PostgreSQL FAQs

1. Use ETCD as Patroni DCS

KubeBlocks PostgreSQL uses the Kubernetes API itself as DCS (Distributed Config Store) by default. But when the control plane is under extreme high load, it may lead to unexpected demotion of the primary replica. And it's recommended to use ETCD as DCS in such extreme cases.

apiVersion: apps.kubeblocks.io/v1
kind: Cluster
metadata:
  name: pg-cluster-etcd
  namespace: demo
spec:
  terminationPolicy: Delete
  clusterDef: postgresql
  topology: replication
  componentSpecs:
    - name: postgresql
      serviceVersion: "16.4.0"
      env:
      - name: DCS_ENABLE_KUBERNETES_API  # unset this env if you use zookeeper or etcd, default to empty
      - name: ETCD3_HOST
        value: 'etcd-cluster-etcd-headless.demo.svc.cluster.local:2379' # where is your etcd?
      # - name: ZOOKEEPER_HOSTS
      #   value: 'myzk-zookeeper-0.myzk-zookeeper-headless.demo.svc.cluster.local:2181' # where is your zookeeper?
      replicas: 2
      resources:
        limits:
          cpu: "0.5"
          memory: "0.5Gi"
        requests:
          cpu: "0.5"
          memory: "0.5Gi"
      volumeClaimTemplates:
        - name: data
          spec:
            storageClassName: ""
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi

The key fields are:

• DCS_ENABLE_KUBERNETES_API: Unset this env to use ETCD or ZooKeeper as DCS
• ETCD3_HOST: The host of ETCD cluster

You can also use ZooKeeper as DCS by unsetting DCS_ENABLE_KUBERNETES_API and setting ZOOKEEPER_HOSTS to the host of ZooKeeper cluster.

KubeBlocks has ETCD and ZooKeeper Addons in the kubeblocks-addons repository. You can refer to the following links for more details.

• https://github.com/apecloud/kubeblocks-addons/tree/main/examples/etcd
• https://github.com/apecloud/kubeblocks-addons/tree/main/examples/zookeeper

You can shell into one of the etcd container to view the etcd data, and view the etcd data with etcdctl.

etcdctl get /service --prefix