Charmed PostgreSQL K8s

Charm types “legacy” vs “modern”

There are two types of charms stored under the same charm name postgresql(-k8s):

1. Reactive charm in the channel latest/stable (called legacy)
2. Ops-based charm in the channel 14/stable (called modern)

The legacy charm provided endpoints db and db-admin (for the interface pgsql). The modern charm provides old endpoints as well + new endpoint database (for the interface postgresql_client). Read more detail about the available endpoints/interfaces for VM and K8s charms.

Note: Please choose one endpoint to use. No need to relate all of them simultaneously!

The default track “latest” vs “14”

The default track has been switched from the latest to 14 for both VM and K8s PostgreSQL charms. It is to ensure all new deployments use a modern codebase. We strongly advise against using the latest track due to its implicit nature. In doing so, a future charm upgrade may result in a PostgreSQL version incompatible with an integrated application. Track 14 guarantees PostgreSQL 14 deployment only. The track latest will be closed after all applications migrated from Reactive to Ops-based charm.

How to migrate from “legacy” to “modern” charm

The “modern” charm provides temporary support for the legacy interfaces:

• quick try: relate the current application with new charm using endpoint db (set the channel to 14/stable). No extra changes necessary:

  postgresql:
    charm: postgresql
    channel: 14/stable

• proper migration: migrate the application to the new interface “postgresql_client”. The application will connect PostgreSQL using “data_interfaces” library from “data-platform-libs” via endpoint database.

Warning: NO in-place upgrades possible! Reactive charm cannot be upgraded to Operator-framework-based one. To move DB data, the second/modern DB application must be launched nearby and data should be copied from “legacy” application to the “modern” one. Canonical Data Platform team is preparing copy&paste guide right now. Please contact us if you need migration instructions.

How to deploy old “legacy” postgresql charm

Deploy the charm using the channel latest/stable:

  postgresql:
    charm: postgresql
    channel: latest/stable

Note: remove Charm store prefix cs: from the bundle. Otherwise the modern charm will be chosen by Juju (due to the default track pointing to 14/stable and not latest/stable). The common error message is: cannot deploy application "postgresql": unknown option "...".

Config options and Extensions support by modern charm

The modern charm does NOT support PostgreSQL config options and Extensions right now. Please contact us with a list of required config options and extensions (and/or legacy charm config options).

Supported PostgreSQL versions by modern charm

At the moment, both K8s and VM modern charms support PostgreSQL 14 (based on Jammy/22.04 series) only. Please contact us if you need different versions/series.