Add process and go runtime metrics for controller

[mindw]

Pull Request Motivation

These metrics are default when using Prometheus go client's pre-defined registry, but were missing as the controller creates it's own registry.

Useful many debug scenarios

Kind

feature

Release Note

Add process and go runtime metrics for controller

[cert-manager-prow]

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[cert-manager-prow]

Hi @mindw. Thanks for your PR.

I'm waiting for a cert-manager member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[SgtCoDFish]

/ok-to-test

[cert-manager-prow]

@mindw: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cert-manager-master-make-test	c19108f	link	true	/test pull-cert-manager-master-make-test

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[wallrj]

Thanks @mindw

I deployed this and used https://grafana.com/grafana/dashboards/6671-go-processes/ to visualize the resulting metrics:

I can see that these metrics will be useful to the cert-manager team for optimizing cert-manager.
I'd be interested to learn how you might use these metrics in your platform.
Maybe you could write a short paragraph describing the user-story.

Do you think there's any risk to adding ~200 new metrics?
Might it cause any extra cost for people who are already monitoring cert-manager using a commercial monitoring service?

[wallrj]

Suggest rewording this comment to explain why rather than what the following code does.
Perhaps:

We want to avoid using and mutating global state so we avoid
prometheus.DefaultRegisterer. Instead we create a local Registry and manually register
the same two collectors that are used by DefaultRegisterer.

Process collector

Exports the current state of process metrics including CPU, memory and file
descriptor usage as well as the process start time. The detailed behavior is
defined by the provided ProcessCollectorOpts. The zero value of
ProcessCollectorOpts creates a collector for the current process with an empty
namespace string and no error reporting.

The collector only works on operating systems with a Linux-style proc
filesystem and on Microsoft Windows. On other operating systems, it will not
collect any metrics.

Go collector

Exports metrics about the current Go process using debug.GCStats (base
metrics) and runtime/metrics.

[wallrj]

Add a comment to the code explaining why we omit the godebug metrics.
And give an example of the metrics that will not be available.

OR

Remove that line and include all the Go metrics.

The DefaultRegisterer doesn't omit them.
Nor could I find any examples of other Go processes that omit these.

• https://github.com/prometheus/client_golang/blob/main/prometheus/registry.go#L60-L62
• https://github.com/letsencrypt/boulder/blob/5be3650e564e9fbc3492f2ff17678fdf9476efd7/cmd/shell.go#L262-L265
• https://github.com/istio/istio/blob/3b01bc01992b64c5d7710fbe0e32c74aca925170/pilot/cmd/pilot-agent/status/server.go#L163-L166
• https://github.com/search?q=repo%3Acilium%2Fcilium%20NewGoCollector&type=code
• https://github.com/cloudflare/pint/blob/af68e2a13dc46e87688752c4a96d9f81ec78b870/cmd/pint/watch.go#L170-L173

I tried removing that line and observed ~75 extra lines in the metrics.

$ kubectl get --raw /api/v1/namespaces/cert-manager/services/cert-manager:9402/proxy/metrics | wc -l
395

# Vs
$ kubectl get --raw /api/v1/namespaces/cert-manager/services/cert-manager:9402/proxy/metrics  | wc -l
470

And 25 extra metrics:

$ kubectl get --raw /api/v1/namespaces/cert-manager/services/cert-manager:9402/proxy/metrics  | grep '^go_godebug_'
go_godebug_non_default_behavior_execerrdot_events_total 0
go_godebug_non_default_behavior_gocachehash_events_total 0
go_godebug_non_default_behavior_gocachetest_events_total 0
go_godebug_non_default_behavior_gocacheverify_events_total 0
go_godebug_non_default_behavior_gotypesalias_events_total 0
go_godebug_non_default_behavior_http2client_events_total 0
go_godebug_non_default_behavior_http2server_events_total 0
go_godebug_non_default_behavior_httplaxcontentlength_events_total 0
go_godebug_non_default_behavior_httpmuxgo121_events_total 1
go_godebug_non_default_behavior_installgoroot_events_total 0
go_godebug_non_default_behavior_jstmpllitinterp_events_total 0
go_godebug_non_default_behavior_multipartmaxheaders_events_total 0
go_godebug_non_default_behavior_multipartmaxparts_events_total 0
go_godebug_non_default_behavior_multipathtcp_events_total 0
go_godebug_non_default_behavior_panicnil_events_total 0
go_godebug_non_default_behavior_randautoseed_events_total 0
go_godebug_non_default_behavior_tarinsecurepath_events_total 0
go_godebug_non_default_behavior_tls10server_events_total 0
go_godebug_non_default_behavior_tlsmaxrsasize_events_total 0
go_godebug_non_default_behavior_tlsrsakex_events_total 0
go_godebug_non_default_behavior_tlsunsafeekm_events_total 0
go_godebug_non_default_behavior_x509sha1_events_total 0
go_godebug_non_default_behavior_x509usefallbackroots_events_total 0
go_godebug_non_default_behavior_x509usepolicies_events_total 0
go_godebug_non_default_behavior_zipinsecurepath_events_total 0

$ kubectl get --raw /api/v1/namespaces/cert-manager/services/cert-manager:9402/proxy/metrics  | grep '^go_godebug_' | wc -l
25

[wallrj]

/kind feature

[mindw]

@wallrj Thank you for the detailed review and questions!
A bit low on free cycles ATM, hopefully I'll have enough till the end of next week.