Fixed /metrics endpoint for resource consumer

[aespejel]

What type of PR is this?

Uncomment only one, leave it on its own line:

/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:
Fixes the endpoint exposing metrics in the resource consumer container.
By default, and as far as I know, Prometheus looks for /metrics, right now metrics are being exposed on /Metrics (and the purpose of this endpoint, reading the docs, is to be able to expose fake metrics in Prometheus format on "/metrics").

Which issue(s) this PR fixes:

Fixes #72403

Special notes for your reviewer:
It was probably introduced here: 967a7c9

Does this PR introduce a user-facing change?:

NONE

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[k8s-ci-robot]

Hi @aespejel. Thanks for your PR.

I'm waiting for a kubernetes 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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[aespejel]

I signed it

[ixdy]

/ok-to-test

It was probably introduced here: 967a7c9

Nice catch! Though the e2e test that uses this image seems to use /Metrics now, not /metrics. So either this is working-as-intended (and the docs should be updated), or we'll also need to update the e2e test:

kubernetes/test/e2e/instrumentation/monitoring/prometheus.go

Lines 111 to 127 in 7d85546

	func exportCustomMetricFromPod(f *framework.Framework, consumerName string, metricValue int) *common.ResourceConsumer {
	podAnnotations := map[string]string{
	"prometheus.io/scrape": "true",
	"prometheus.io/path": "/Metrics",
	"prometheus.io/port": "8080",
	}
	return common.NewMetricExporter(consumerName, f.Namespace.Name, podAnnotations, nil, metricValue, f.ClientSet, f.InternalClientset, f.ScalesGetter)
	}
	func exportCustomMetricFromService(f *framework.Framework, consumerName string, metricValue int) *common.ResourceConsumer {
	serviceAnnotations := map[string]string{
	"prometheus.io/scrape": "true",
	"prometheus.io/path": "/Metrics",
	"prometheus.io/port": "8080",
	}
	return common.NewMetricExporter(consumerName, f.Namespace.Name, nil, serviceAnnotations, metricValue, f.ClientSet, f.InternalClientset, f.ScalesGetter)
	}

/assign @serathius

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In response to this:

/ok-to-test

It was probably introduced here: 967a7c9

Nice catch! Though the e2e test that uses this image seems to use /Metrics now, not /metrics. So either this is working-as-intended (and the docs should be updated), or we'll also need to update the e2e test:

kubernetes/test/e2e/instrumentation/monitoring/prometheus.go

Lines 111 to 127 in 7d85546

	func exportCustomMetricFromPod(f *framework.Framework, consumerName string, metricValue int) *common.ResourceConsumer {
	podAnnotations := map[string]string{
	"prometheus.io/scrape": "true",
	"prometheus.io/path": "/Metrics",
	"prometheus.io/port": "8080",
	}
	return common.NewMetricExporter(consumerName, f.Namespace.Name, podAnnotations, nil, metricValue, f.ClientSet, f.InternalClientset, f.ScalesGetter)
	}
	func exportCustomMetricFromService(f *framework.Framework, consumerName string, metricValue int) *common.ResourceConsumer {
	serviceAnnotations := map[string]string{
	"prometheus.io/scrape": "true",
	"prometheus.io/path": "/Metrics",
	"prometheus.io/port": "8080",
	}
	return common.NewMetricExporter(consumerName, f.Namespace.Name, nil, serviceAnnotations, metricValue, f.ClientSet, f.InternalClientset, f.ScalesGetter)
	}

/assign @serathius

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[ixdy]

also
/cc @jszczepkowski

[aespejel]

@ixdy
The default config of Prometheus when installed with helm (just did some days ago) has this:

- job_name: kubernetes-pods
  scrape_interval: 1m
  scrape_timeout: 10s
  metrics_path: /metrics
  scheme: http

So I guess that we should update the tests, if you don't mind I'll update it right now, and if finally we don't go this way and it's working as intended, we just close this PR and open other updating the docs. :)

[ixdy]

in order for the tests to pass, we'll need to update the version and push a new version of the image, too.

I'd like to get @jszczepkowski or @serathius to weigh in on the expected behavior before doing that.

[liggitt]

the approvers in https://github.com/kubernetes/kubernetes/blob/master/test/e2e/instrumentation/OWNERS can approve this change

[ixdy]

Can someone on @kubernetes/sig-instrumentation-pr-reviews please review?

[brancz]

/lgtm

[brancz]

/approve

[brancz]

/lgtm
/approve

[ixdy]

Can you please squash your commits? Otherwise this LGTM.

[aespejel]

Can you please squash your commits? Otherwise this LGTM.

@ixdy done!

[brancz]

/lgtm

[ixdy]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aespejel, brancz, ixdy

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