Add regex domain filters

[offzale]

In some use cases, you might need a more flexible way of filtering than the current suffix filtering for zones and domains.

I have added a new filter, RegexDomainFilter, which filters domains and zones by using a regular expression, and has precedence over DomainFilter. Its negative counterpart, RegexDomainExclusion, has been added as well since golang regexp package has some limitations and might be necessary in some use cases.

If RegexDomainFilter is not set, external-dns will work as usual filtering by DomainFilter.

[offzale]

/assign @njuettner

[offzale]

@njuettner any thoughts on this?

[fejta-bot]

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[dsexton]

We may have a usecase for this as well. @linki @njuettner is there anything preventing this from being reviewed?

[offzale]

I have tested it and have been using it in production since I made the PR, it is working as designed. Let me know guys if there is anything you are missing or you think it should be done differently @njuettner @linki @Raffo

/remove-lifecycle stale

[Raffo]

@offzale the change looks legit. Can you add a note in the unreleased section of the changelog? https://github.com/kubernetes-sigs/external-dns/blob/master/CHANGELOG.md

[offzale]

@Raffo thanks for the quick review, I have just added the change you mentioned

[seanmalloy]

/kind feature

[dsexton]

@Raffo can we move forward with this change?

[seanmalloy]

/assign

[seanmalloy]

@offzale can you please fix the merge conflicts? I will review after the merge conflicts are fixed. Thanks!

[offzale]

@seanmalloy thanks for offering to review the PR yourself. I have just fixed the merge conflicts

[fejta-bot]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.

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Send feedback to sig-testing, kubernetes/test-infra and/or fejta.
/lifecycle stale

[offzale]

@seanmalloy did you have a chance to have a look at the changes?

[Raffo]

Sorry for the late re-review, I took a look at this code and it looks like there are several things missing for it to be mergeable. Please take a look at my comments, I will give this a short turnaround if you will address them.

[offzale]

Hi @Raffo, Thanks for the review! I have just committed new changes addressing your comments above. Let me know if you find anything missing.

[Raffo]

@offzale Sorry for the hassle, we removed CHANGELOG.md because it was creating more problems than anything, can you drop your change? I will re-review this after that.

[offzale]

@Raffo thanks for the shout, I have just dropped the change so the MR has no conflicts

[offzale]

/remove-lifecycle stale

[Raffo]

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: offzale, Raffo

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[yogeek]

Hi @offzale ! Thanks for this feature, very useful 👍
Is there any documentation update related to this please ?

[rafalkasa]

Hi @offzale !

I have two kubernetes one test and other production and I would like use your regex filters to filter ingress domains based on it:

Test configuration

      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:v0.8.0
        args:
        - --source=service
        - --source=ingress
        - --domain-filter=example.com
        - --regex-domain-filter=^(.*?(-test.example.com\b)[^$]*)$
        - --provider=azure
        - --azure-resource-group=some-group

Prod configuration

      containers:
      - name: external-dns
        image: k8s.gcr.io/external-dns/external-dns:v0.8.0
        args:
        - --source=service
        - --source=ingress
        - --domain-filter=example.com
        - --regex-domain-exclusion=^(.*?(-test.example.com\b)[^$]*)$
        - --provider=azure
        - --azure-resource-group=some-group

Unfortunately the production external-dns configuration is automatically deleting what was registered by the test external-dns.
This look like that:
- --regex-domain-exclusion=^(.*?(-test.example.com\b)[^$]*)$ not working or working improperly

[rafalkasa]

Correct Prod configuration should be and now everything is working:

  containers:
  - name: external-dns
    image: k8s.gcr.io/external-dns/external-dns:v0.8.0
    args:
    - --source=service
    - --source=ingress
    - --domain-filter=example.com
    - --regex-domain-filter=^(.*?(.example.com\b)[^$]*)$
    - --regex-domain-exclusion=^(.*?(-test.example.com\b)[^$]*)$
    - --provider=azure
    - --azure-resource-group=some-group

@offzale thank you for your work is awesome :-)