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Kubernetes service registration

Kubernetes Service Registration tags OpenBao pods with their current status for use with selectors. Service registration is only available when OpenBao is running in High Availability mode.

  • HashiCorp Supported – Kubernetes Service Registration is officially supported by HashiCorp.

Configuration​

service_registration "kubernetes" {
  namespace      = "my-namespace"
  pod_name       = "my-pod-name"
}

Alternatively, the namespace and pod name can be set through the following environment variables:

  • BAO_K8S_NAMESPACE
  • BAO_K8S_POD_NAME

This allows you to set these parameters using the Downward API.

If using only environment variables, the service registration stanza declaring you're using Kubernetes must still exist to indicate your intentions:

service_registration "kubernetes" {}

For service registration to succeed, OpenBao must be able to apply labels to pods in Kubernetes. The following RBAC rules are required to allow the service account associated with the OpenBao pods to update its own pod specification:

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: mynamespace
  name: openbao-service-account
rules:
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get", "update", "patch"]

Examples​

Once properly configured, enabling service registration will cause Kubernetes pods to come up with the following labels:

apiVersion: v1
kind: Pod
metadata:
  name: openbao
  labels:
    openbao-active: "false"
    openbao-initialized: "true"
    openbao-perf-standby: "false"
    openbao-sealed: "false"
    openbao-version: 2.0.1

After shutdowns, OpenBao pods will bear the following labels:

apiVersion: v1
kind: Pod
metadata:
  name: openbao
  labels:
    openbao-active: "false"
    openbao-initialized: "false"
    openbao-perf-standby: "false"
    openbao-sealed: "true"
    openbao-version: 2.0.1

Label definitions​

  • openbao-active (string: "true"/"false") – openbao-active is updated dynamically each time OpenBao's active status changes. True indicates that this OpenBao pod is currently the leader. False indicates that this OpenBao pod is currently a standby.
  • openbao-initialized (string: "true"/"false") – openbao-initialized is updated dynamically each time OpenBao's initialization status changes. True indicates that OpenBao is currently initialized. False indicates the OpenBao is currently uninitialized.
  • openbao-sealed (string: "true"/"false") – openbao-sealed is updated dynamically each time OpenBao's sealed/unsealed status changes. True indicates that OpenBao is currently sealed. False indicates that OpenBao is currently unsealed.
  • openbao-version (string: "2.0.1") – OpenBao version is a string that will not change during a pod's lifecycle.

Working with OpenBao's service discovery labels​

Example service​

With labels applied to the pod, services can be created using selectors to filter pods with specific OpenBao HA roles, effectively allowing direct communication with subsets of OpenBao pods. Note the openbao-active: "true" line below.

apiVersion: v1
kind: Service
metadata:
  labels:
    app.kubernetes.io/instance: openbao
    app.kubernetes.io/name: openbao
    helm.sh/chart: openbao-0.1.2
  name: openbao-active-us-east
  namespace: default
spec:
  clusterIP: 10.7.254.51
  ports:
  - name: http
    port: 8200
    protocol: TCP
    targetPort: 8200
  - name: internal
    port: 8201
    protocol: TCP
    targetPort: 8201
  publishNotReadyAddresses: false
  selector:
    app.kubernetes.io/instance: openbao
    app.kubernetes.io/name: openbao
    component: server
    openbao-active: "true"
  type: ClusterIP

Also, by setting publishNotReadyAddresses: false above, pods that have failed will be removed from the service pool.

With this active service in place, we now have a dedicated endpoint that will always reach the active node.

Example upgrades​

In conjunction with the pod labels and the OnDelete upgrade strategy, upgrades are much easier to orchestrate:

$ helm upgrade openbao --set='server.image.tag=1.14.0'

$ kubectl delete pod --selector=openbao-active=false \
    --selector=openbao-version=2.0.1

$ kubectl delete pod --selector=openbao-active=true \
    --selector=openbao-version=2.0.1

When deleting an instance of a pod, the Statefulset defining the desired state of the cluster will reschedule the deleted pods with the newest image.