README

A Helm chart for a PostgreSQL cluster with a PgPool frontend.

1.Prerequisites

1.1. Build and publish PgPool image

Build and tag the image for PgPool. Say, for example, we tag the image as registry.internal:5000/pgpool:4:

docker build ./pgpool/redhat/ -f pgpool/redhat/Dockerfile -t registry.internal:5000/pgpool:4

Push the image to the respective registry:

docker push registry.internal:5000/pgpool:4

1.2. Configure the Helm chart

Create a YAML file, say values-local.yml, to provide or override values from values.yml.

For password-related secrets, if not mentioned otherwise, we expect a single item named password. This can be created for example:

kubectl create secret generic some-postgres-password --from-file=password=secrets/postgres-password

All values are documented inside values.yml.

1.3. Provide persistent volumes (PVs)

A set of PVs must be created to bind to PVCs from master/standby statefulsets.

There are 2 ways to achieve a predictable binding of PVCs to PVs: (a) defining a claimRef in a PV (which is created in advance) to match the expected PVC name (b) define selective matchLabels for PVs to match labels requested by generated PVCs

In any case, the storage class for a data/archive directory can be specified in values.yaml (default is local-1 for data and nfs-1 for archive).

1.3.a. Provide a PV using a claimRef

The expected names for PVCs are deterministic (in the case of statefulsets), so we can prepare PVs that reference this expected PVC name (using claimRef). Note that selector labels (if requested at the PVC side) will be ignored if a claimRef is specified. On the contrary, requested storage classes must be respected.

The PVC names are:

• data-{{fullname}}-master-0: data directory for master (a single instance in the statefulset)
• data-{{fullname}}-standby-{{ordinal}}: data directory for a standby instance (ordinal comes from the statefulset)
• archive-{{fullame}}: archive directory where each server (master and standbys) stores WAL segments in a separate subdirectory (named as $(POD_NAME))

An example for providing a PV for master data directory, for a Helm release named postgres-c1:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: postgres-c1-data-ac30a47d44f2
  labels:
    app.kubernetes.io/name: postgresql-cluster
    app.kubernetes.io/instance: postgres-c1
spec:
  storageClassName: local-1
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 1Gi
  volumeMode: Filesystem
  persistentVolumeReclaimPolicy: Retain
  claimRef:
    namespace: default
    name: data-postgres-c1-master-0
  local:
    path: /data/postgres-c1/data-ac30a47d44f2
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - minikube

1.3.b. Provide a PV matching labels

The labels requested for the PVC for the data directory for the master (and similar for standby):

app.kubernetes.io/name: postgresql-cluster
app.kubernetes.io/instance: {{releaseName}}
postgresql-cluster.opertusmundi.github.io/master: ""

The labels requested for the PVC for the archive directory:

app.kubernetes.io/name: postgresql-cluster
app.kubernetes.io/instance: {{releaseName}}