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feat(provider/google): preserve gcp txt ownership #5855

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TobyTheHutt
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What does it do ?

  • Implements safe “type swap” handling in the Google provider: when a record’s type changes at the same name (e.g., A - CNAME), the provider emits a single dns.Change that deletes the old type first and adds the new type second.
  • Normalizes swap matching by DNS name using a lowercase, trailing-dot key to avoid case and dot variance.
  • Excludes TXT records from swap eligibility to preserve ownership.
  • Preserves the external-dns/owner label by copying it from the deleted record to the newly created record.
  • Refactors ApplyChanges to integrate swaps alongside existing create/update/delete flows, keeping behavior deterministic.
  • Adds unit tests for type-swap scenarios, TXT exclusion, case insensitivity, and multi-delete consumption behavior.
  • Minor cleanups: preallocations for remaining lists and strings import for key normalization.

Motivation

Fixes the Google Cloud DNS limitation where ExternalDNS could not change a record’s type at the same name without a manual delete.
It's issuing a delete-then-add, therefore atomically resolving API conflicts.

More

  • Yes, this PR title follows Conventional Commits
  • Yes, I added unit tests
  • Yes, I updated end user documentation accordingly

@TobyTheHutt
fix(provider/gcp): bundle record-type swap changes
6e69697 
The change teaches the Google provider to bundle record-type swaps into
a single Cloud DNS change set. It also carries the ownership forward.

* Add new `extractTypeSwaps` helper to pair create/delete endpoints by
  name
* Modify `extractTypeSwaps` to skip TXT records
* Modify `extractTypeSwaps` to copy owner label of the prior RRset onto
  the new record before both ends of the swap are appended to the change
* Modify `ApplyChanges` to receive the new `extractTypeSwaps` helper's
  result for one astomic delete+add per type change
* Add `TestGoogleApplyChangesTypeSwap` to set up A to CNAME transition
* Add tests
  * Assert helper finds a swap
  * Verify that zone holds the CNAME
  * Verify that create endpoint retains original owner label

Signed-off-by: Tobias Harnickell <[email protected]>
@TobyTheHutt
feat(providers/google): Preserve swap owner label
3887b0e 
* Maintain TXT ownership by skipping TXT in type swaps
* Carry owner label forward when swapping record types
* Add tests for swap logic
* Refactor swap extraction for clarity

Signed-off-by: Tobias Harnickell <[email protected]>
@TobyTheHutt
Merge branch 'master' of github.com:TobyTheHutt/external-dns into 433…
ae09a65 
…-preserve-gcp-txt-ownership

Signed-off-by: Tobias Harnickell <[email protected]>
@TobyTheHutt
feat(providers/google): Cleanup Google Provider
0756708 
* Fix `TestGoogleExtractTypeSwapsConsumesSingleDelete` flakiness by
  asserting A-record as the chosen swap source
* Remove unused `matchedType` variable
* Initialize `remainingDeletes` with `make([]*endpoint.Endpoint, 0,
  len(deleteEndpoints))` so "no swaps" mirrors the preallocation used
  for `remainingCreates`
* Document invariants and rationale for `extractTypeSwaps` in code
  comment
* Evaluate buckets deterministically by `typeSwapTypePriority`,
  owner-label preference and stable tie-preakters (leftover deletions
  also deterministically emitted)

Signed-off-by: Tobias Harnickell <[email protected]>
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[APPROVALNOTIFIER] This PR is NOT APPROVED

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@k8s-ci-robot k8s-ci-robot added the provider Issues or PRs related to a provider label Sep 21, 2025
@k8s-ci-robot k8s-ci-robot requested a review from szuecs September 21, 2025 10:26
@k8s-ci-robot k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Sep 21, 2025
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Hi @TobyTheHutt. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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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@k8s-ci-robot k8s-ci-robot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label Sep 21, 2025
@TobyTheHutt
chore(provider/google): Improve readability
a7d3b07 
Split unnecessarily long lines.

Signed-off-by: Tobias Harnickell <[email protected]>
@ivankatliarchuk
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I was working once or twice with GCP, same time AWS and Azure follow same principle record type is immutable.

I'm not too sure how exactly this was resolved, but assuming this is not a case for AWS for example, which means, two records with only different record type, actually two distinct records. So if we have RecordA of type A, changes it's type to type AAAA, we currently have

  • Deleted RecordA (example.com) of type A
  • Created RecordB (example.com) of type AAAA

Few questions;

  1. Is the problem still reproducible?
  2. How exactly this case is managed on AWS or Azure?
  3. Why not to ensure the order of changes - first Create or Delete, then Update? I'm not exactly sure how batching behaves

@ivankatliarchuk
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How this was resolved for AWS #1867

We may need to introduce a principle or best practice for providers add to contributor docs if we could not force a common interface, on what is the correct order of changes to avoid such cases

@ivankatliarchuk
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In cases where a record type changes, resulting in a DELETE + CREATE, retaining the TXT record could be considered an improvement that can be applied across all providers. However, implementing changes to TXT records is not straightforward, as it carries multiple risks and quite often project owners involved with final decision.

@mloiseleur mloiseleur changed the title feat(provider/google): preserve gcp txt ownership (kubernetes-sigs/external-dns#433) feat(provider/google): preserve gcp txt ownership Sep 23, 2025
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external-dns cannot automatically change record type in Google DNS

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@TobyTheHutt @k8s-ci-robot @ivankatliarchuk