Is there an existing issue already for this bug?

• I have searched for an existing issue, and could not find anything. I believe this is a new bug.

I have read the troubleshooting guide

• I have read the troubleshooting guide and I think this is a new bug.

I am running a supported version of CloudNativePG

• I have read the troubleshooting guide and I think this is a new bug.

Contact Details

No response

Version

1.27 (latest patch)

What version of Kubernetes are you using?

1.34

What is your Kubernetes environment?

Self-managed: kind (evaluation)

How did you install the operator?

YAML manifest

What happened?

Problem Description

I am working on this feature
When attempting to create a CloudNativePG cluster with PostgreSQL extensions that have underscores in their names (e.g., pg_ivm), the cluster fails to start with the following error:

Job.batch "cluster-pg-ivm-1-initdb" is invalid: 
[spec.template.spec.volumes[3].name: Invalid value: "pg_ivm": 
a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', 
and must start and end with an alphanumeric character (e.g. 'my-name', or '123-abc', 
regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')]

Root Cause

The issue occurs in two places:

1. CRD Validation Pattern

   • Current pattern: ^[a-z0-9]([-a-z0-9]*[a-z0-9])?$
   • This pattern only allows lowercase letters, numbers, and hyphens
   • PostgreSQL extension names commonly use underscores (e.g., pg_ivm, pg_stat_statements, pg_trgm)

2. Volume Name Generation

   • The operator uses the extension name directly as the Kubernetes volume name
   • Kubernetes volume names must follow RFC 1123 DNS label rules, which do not allow underscores
   • Even if the CRD validation is patched, the volume creation still fails

Reproduction Steps

1. Apply a cluster manifest with an extension containing underscores:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: cluster-pg-ivm
  namespace: cnpg-system
spec:
  imageName: ghcr.io/cloudnative-pg/postgresql:18-minimal-trixie
  instances: 1
  storage:
    size: 1Gi
  postgresql:
    extensions:
    - name: pg_ivm
      image:
        reference: ghcr.io/shusaan/pg_ivm-testing:1.13-18-trixie

2. The cluster fails to create with the volume name validation error

Attempted Workarounds

Patching the CRD directly does not solve the issue:

kubectl patch crd clusters.postgresql.cnpg.io --type=json -p='[{
  "op": "replace",
  "path": "/spec/versions/0/schema/openAPIV3Schema/properties/spec/properties/postgresql/properties/extensions/items/properties/name/pattern",
  "value": "^[a-zA-Z0-9_]([-_a-zA-Z0-9]*[a-zA-Z0-9])?$"
}]'

This allows the CRD validation to pass, but the cluster still fails because the volume name contains underscores.

Cluster resource

Relevant log output

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