[DPE-5934] Early exit on missing s3 rel (#762)

* Early exit on missing s3 rel

* Split of initial checks

src/backups.py

@@ -675,18 +675,21 @@ def _is_primary_pgbackrest_service_running(self) -> bool:
 
         return True
 
-    def _on_s3_credential_changed(self, event: CredentialsChangedEvent):
-        """Call the stanza initialization when the credentials or the connection info change."""
+    def _on_s3_credentials_checks(self, event: CredentialsChangedEvent) -> bool:
+        if not self.s3_client.get_s3_connection_info():
+            logger.debug("_on_s3_credential_changed early exit: no connection info")
+            return False
+
         if "cluster_initialised" not in self.charm.app_peer_data:
             logger.debug("Cannot set pgBackRest configurations, PostgreSQL has not yet started.")
             event.defer()
-            return
+            return False
 
         # Prevents config change in bad state, so DB peer relations change event will not cause patroni related errors.
         if self.charm.unit.status.message == CANNOT_RESTORE_PITR:
             logger.info("Cannot change S3 configuration in bad PITR restore status")
             event.defer()
-            return
+            return False
 
         # Prevents S3 change in the middle of restoring backup and patroni / pgbackrest errors caused by that.
         if (
@@ -695,15 +698,21 @@ def _on_s3_credential_changed(self, event: CredentialsChangedEvent):
         ):
             logger.info("Cannot change S3 configuration during restore")
             event.defer()
-            return
+            return False
 
         if not self._render_pgbackrest_conf_file():
             logger.debug("Cannot set pgBackRest configurations, missing configurations.")
-            return
+            return False
 
         if not self._can_initialise_stanza:
             logger.debug("Cannot initialise stanza yet.")
             event.defer()
+            return False
+        return True
+
+    def _on_s3_credential_changed(self, event: CredentialsChangedEvent) -> bool | None:
+        """Call the stanza initialization when the credentials or the connection info change."""
+        if not self._on_s3_credentials_checks(event):
             return
 
         self.start_stop_pgbackrest_service()

tests/unit/test_backups.py

@@ -969,6 +969,9 @@ def test_on_s3_credential_changed(harness):
         patch(
             "charm.PostgreSQLBackups._on_s3_credential_changed_primary"
         ) as _on_s3_credential_changed_primary,
+        patch(
+            "backups.S3Requirer.get_s3_connection_info", return_value={}
+        ) as _get_s3_connection_info,
         patch("ops.framework.EventBase.defer") as _defer,
         patch(
             "charm.PostgresqlOperatorCharm.is_standby_leader", new_callable=PropertyMock
@@ -977,11 +980,19 @@ def test_on_s3_credential_changed(harness):
         patch("time.asctime", return_value="Thu Feb 24 05:00:00 2022"),
     ):
         peer_rel_id = harness.model.get_relation(PEER).id
-        # Test when the cluster was not initialised yet.
+        # Early exit when no s3 creds
         s3_rel_id = harness.add_relation(S3_PARAMETERS_RELATION, "s3-integrator")
         harness.charm.backup.s3_client.on.credentials_changed.emit(
             relation=harness.model.get_relation(S3_PARAMETERS_RELATION, s3_rel_id)
         )
+        _defer.assert_not_called()
+        _render_pgbackrest_conf_file.assert_not_called()
+
+        # Test when the cluster was not initialised yet.
+        _get_s3_connection_info.return_value = {"creds": "value"}
+        harness.charm.backup.s3_client.on.credentials_changed.emit(
+            relation=harness.model.get_relation(S3_PARAMETERS_RELATION, s3_rel_id)
+        )
         _defer.assert_called_once()
         _render_pgbackrest_conf_file.assert_not_called()