# CloudNative Postgres

CloudNative Postgres uses an Operator to watch for new database cluster- and backup- definitions as provided by CRDs.


# Operator

The operator is deployed via helm release


# Cluster & Backups

S3-compatible storage can be used as a live WAL backup. CNPG now uses a [plugin system](https://cloudnative-pg.io/plugin-barman-cloud/docs/intro/).

The backend is Garage, which rejects any region other than `garage`. `objectstore.yaml` sets `AWS_DEFAULT_REGION=garage` through `spec.instanceSidecarConfiguration.env`; the plugin injects that into both the instance sidecar and the `full-recovery` job, so backup, WAL archive, and restore all agree on the region. Without it barman-cloud falls back to the boto3 default of `us-east-1` and every S3 call fails.


# Restore

[k8s-at-home discussion](https://discord.com/channels/673534664354430999/1036720267474509885)

> On versioning: If you end up with an older cloudnative pg backup (i.e. i have a pg14 one) but you're using a newer operator that defaults to newer (i.e. \> 15.1), you wont be able to restore as it will whine about versions. Add an image tag to the cluster spec to deploy a second cluster with a specifically downgraded ver to restore without having to juggle around changing the operator helm etc


# CLI

Install the [kubectl plugin](https://cloudnative-pg.io/documentation/1.18/cnpg-plugin/)


# Updating postgres versions with CNPG

1.  Scale down apps using old cluster
2.  Ensure old cluster is running
3.  Spin up new cluster, pointing `.connectionParameters` to the old cluster
4.  Ensure new cluster has a scheduledBackup pointing to it
5.  Redirect `ext-postgres-operator` to new cluster (edit the cluster fqdn in the secret)
6.  Redirect apps to new cluster
7.  Remove the old cluster (remove before scaling up to make sure apps fully switch over)
8.  Scale up apps 🤞🏼

Refs:

- [The Current State of Major PostgreSQL Upgrades with CloudNativePG \| EDB](https://www.enterprisedb.com/blog/current-state-major-postgresql-upgrades-cloudnativepg-kubernetes)
- [k8s-at-home ref](https://github.com/onedr0p/home-ops/issues/4448#issuecomment-1430440044)

> **Note**
>
> Source: [`kubernetes/apps/datasci/postgres/cloudnative-pg/README.md`](https://github.com/ahgraber/homelab-gitops-k3s/blob/main/kubernetes/apps/datasci/postgres/cloudnative-pg/README.md)