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k8s deployer: WaitForDeploymentAvailable errors on a 0-replica Deployment (keda scale-to-zero redeploy)

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Los mantenedores suelen responder en 1 día

@Elvand-Lie ya está trabajando en esto.

Desde el 11/10/2026.

  • #4075 de @Elvand-Lie — abierto

Evaluación

Dificultad
3/5
Tiempo estimado
1-2 días
Aptitud para principiantes
72/100
Tipo de issue
Error
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
go, kubernetes
Área
infrastructure

Línea de trabajo

Start by reading WaitForDeploymentAvailable and checkIfDeploymentIsAvailable in pkg/k8s/wait.go, then compare how deployments are applied in pkg/k8s/deployer.go. Add coverage for the zero-replica case and verify the existing wait behavior remains intact; a KEDA-backed redeploy can provide the integration repro if needed.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Summary

WaitForDeploymentAvailable (pkg/k8s/wait.go) can fail a redeploy with
could not find current pod-template-hash for deployment <name> when the live
Deployment has 0 desired replicas. This is reachable today via the keda
(HTTP-scaler) deployer, whose ScaledObject scales idle functions down to zero.

Note: this is reasoned from the code, not yet reproduced (it's a timing race).
Filing so the analysis is tracked; repro TBD.

Details

WaitForDeploymentAvailable re-fetches the live Deployment on every poll tick:

deployment, err := clientset.AppsV1().Deployments(namespace).Get(ctx, deploymentName, metav1.GetOptions{})
...
return checkIfDeploymentIsAvailable(ctx, clientset, deployment)

checkIfDeploymentIsAvailable finds the active ReplicaSet by looking for one with
*rs.Spec.Replicas > 0. A Deployment sitting at 0 desired replicas has no such
ReplicaSet, so currentPodTemplateHash stays empty and the function returns an error
(pkg/k8s/wait.go):

if currentPodTemplateHash == "" {
    return false, fmt.Errorf("could not find current pod-template-hash for deployment %s", deployment.Name)
}

The func deployer itself always applies replicas >= 1 (pkg/k8s/deployer.go), so
it never creates a 0-replica Deployment. But because the wait inspects live state,
reachability is governed by what KEDA does during the wait, not by what func wrote:

  1. An idle keda-HTTP function has been scaled to 0 replicas by KEDA.
  2. User redeploys. func applies the Deployment with replicas: 1, then starts polling.
  3. If the KEDA controller reasserts 0 replicas on the live Deployment before the poll
    observes it as ready, the live fetch returns spec.replicas == 0, and the wait
    returns the pod-template-hash error — failing the redeploy.
Suggested fix

Short-circuit when there is nothing to wait for:

desiredReplicas := *deployment.Spec.Replicas
if desiredReplicas == 0 {
    return true, nil // no replicas desired; nothing to wait for
}

This also unblocks any future spec-level scale-to-zero on the raw/keda Deployment.

Notes
  • Reasoned from code; not reproduced. A repro needs a cluster with KEDA and an idle,
    scaled-to-zero HTTP function being redeployed.
  • Fix is small and self-contained but likely wants a repro or unit test first, hence
    filing as an issue rather than an immediate PR.
Lenguaje dominante
Go
Estrellas
366
Forks
226
Merge medio
2 d 17 h
PR fusionados (30 d)
21

Preparar el entorno

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

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