Agent skill

deploying-postgres-k8s

Deploys PostgreSQL on Kubernetes using the CloudNativePG operator with automated failover. Use when setting up PostgreSQL for production workloads, high availability, or local K8s development. Covers operator installation, cluster creation, connection secrets, and backup configuration. NOT when using managed Postgres (Neon, RDS, Cloud SQL) or simple Docker containers.

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SKILL.md

Deploying PostgreSQL on Kubernetes

Deploy production-ready PostgreSQL clusters using CloudNativePG operator (v1.28+) with automated failover.

Quick Start

bash
# 1. Install CloudNativePG operator
kubectl apply --server-side -f \
  https://raw.githubusercontent.com/cloudnative-pg/cloudnative-pg/release-1.28/releases/cnpg-1.28.0.yaml

# 2. Wait for operator
kubectl rollout status deployment -n cnpg-system cnpg-controller-manager

# 3. Deploy PostgreSQL cluster
kubectl apply -f - <<EOF
apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: pg-cluster
spec:
  instances: 3
  storage:
    size: 10Gi
EOF

# 4. Wait for cluster
kubectl wait cluster/pg-cluster --for=condition=Ready --timeout=300s

Operator Installation

Direct Manifest (Recommended)

bash
kubectl apply --server-side -f \
  https://raw.githubusercontent.com/cloudnative-pg/cloudnative-pg/release-1.28/releases/cnpg-1.28.0.yaml

# Verify
kubectl rollout status deployment -n cnpg-system cnpg-controller-manager
kubectl get pods -n cnpg-system

Helm Installation

bash
helm repo add cnpg https://cloudnative-pg.github.io/charts
helm repo update

helm upgrade --install cnpg \
  --namespace cnpg-system \
  --create-namespace \
  cnpg/cloudnative-pg

Namespace-Scoped (Enhanced Security)

bash
helm upgrade --install cnpg \
  --namespace cnpg-system \
  --create-namespace \
  --set config.clusterWide=false \
  cnpg/cloudnative-pg

Cluster Configurations

Development (Single Instance)

yaml
apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: pg-dev
spec:
  instances: 1
  imageName: ghcr.io/cloudnative-pg/postgresql:17.2
  primaryUpdateStrategy: unsupervised
  storage:
    size: 5Gi
  postgresql:
    parameters:
      max_connections: "100"
      shared_buffers: "256MB"

Production (HA with 3 Replicas)

yaml
apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: pg-production
spec:
  instances: 3
  imageName: ghcr.io/cloudnative-pg/postgresql:17.2
  primaryUpdateStrategy: unsupervised

  storage:
    storageClass: standard
    size: 100Gi

  resources:
    requests:
      memory: "2Gi"
      cpu: "1"
    limits:
      memory: "4Gi"
      cpu: "2"

  postgresql:
    parameters:
      max_connections: "200"
      shared_buffers: "1GB"
      effective_cache_size: "3GB"
      maintenance_work_mem: "256MB"
      checkpoint_completion_target: "0.9"
      wal_buffers: "16MB"
      default_statistics_target: "100"
      random_page_cost: "1.1"
      effective_io_concurrency: "200"

  affinity:
    podAntiAffinityType: required  # Spread across nodes

  monitoring:
    enablePodMonitor: true

With Bootstrap Database

yaml
apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: pg-cluster
spec:
  instances: 3
  storage:
    size: 10Gi

  bootstrap:
    initdb:
      database: learnflow
      owner: app_user
      secret:
        name: app-user-secret

Create the secret first:

bash
kubectl create secret generic app-user-secret \
  --from-literal=username=app_user \
  --from-literal=password=$(openssl rand -hex 16)

Connection Secrets

CloudNativePG automatically creates connection secrets:

Secret Contents
pg-cluster-app App credentials (recommended)
pg-cluster-superuser Superuser credentials

Get Connection String

bash
# Get app credentials
kubectl get secret pg-cluster-app -o jsonpath='{.data.uri}' | base64 -d

# Get superuser credentials (admin tasks only)
kubectl get secret pg-cluster-superuser -o jsonpath='{.data.uri}' | base64 -d

