fix(callback_role): support custom Kubernetes cluster domains

Replace hardcoded cluster.local with KUBERNETES_SERVICE_HOST env var.

Users can now set custom cluster domains like:
- https://kubernetes.default.svc.cluster.bk1
- http://192.168.1.1:8443

Fully backwards compatible - defaults to previous behavior.

Fixes: patroni could not patch pod labels on clusters
with custom cluster domains.

Author: m.doulabi

postgres-appliance/scripts/callback_role.py

@@ -14,7 +14,7 @@
 KUBE_TOKEN_FILENAME = KUBE_SERVICE_DIR + 'token'
 KUBE_CA_CERT = KUBE_SERVICE_DIR + 'ca.crt'
 
-KUBE_API_URL = 'https://kubernetes.default.svc.cluster.local/api/v1/namespaces'
+KUBE_API_URL = os.environ.get('KUBERNETES_SERVICE_HOST', 'https://kubernetes.default.svc.cluster.local') + '/api/v1/namespaces'
 
 logger = logging.getLogger(__name__)
 
@@ -94,4 +94,4 @@ def main():
 
 
 if __name__ == '__main__':
-    main()
+    main()