Custom option for gathering prometheus metrics for ingresses without host specified

[stephanepiel]

What this PR does / why we need it:

Add a command line option which allow to generate Prometheus metrics for ingress that do not have host specified. By default, option is not activated (no breaking change). When activated, it gives back same behavior as before version 0.20
It can be helpful when you have no host specified in ingresses but yet need related metrics (and there is no risk of DOS attacks when ingress controllers are not publicly accessible)

Relates to two issues (#3713 and #3844)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Which issue/s this PR fixes

fixes #3713
fixes #3844

How Has This Been Tested?

Tests added
Used for sometime in real environment

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added tests to cover my changes.
• All new and existing tests passed.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: stephanepiel
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[aledbf]

@stephanepiel I am sorry but we are not merging changes to the metrics until we can address the approach as a whole. Please check https://github.com/kubernetes/ingress-nginx/pull/4352/files

[stephanepiel]

@aledbf Too bad
Anyway, can you give us any insights about when this metric approach as a whole will be effective ? Next version ?

[richgerrard]

@stephanepiel I am sorry but we are not merging changes to the metrics until we can address the approach as a whole. Please check https://github.com/kubernetes/ingress-nginx/pull/4352/files

I see you closed the linked PR without merging. Can you revisit this now, please @aledbf ?
Thank you!

[aledbf]

I see you closed the linked PR without merging. Can you revisit this now, please @aledbf ?

I'm sorry. I reopened the PR.

[si-mmarcoux]

@stephanepiel Do you have a custom docker image with it implemented?
To be honest it would be great it's pretty critical for us, destroying all our metrics.

[stephanepiel]

Hello @crak-mmarcoux ,
We actually use a modified nginx-ingress-controller, as per this PR. Image was internally built, and is not publicly available as for now. I think we could publish it, I have to found a way to do it.

[fejta-bot]

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[k8s-ci-robot]

@stephanepiel: PR needs rebase.

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