Kubernetes

This tutorial connects Sablier to Kubernetes. You will select the Kubernetes provider, grant Sablier the roles it needs to use the Kubernetes API, register a Deployment so Sablier can scale it, and confirm Sablier knows when the Deployment is ready. Sablier assumes that it is deployed within the Kubernetes cluster to use the Kubernetes API internally.

Select the Kubernetes provider

Set the provider.name property to kubernetes.

provider:
  name: kubernetes

sablier start --provider.name=kubernetes

SABLIER_PROVIDER_NAME=kubernetes

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: sablier
rules:
  - apiGroups:
      - apps
      - ""
    resources:
      - deployments
      - statefulsets
    verbs:
      - get     # Retrieve info about specific dep
      - list    # Events
      - watch   # Events
  - apiGroups:
      - apps
      - ""
    resources:
      - deployments/scale
      - statefulsets/scale
    verbs:
      - patch   # Scale up and down
      - update  # Scale up and down
      - get     # Retrieve info about specific dep
      - list    # Events
      - watch   # Events
  # Only required if you manage CloudNativePG Clusters (see below).
  - apiGroups:
      - postgresql.cnpg.io
    resources:
      - clusters
    verbs:
      - get     # Retrieve info about a specific cluster
      - list    # Discovery and events
      - watch   # Events
      - patch   # Toggle the hibernation annotation
  # Only required if you manage OT-CONTAINER-KIT Redis instances (see below).
  - apiGroups:
      - redis.redis.opstreelabs.in
    resources:
      - redis
    verbs:
      - get     # Resolve the Redis CR owner of a StatefulSet
      - patch   # Toggle the skip-reconcile annotation

Register a Deployment

For Sablier to work, it needs to know which deployments to scale up and down. Register a Deployment by opting in with labels:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: whoami
  labels:
    app: whoami
    sablier.enable: "true"
    sablier.group: mygroup
spec:
  selector:
    matchLabels:
      app: whoami
  template:
    metadata:
      labels:
        app: whoami
    spec:
      containers:
      - name: whoami
        image: acouvreur/whoami:v1.10.2

Confirm when the deployment is ready

Sablier checks for the deployment replicas. As soon as the current replicas matches the wanted replicas, then the deployment is considered ready.

Configure with labels or annotations

On Kubernetes, sablier.* keys can be set either as a label or as an annotation, with one exception: sablier.enable must always be a label (see the note below). This applies to Deployments, StatefulSets, CloudNativePG Clusters and OT-CONTAINER-KIT Redis instances.

Annotations are useful because Kubernetes label values are restricted (max 63 characters, only [A-Za-z0-9._-], no commas or colons). Some Sablier values cannot be expressed as labels and must use annotations, for example:

• sablier.group with multiple comma-separated groups (e.g. team-a,team-b)
• sablier.running-hours (e.g. 09:00-18:00), where the colon is invalid in a label value
• sablier.running-days (e.g. Mon,Tue,Wed,Thu,Fri)

When the same key is present as both a label and an annotation, the annotation takes precedence.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: whoami
  labels:
    app: whoami
    sablier.enable: "true"       # must be a label
  annotations:
    sablier.group: "team-a,team-b"          # comma is invalid as a label value
    sablier.running-hours: "09:00-18:00"    # colon is invalid as a label value
    sablier.running-days: "Mon,Tue,Wed,Thu,Fri"
spec:
  # ...existing spec...

Register CloudNativePG Clusters

Sablier can also start and stop CloudNativePG Cluster resources. Instead of scaling a replica count, Sablier toggles CloudNativePG’s declarative hibernation annotation:

• Stop sets cnpg.io/hibernation: "on", and the operator scales the cluster down and removes its workload while keeping the PVCs.
• Start sets cnpg.io/hibernation: "off", and the operator resumes the cluster.

Opt-in with the same labels used for deployments and statefulsets:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: opencell-db
  labels:
    sablier.enable: "true"
    sablier.group: opencell
spec:
  instances: 3
  storage:
    size: 1Gi

This makes it possible to put an application, its Keycloak and its database in a single sablier.group, so that a single request wakes up the whole stack and inactivity hibernates all of it.

Cluster readiness

A CloudNativePG Cluster is considered:

• stopped when the cnpg.io/hibernation annotation is "on";
• ready when status.readyInstances is greater than or equal to spec.instances;
• starting otherwise.

Register OT-CONTAINER-KIT Redis instances

Sablier can scale to zero StatefulSets managed by the OT-CONTAINER-KIT redis-operator. The operator continuously reconciles its StatefulSets back to the desired replica count, so a plain scale-to-zero is immediately undone. Sablier works around this by toggling the operator’s own pause mechanism:

• Stop sets redis.opstreelabs.in/skip-reconcile: "true" on the Redis CR, then scales the StatefulSet to 0.
• Start scales the StatefulSet back to 1, then removes the annotation so the operator resumes normal reconciliation.

If the scale fails, the annotation is cleared immediately so the operator is never left paused with pods still running.

Opt-in by adding the standard Sablier labels to the Redis CR. The operator propagates them to the StatefulSet it manages, so no extra labelling is needed:

apiVersion: redis.redis.opstreelabs.in/v1beta2
kind: Redis
metadata:
  name: myapp-redis
  labels:
    sablier.enable: "true"
    sablier.group: myapp
spec:
  kubernetesConfig:
    image: quay.io/opstree/redis:v7.0.12

This makes it straightforward to group a Redis instance with the rest of an application stack so that a single request wakes everything up and inactivity shuts it all down together.