This operator coordinates the rollout of pods between different StatefulSets within a specific namespace and can be used to manage multi-AZ deployments where pods running in each AZ are managed by a dedicated StatefulSet.

The operator coordinates the rollout of pods belonging to StatefulSets with the rollout-group label and updates strategy set to OnDelete. The label value should identify the group of StatefulSets to which the StatefulSet belongs to.

For example, given the following StatefulSets in a namespace:

• ingester-zone-a with rollout-group: ingester
• ingester-zone-b with rollout-group: ingester
• compactor-zone-a with rollout-group: compactor
• compactor-zone-b with rollout-group: compactor

The operator independently coordinates the rollout of pods of each group:

• Rollout group: ingester
  • ingester-zone-a
  • ingester-zone-b
• Rollout group: compactor
  • compactor-zone-a
  • compactor-zone-b

For each rollout group, the operator guarantees:

1. Pods in 2 different StatefulSets are not rolled out at the same time
2. Pods in a StatefulSet are rolled out if and only if all pods in all other StatefulSets of the same group are Ready (otherwise it will start or continue the rollout once this check is satisfied)
3. Pods are rolled out if and only if all StatefulSets in the same group have OnDelete update strategy (otherwise the operator will skip the group and log an error)
4. The maximum number of not-Ready pods in a StatefulSet doesn't exceed the value configured in the rollout-max-unavailable annotation (if not set, it defaults to 1). Values:

• <= 0: invalid (will default to 1 and log a warning)
• 1: pods are rolled out sequentially
• > 1: pods are rolled out parallelly (honoring the configured number of max unavailable pods)

The operator runs an HTTP server listening on port -server.port=8001 exposing the following endpoints.

Readiness probe endpoint.

Prometheus metrics endpoint.

When running the rollout-operator as a pod, it needs a Role with at least the following privileges:

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
rules:
- apiGroups:
  - ""
  resources:
  - pods
  verbs:
  - list
  - get
  - watch
  - delete
- apiGroups:
  - apps
  resources:
  - statefulsets
  verbs:
  - list
  - get
  - watch
- apiGroups:
  - apps
  resources:
  - statefulsets/status
  verbs:
  - update