Metrics: Fix nginx_ingress_controller_config_last_reload_successful.

[raorudzhov]

What this PR does / why we need it:

This patch fixes an issue in the NGINX Ingress Controller where invalid Ingress resources caused metric nginx_ingress_controller_config_last_reload_successful to be set value to 0 and never restored after the resource was deleted.

With this change, metrics are now correctly updated even if an Ingress is removed, or its configuration is invalid.

This ensures that monitoring data remains consistent and accurate.

🪲 P.S. this PR also resolved Issue#13818

Previously, when an Ingress contained misconfigurations (e.g. invalid annotations or unsupported snippet directives), the following problems occurred:

1. Metrics such as nginx_ingress_controller_config_last_reload_successful were set to 0.
2. After deleting the invalid Ingress, metrics stayed at 0 instead of being restored to 1.
3. Some parts of the syncIngress logic were skipped due to an early Equal check, preventing proper metric updates.

As a result:

• Metrics did not reflect the real state of the controller.
• Monitoring systems could generate false alerts.
• Operators had no reliable signal that the system had recovered after removing a faulty Ingress.

This patch resolves those issues by ensuring metrics are always properly updated, regardless of Ingress validity.

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

This PR fixed Issue#13818

How Has This Been Tested?

1. Create an invalid Ingress resource;

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app-ingress
  namespace: default
  annotations:
    nginx.ingress.kubernetes.io/configuration-snippet: |
      bla-bla-bla
spec:
  ingressClassName: nginx
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp
                port:
                  number: 80

2. See in logs that NGINX complains about invalid configuration;

Error reloading NGINX:
-------------------------------------------------------------------------------
Error: exit status 1
nginx: [emerg] unknown directive "bla-bla-bla" in /tmp/nginx/nginx-cfg3530923120:6208
nginx: configuration file /tmp/nginx/nginx-cfg3530923120 test failed
-------------------------------------------------------------------------------

3. Check metrics inside the pod, value is 0;

curl 127.0.0.1:10254/metrics -s | grep reload_successful{
nginx_ingress_controller_config_last_reload_successful{controller_class="ingress-nginx.deckhouse.io/nginx",controller_namespace="d8-ingress-nginx",controller_pod="controller-nginx-rwmf5"} 0

4. Delete the invalid Ingress resource;
5. Check metrics again, value is should be 1.

curl 127.0.0.1:10254/metrics -s | grep reload_successful{
nginx_ingress_controller_config_last_reload_successful{controller_class="ingress-nginx.deckhouse.io/nginx",controller_namespace="d8-ingress-nginx",controller_pod="controller-nginx-rwmf5"} 1

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.

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• ✅ login: raorudzhov / name: Roman Orudzhov (2d2f0a6)

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[k8s-ci-robot]

Hi @raorudzhov. 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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[Gacko]

/triage accepted
/kind cleanup
/priority backlog
/hold

Do you think it's possible to test this in either unit tests or E2E tests (or both)?

[Gacko]

/cherry-pick release-1.13

[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-1.13 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.13

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: 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

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.

[raorudzhov]

Most likely, the current e2e tests don’t cover this, but if we add handling for this scenario, the functionality will most likely be covered.

[Gacko]

I'm not that deep in our E2E tests, Go code wise, but I can imagine them to be able to do something like "use invalid config, check the metric is 0, fix config, check the metric is 1". That would be enough!

Also I'd like to have the expected behavior written down somewhere, so in tests, also to be able to prevent any regression.

[raorudzhov]

Got it! Just to clarify — do you want me to expand this with actual E2E test cases? So that you can accept PR

[Gacko]

Exactly, that would be wonderful! I'm currently about to start a new release cycle, so if you hurry this would still make it into a v1.13.2 / v1.12.6. 🙂

[Gacko]

So, I took a deeper look and I think it's hard to impossible to test this, because this needs an invalid Ingress to recover from and currently configuring Ingress resources in E2E tests always waits for the controller and NGINX to have been reloaded. I'm gonna test this manually for now.

[Gacko]

/triage accepted
/kind bug
/priority backlog
/hold
/ok-to-test

Ok, I tested the current main with and without your change and a) you're right, it's not working without and b) your change fixes it. As stated before I currently have hard times believing this can be covered by tests as these wait for the reload to succeed after a configuration change and I do not have the resources to extend our testing framework for this use-case at the moment.

Let me just bump some images I promoted today, then I will merge your PR and kick of the controller build for the next patch release.

[raorudzhov]

Thank you for your help
I’ll be waiting for the merge

[Gacko]

/lgtm
/unhold

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[k8s-infra-cherrypick-robot]

@Gacko: new pull request created: #13859

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: #13860

In response to this:

/cherry-pick release-1.13

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.