Lua: Fix ExternalName services without endpoints.

[neerfri]

Due to kubernetes/kubernetes#114814 kubernetes no longer creates endpoints for services of type ExternalService. This in turn causes an exception when using an ingress that is backed by such service.

Due to #12952 , which I authored, this causes an exception reported in several recent issues that were opened after the new functionality was released.

I'm still puzzled why the e2e tests in https://github.com/kubernetes/ingress-nginx/blob/main/test/e2e/servicebackend/service_externalname.go did not catch those problems on effected versions of Kubernetes.

This is also related to:

• Regression when using ExternalName services #13081 specifically see this comment
• Regression in 1.11.5/1.20.1 when using ExternalName service with IP address #13076

What this PR does / why we need it:

We need this to stabilize the behavior of Ingress backend by a service with type ExternalName across different kubernetes versions and going forward.

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

fixes #13081

How Has This Been Tested?

Adding tests to the Lua part of the code that was effected covering previously untested behavior and the specific exception from issue #13081

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.

[k8s-ci-robot]

Hi @neerfri. 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.

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

I understand the commands that are listed here.

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.

[netlify]

✅ Deploy Preview for kubernetes-ingress-nginx ready!

Name	Link
🔨 Latest commit	ee9b312
🔍 Latest deploy log	https://app.netlify.com/projects/kubernetes-ingress-nginx/deploys/6835db2f896d980008f1dad9
😎 Deploy Preview	https://deploy-preview-13154--kubernetes-ingress-nginx.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[Gacko]

/ok-to-test

[Gacko]

/triage accepted
/kind bug
/priority important-soon

[strongjz]

@neerfri Can you look into why the lua test fails?

[Gacko]

Tests are currently failing because we are currently in the progress of releasing a NGINX base image v2.1.1. Don't worry about that.

[neerfri]

@Gacko Thanks for the notice. I think mine is failing due to problems in code.
I've been trying to get to the bottom of this for a long time already but I'm unable to pinpoint the exact reason.
I have now resorted to "printf debugging" 😂

[neerfri]

@Gacko @strongjz
Printf debugging proved extremely useful, as always 😂
Lua tests are now passing
I've merged the main branch
I believe this is ready to be reviewed and merged

Have a lovely day ✨

[Gacko]

Hey! Thank you very much! Looks good (and simple) so far. As soon as @strongjz approves my image promotion PRs, we can go on and merge this.

[Gacko]

/triage accepted
/kind bug
/priority important-soon
/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

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.

[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

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.

[Gacko]

I triggered the tests as the NGINX base image got promoted now. 🙂

[Gacko]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [Gacko]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-infra-cherrypick-robot]

@Gacko: new pull request created: #13429

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: #13430

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.