feat(api): set trafficDistribution on the client Service by kvaps · Pull Request #376 · cozystack/etcd-operator

Andrei Kvapil (kvaps) · 2026-10-14T17:04:36Z

What

Adds an optional spec.clientService.trafficDistribution to EtcdCluster. When set, the operator writes it to spec.trafficDistribution of the <cluster>-client Service on create and reconciles drift back to it. Allowed values mirror the core Service API: PreferClose, PreferSameZone, PreferSameNode, validated by an enum on the CRD.

Why

Clusters stretched across zones (e.g. two sites plus a witness) want clients to prefer an etcd member in their own zone. The client Service has a selector, so with trafficDistribution: PreferClose the EndpointSlice controller writes zone hints and proxies that honour them (kube-proxy, Cilium) keep traffic zone-local. Today this can only be done by patching the Service by hand, which survives reconcile but is lost when the Service is recreated.

Behaviour

Unset (no clientService, or no trafficDistribution in it) means no change from today: the operator does not touch the field, so a value set on the Service by hand is preserved.
Only the client Service is affected; the headless Service never gets a traffic distribution.
The setting is not latched through status.observed — the Service carries no consensus state, so a change applies on the next reconcile.
clientService is a struct so further client-Service settings can land next to it.

Compatibility

PreferClose needs Kubernetes 1.31+ (GA in 1.33); PreferSameZone / PreferSameNode need 1.34+. Documented on the field and in docs/concepts.md.

Testing

Controller tests: create, drift reconciled back to the spec, unset field leaves a hand-set value alone, headless Service untouched.
envtest: CRD enum accepts the three values and rejects others; the envtest apiserver persists trafficDistribution on a Service.
make test passes; make generate manifests produces no drift.

Summary by CodeRabbit

New Features
- Added optional traffic distribution settings for the client Service: PreferClose, PreferSameZone, and PreferSameNode.
- Configured values are applied and reconciled on the next update. When unset, existing Service settings are preserved; the headless Service is unaffected.
Documentation
- Added guidance on client Service configuration and its behavior.

Clusters stretched across zones want clients of the <cluster>-client Service to prefer a member in their own zone. Add an optional clientService block with a trafficDistribution field whose allowed values mirror the core Service API. Unset leaves today's behaviour. Assisted-by: LLM Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

Set spec.trafficDistribution on <cluster>-client from spec.clientService and reconcile drift back to it. The field is only owned when the EtcdCluster sets it, so a value patched onto the Service by hand survives when the spec leaves it unset. The headless Service is never touched. Assisted-by: LLM Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

Controller tests for create, drift back to the spec, an unset field leaving a hand-set value alone, and the headless Service never being touched. envtest cases for the enum on spec.clientService and for the apiserver persisting the field on a Service. Assisted-by: LLM Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

Document the client Service, which fields the operator owns on it, and the new trafficDistribution setting for zone-local clients in clusters stretched across zones, including apiserver version requirements. Assisted-by: LLM Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

coderabbitai · 2026-10-14T17:04:48Z

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📥 Commits

Reviewing files that changed from the base of the PR and between e6c1314 and 7da403d.

📒 Files selected for processing: 8

README.md
api/v1alpha2/client_service_envtest_test.go
api/v1alpha2/etcdcluster_types.go
api/v1alpha2/zz_generated.deepcopy.go
charts/etcd-operator/crd-bases/etcd-operator.cozystack.io_etcdclusters.yaml
controllers/client_service_test.go
controllers/etcdcluster_controller.go
docs/concepts.md

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📝 Walkthrough

The API adds optional traffic distribution settings for the client Service. The controller applies configured values and reconciles drift. When the setting is absent, the controller preserves the Service’s existing value. The headless Service is not changed by this configuration.

Changes: Client Service traffic distribution

Layer / File(s)	Summary
Client Service configuration contract `api/v1alpha2/etcdcluster_types.go`, `api/v1alpha2/zz_generated.deepcopy.go`, `charts/etcd-operator/crd-bases/etcd-operator.cozystack.io_etcdclusters.yaml`, `api/v1alpha2/client_service_envtest_test.go`	Adds the optional `clientService.trafficDistribution` field with three allowed values, deep-copy support, the CRD schema, and API-server tests for accepted values and persistence.
Client Service reconciliation `controllers/etcdcluster_controller.go`, `controllers/client_service_test.go`, `docs/concepts.md`, `README.md`	The controller applies configured values to the client Service and preserves existing values when configuration is absent. Tests cover creation, drift, and headless Service behavior. Documentation describes the option and its Kubernetes version requirements.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Merge Risk: ⚪ Minimal · up to 7da40

The client Service configuration appears ready to merge after normal checks; no actionable issue is established.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 72.73% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 5 files. (3 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: adding support for setting trafficDistribution on the client Service.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 72.73% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 5 files. (3 skipped: 3 unsupported.)

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Kirill Ilin (sircthulhu)

LGTM, two minor comments inline.

This reverts commit eccc4fb, removing spec.clientService.trafficDistribution from the EtcdCluster API. The capability returns in the next commit as an annotation on the EtcdCluster, so the API does not change for now. Assisted-By: LLM Signed-off-by: Timofei Larkin <lllamnyp@gmail.com>

…otation The etcd-operator.cozystack.io/client-service-traffic-distribution annotation on an EtcdCluster sets spec.trafficDistribution on the <cluster>-client Service (PreferClose, PreferSameZone or PreferSameNode), so clients of a cluster stretched across zones prefer a nearby member. It stands in for a typed spec field without changing the API for now. The field is written with server-side apply under its own field manager, so removing the annotation clears it unless another manager also set it, and a value someone else set without the annotation is left alone. A value outside that set, one the apiserver rejects (PreferSameZone and PreferSameNode before 1.34) or one it drops (no support before 1.31) is reported as a Warning Event and leaves the field unset; the rest of the reconcile carries on. The headless Service is not touched. Builds on the controller tests and docs of #376 by Andrei Kvapil. Assisted-By: LLM Signed-off-by: Timofei Larkin <lllamnyp@gmail.com>

Andrei Kvapil (kvaps) added 4 commits October 14, 2026 21:57

github-actions Bot added api-change controllers documentation Improvements or additions to documentation feature New feature or request labels Oct 14, 2026

Andrei Kvapil (kvaps) marked this pull request as ready for review October 14, 2026 17:06

Andrei Kvapil (kvaps) requested review from Andrey Kolkov (androndo), Timofei Larkin (lllamnyp) and Kirill Ilin (sircthulhu) as code owners October 14, 2026 17:06

Kirill Ilin (sircthulhu) approved these changes Oct 15, 2026

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Comment thread controllers/etcdcluster_controller.go

Comment thread controllers/etcdcluster_controller.go

Timofei Larkin (lllamnyp) mentioned this pull request Oct 16, 2026

feat(controllers): set client Service trafficDistribution from an annotation #377

Merged

Andrei Kvapil (kvaps) merged commit eccc4fb into main Oct 17, 2026
11 checks passed

Andrei Kvapil (kvaps) deleted the feat/client-service-traffic-distribution branch October 17, 2026 07:16

This was referenced Oct 17, 2026

fix(controllers): keep reconciling when trafficDistribution is unsupported #378

Open

feat(etcd-operator): update to v0.5.7 cozystack/cozystack#4942

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feat(api): set trafficDistribution on the client Service - #376

feat(api): set trafficDistribution on the client Service#376
Andrei Kvapil (kvaps) merged 4 commits into
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feat/client-service-traffic-distribution

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