From 8011e9a9e646bb3f7dbfe83348fc453a3ed76762 Mon Sep 17 00:00:00 2001
From: Raphael Torquato <89878688+raphaeltorquat0@users.noreply.github.com>
Date: Sun, 26 Apr 2026 13:52:40 -0300
Subject: [PATCH] feat: allow overriding external-dns hostname annotation

This change allows users to override the external-dns.alpha.kubernetes.io/hostname
annotation by specifying it in serviceAnnotations, masterServiceAnnotations,
or replicaServiceAnnotations in the cluster manifest.

Previously, the operator always overwrote this annotation with the value from
master_dns_name_format or replica_dns_name_format. Now, if the user has
already defined the annotation, the operator will preserve the user's value.

Changes:
- Modified generateServiceAnnotations() to check if annotation exists before setting
- Updated tests to verify user-defined annotations are preserved
- Updated documentation to reflect the new behavior

Closes #2591
---
 docs/administrator.md       |  5 +++--
 pkg/cluster/cluster_test.go | 12 ++++++------
 pkg/cluster/k8sres.go       |  9 +++++----
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/docs/administrator.md b/docs/administrator.md
index e854775ce..e579d1518 100644
--- a/docs/administrator.md
+++ b/docs/administrator.md
@@ -896,8 +896,9 @@ its services:
 
 - `external-dns.alpha.kubernetes.io/hostname` with the value defined by the
   operator configs `master_dns_name_format` and `replica_dns_name_format`.
-  This value can't be overwritten. If any changing in its value is needed, it
-  MUST be done changing the DNS format operator config parameters; and
+  This value can be overwritten by specifying the annotation in
+  `serviceAnnotations`, `masterServiceAnnotations`, or `replicaServiceAnnotations`
+  in the cluster manifest; and
 
 There are multiple options to specify service annotations that will be merged
 with each other and override in the following order (where latter take
diff --git a/pkg/cluster/cluster_test.go b/pkg/cluster/cluster_test.go
index 8046943d4..f08210e7f 100644
--- a/pkg/cluster/cluster_test.go
+++ b/pkg/cluster/cluster_test.go
@@ -767,16 +767,16 @@ func TestServiceAnnotations(t *testing.T) {
 			},
 		},
 		{
-			about:                      "Master with cluster annotations do not override external-dns annotations",
+			about:                      "Master with user-defined external-dns annotation is preserved",
 			role:                       "master",
 			enableMasterLoadBalancerOC: true,
 			enableTeamIdClusterPrefix:  false,
 			operatorAnnotations:        make(map[string]string),
 			serviceAnnotations: map[string]string{
-				"external-dns.alpha.kubernetes.io/hostname": "wrong.external-dns-name.example.com",
+				"external-dns.alpha.kubernetes.io/hostname": "custom.user-defined.example.com",
 			},
 			expect: map[string]string{
-				"external-dns.alpha.kubernetes.io/hostname": "acid-test-stg.test.db.example.com,test-stg.acid.db.example.com",
+				"external-dns.alpha.kubernetes.io/hostname": "custom.user-defined.example.com",
 			},
 		},
 		{
@@ -916,16 +916,16 @@ func TestServiceAnnotations(t *testing.T) {
 			},
 		},
 		{
-			about:                       "Replica with cluster annotations do not override external-dns annotations",
+			about:                       "Replica with user-defined external-dns annotation is preserved",
 			role:                        "replica",
 			enableReplicaLoadBalancerOC: true,
 			enableTeamIdClusterPrefix:   false,
 			operatorAnnotations:         make(map[string]string),
 			serviceAnnotations: map[string]string{
-				"external-dns.alpha.kubernetes.io/hostname": "wrong.external-dns-name.example.com",
+				"external-dns.alpha.kubernetes.io/hostname": "custom.user-defined-repl.example.com",
 			},
 			expect: map[string]string{
-				"external-dns.alpha.kubernetes.io/hostname": "acid-test-stg-repl.test.db.example.com,test-stg-repl.acid.db.example.com",
+				"external-dns.alpha.kubernetes.io/hostname": "custom.user-defined-repl.example.com",
 			},
 		},
 		{
diff --git a/pkg/cluster/k8sres.go b/pkg/cluster/k8sres.go
index 2eb867f06..37113f15e 100644
--- a/pkg/cluster/k8sres.go
+++ b/pkg/cluster/k8sres.go
@@ -2027,10 +2027,11 @@ func (c *Cluster) generateServiceAnnotations(role PostgresRole, spec *acidv1.Pos
 	annotations := c.getCustomServiceAnnotations(role, spec)
 
 	if c.shouldCreateLoadBalancerForService(role, spec) {
-		dnsName := c.dnsName(role)
-
-		// External DNS name annotation is not customizable
-		annotations[constants.ZalandoDNSNameAnnotation] = dnsName
+		// Only set the DNS annotation if not already defined by user in service annotations
+		if _, exists := annotations[constants.ZalandoDNSNameAnnotation]; !exists {
+			dnsName := c.dnsName(role)
+			annotations[constants.ZalandoDNSNameAnnotation] = dnsName
+		}
 	}
 
 	if len(annotations) == 0 {