Nextcloud seems to not be able to connect to redis with default settings

Describe your Issue

I have an issue with Nextcloud failing to connect to redis when it's enabled. Here's an excerpt from the logs:

{
  "reqId":"b8E9pguPPMd2bgHNOOj0",
  "level":3,
  "time":"2023-09-26T06:14:19+00:00",
  "remoteAddr":"10.42.5.1",
  "user":"--",
  "app":"PHP",
  "method":"GET",
  "url":"/status.php",
  "message":"session_start(): Failed to read session data: redis (path: tcp://nextcloud-redis-master:6379?auth=\<redacted\>) at /var/www/html/lib/private/Session/Internal.php#222",
  "userAgent":"kube-probe/1.27",
  "version":"27.1.1.0",
  "data":{"app":"PHP"}
}

Which is weird, because when I do nslookup, it seems to resolve fine:

$ nslookup nextcloud-redis-master
Server:         10.43.0.10
Address:        10.43.0.10#53

Name:   nextcloud-redis-master.cloud.svc.cluster.local
Address: 10.43.32.88

What I did as a workaround, was to hardcode the "host" part in redis.config.php as such: 'host' => "nextcloud-redis-master.cloud.svc.cluster.local",. Any ideas what might be wrong here?

Logs and Errors

Describe your Environment

• Kubernetes distribution: k3s

• Helm Version (or App that manages helm): 3.11.0

• Helm Chart Version: 3.5.22

• values.yaml:

nextcloud:
  defaultConfigs:
    redis.config.php: false
  configs:
    redis.config.php: |-
      <?php
      $CONFIG = array (
        'memcache.distributed' => '\OC\Memcache\Redis',
        'memcache.locking' => '\OC\Memcache\Redis',
        'redis' => array(
          'host' => "nextcloud-redis-master.cloud.svc.cluster.local",
          'port' => getenv('REDIS_HOST_PORT') ?: 6379,
          'password' => getenv('REDIS_HOST_PASSWORD'),
        ),
      );
redis:
    enabled: true
    usePassword: true
    auth:
      existingSecret: nextcloud-auth-config
      existingSecretPasswordKey: redis-password
    master:
      persistence:
        storageClass: longhorn-fast-retain
    replica:
      persistence:
        storageClass: longhorn-fast-retain

Start with the chart's redis.config.php and the values.yaml configuration shown in the report; inspect how the Redis hostname, port, and password are rendered and used. Reproduce the connection failure with the Helm chart on k3s, then verify that the default configuration connects without hardcoding the fully qualified hostname.