencies and then totally forgot about it as the priority for me was gone.

You can check my changes in pkg/function-proxy/utils/proxy-utils.go and maybe create your own pull request. I will close my PR because I'm not using this anymore.