[stable/prometheus-blackbox-exporter] Fix blackbox target's metrics labels

[mcanevet]

The metrics labels currently generated does not match what is generated
by the setup described here: https://prometheus.io/docs/guides/multi-target-exporter/#querying-multi-target-exporters-with-prometheus
and https://github.com/prometheus/blackbox_exporter#prometheus-configuration

The previous metricsRelabeling is only valid if the target contains the URLs to
check.

What we need in the end is:

• __address__ set to the blackbox exporter, and it it already the case
  as the selector matches the blackbox exporter,
• __param_target set to the target to check, and it is already ensure
  without relabeling,
• instance set to the target to check.

This patches ensures that the metrics has this labels:

probe_success{endpoint="http",instance="http://prometheus.io",job="blackbox-exporter-prometheus-blackbox-exporter",namespace="monitoring",pod="blackbox-exporter-prometheus-blackbox-exporter-84d9b64646-vgqcc",service="blackbox-exporter-prometheus-blackbox-exporter",target="prometheus-io"} 1

Without this patch, we have this (note that we lost the instance label):

probe_success{endpoint="http",job="blackbox-exporter-prometheus-blackbox-exporter",namespace="monitoring",pod="blackbox-exporter-prometheus-blackbox-exporter-84d9b64646-vgqcc",service="blackbox-exporter-prometheus-blackbox-exporter",target="prometheus-io"} 1

Signed-off-by: Mickaël Canévet mickael.canevet@gmail.com

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• DCO signed
• Chart Version bumped
• Variables are documented in the README.md
• Title of the PR starts with chart name (e.g. [stable/mychartname])

[k8s-ci-robot]

Hi @mcanevet. Thanks for your PR.

I'm waiting for a helm 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[zanhsieh]

/ok-to-test

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Any further update will cause the issue/pull request to no longer be considered stale. Thank you for your contributions.

[desaintmartin]

Sorry, I didn't have time to investigate but this looks interesting, I'll try to find time to review/test.
/assign

[desaintmartin]

Okay, I've read a bit more about that and you seem to be right, however doing so would remove the "human readable name" that was set to the target label. Could we keep target but also add instance?

[mcanevet]

@desaintmartin I updated my PR to keep the target label.

[desaintmartin]

Thanks! One last thing, could you fill the "how to upgrade" paragraph for the 5.0.0?

[mcanevet]

@desaintmartin done!

[desaintmartin]

Thanks a lot!
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: desaintmartin, mcanevet

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