Docs: Enable metrics in manifest-based deployments.

[piperubio]

What this PR does / why we need it:

This pull request improves the monitoring.md documentation by explicitly showing how to enable Prometheus metrics when deploying ingress-nginx using raw manifests.

Currently, the documentation only shows how to expose the Prometheus metrics port (10254) via the prometheus named port in the Deployment manifest. However, it omits the required argument --enable-metrics=true that actually enables nginx-specific metrics.

Without this argument, Prometheus can successfully scrape the /metrics endpoint, but it will only retrieve default Go and process-level metrics — not the nginx-related metrics such as HTTP requests, connections, or response codes. Adding --enable-metrics=true ensures that these nginx-specific metrics are computed and made available.

This clarification is particularly important for users not deploying via Helm.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• CVE Report (Scanner found CVE and adding report)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation only

Which issue/s this PR fixes

No specific issue opened, but it addresses a documentation gap related to Prometheus monitoring setup.

How Has This Been Tested?

The changes were validated by deploying ingress-nginx using the official manifests and confirming that Prometheus was able to scrape and display nginx-specific metrics from the exposed port 10254 after setting --enable-metrics=true.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added unit and/or e2e tests to cover my changes.
• All new and existing tests passed.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: piperubio / name: Felipe Rubio (547c753)

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[Gacko]

Please sign the CLA and apply the suggestions (or elaborate on why we need these characters) to get this PR merged. Thank you!

/retitle Docs: Enable metrics in manifest-based deployments.
/triage accepted
/kind documentation
/priority backlog
/hold

[piperubio]

Hi @Gacko ,

Thank you for your suggestions. The Contributor License Agreement (CLA) has already been signed.

Regarding the dots (...) in the code snippet, they are intentionally left to indicate that existing arguments should remain unchanged. For clarity—especially for less experienced users—it’s important to highlight that the monitoring argument should be appended to the existing list, not used as a replacement.

I sincerely apologize for the delayed response. I was disappointed to see that the pull request I submitted was closed, particularly since no alternative update to the monitoring documentation has been made by the maintainers, nor has a follow-up pull request been opened to address this addition. I still believe this change would be helpful to users deploying with raw manifests.

[Gacko]

You can still re-open or re-create it. I closed it because I didn't receive any feedback.

[Gacko]

/triage accepted
/kind documentation
/priority backlog
/lgtm

[Gacko]

/cherry-pick release-1.12

[k8s-infra-cherrypick-robot]

@Gacko: once the present PR merges, I will cherry-pick it on top of release-1.12 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.12

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[Gacko]

/cherry-pick release-1.11

[k8s-infra-cherrypick-robot]

@Gacko: once the present PR merges, I will cherry-pick it on top of release-1.11 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.11

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[Gacko]

/unhold

[Gacko]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Gacko, piperubio

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[k8s-infra-cherrypick-robot]

@Gacko: new pull request created: #13235

In response to this:

/cherry-pick release-1.12

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[k8s-infra-cherrypick-robot]

@Gacko: new pull request created: #13236

In response to this:

/cherry-pick release-1.11

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.