Use in Deployment

yaml
env:
  - name: DATABASE_URL
    valueFrom:
      secretKeyRef:
        name: pg-cluster-app
        key: uri

Service Endpoints

Service Port Use
pg-cluster-rw 5432 Read-Write (primary)
pg-cluster-ro 5432 Read-Only (replicas)
pg-cluster-r 5432 Any instance

Connect from Another Namespace

yaml
env:
  - name: DATABASE_URL
    value: "postgresql://app_user:password@pg-cluster-rw.default.svc.cluster.local:5432/learnflow"

Database Operations

Connect with psql

bash
# Using kubectl cnpg plugin (recommended)
kubectl cnpg psql pg-cluster -- -c "SELECT version();"

# Or directly
kubectl exec -it pg-cluster-1 -- psql -U postgres

Create Database and User

bash
kubectl exec -it pg-cluster-1 -- psql -U postgres <<EOF
CREATE DATABASE myapp;
CREATE USER myapp_user WITH ENCRYPTED PASSWORD 'secure_password';
GRANT ALL PRIVILEGES ON DATABASE myapp TO myapp_user;
\c myapp
GRANT ALL ON SCHEMA public TO myapp_user;
EOF

Run Migrations

bash
# From local machine
kubectl port-forward svc/pg-cluster-rw 5432:5432 &
DATABASE_URL="postgresql://postgres:password@localhost:5432/learnflow" alembic upgrade head

Backup Configuration

Backup to S3

yaml
apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: pg-cluster
spec:
  instances: 3
  storage:
    size: 10Gi

  backup:
    barmanObjectStore:
      destinationPath: "s3://my-bucket/pg-backups"
      s3Credentials:
        accessKeyId:
          name: s3-creds
          key: ACCESS_KEY_ID
        secretAccessKey:
          name: s3-creds
          key: SECRET_ACCESS_KEY
      wal:
        compression: gzip
      data:
        compression: gzip
    retentionPolicy: "30d"

Schedule Backups

yaml
apiVersion: postgresql.cnpg.io/v1
kind: ScheduledBackup
metadata:
  name: pg-backup-daily
spec:
  schedule: "0 0 * * *"  # Daily at midnight
  backupOwnerReference: cluster
  cluster:
    name: pg-cluster

Monitoring

Check Cluster Status

bash
kubectl get cluster pg-cluster
kubectl describe cluster pg-cluster
kubectl get pods -l cnpg.io/cluster=pg-cluster

View Logs

bash
kubectl logs pg-cluster-1 -f
kubectl logs -l cnpg.io/cluster=pg-cluster --all-containers

Prometheus Metrics

With enablePodMonitor: true, metrics available at:

  • cnpg_backends_total - Active connections
  • cnpg_pg_replication_lag_seconds - Replica lag
  • cnpg_pg_database_size_bytes - Database size

Troubleshooting

Cluster Not Ready

bash
kubectl describe cluster pg-cluster
kubectl get pods -l cnpg.io/cluster=pg-cluster
kubectl logs pg-cluster-1

Connection Issues

bash
# Test connectivity
kubectl run pg-client --rm -it --restart=Never \
  --image=postgres:17 -- \
  psql "postgresql://app_user:password@pg-cluster-rw:5432/learnflow" -c "SELECT 1;"

Common Issues

Error Cause Fix
PVC pending No storage class Add storageClass to spec
Connection refused Wrong service name Use cluster-rw for writes
Auth failed Wrong credentials Check secret cluster-app
Replica lag high Heavy writes Scale up, increase resources

Cleanup

bash
# Delete cluster (keeps PVCs by default)
kubectl delete cluster pg-cluster

# Delete PVCs (data loss!)
kubectl delete pvc -l cnpg.io/cluster=pg-cluster

# Remove operator
kubectl delete -f \
  https://raw.githubusercontent.com/cloudnative-pg/cloudnative-pg/release-1.28/releases/cnpg-1.28.0.yaml

Verification

Run: python scripts/verify.py

Related Skills

  • operating-k8s-local - Local Minikube cluster setup
  • scaffolding-fastapi-dapr - FastAPI services with SQLModel
  • deploying-kafka-k8s - Kafka for event-driven architecture

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