Update sync nodes during upgrade

src/charm.py

@@ -405,7 +405,7 @@ def _on_get_primary(self, event: ActionEvent) -> None:
         except RetryError as e:
             logger.error(f"failed to get primary with error {e}")
 
-    def _updated_synchronous_node_count(self, num_units: int | None = None) -> bool:
+    def updated_synchronous_node_count(self, num_units: int | None = None) -> bool:
         """Tries to update synchronous_node_count configuration and reports the result."""
         try:
             self._patroni.update_synchronous_node_count(num_units)
@@ -439,7 +439,7 @@ def _on_peer_relation_departed(self, event: RelationDepartedEvent) -> None:
 
         if "cluster_initialised" not in self._peers.data[
             self.app
-        ] or not self._updated_synchronous_node_count(len(self._units_ips)):
+        ] or not self.updated_synchronous_node_count(len(self._units_ips)):
             logger.debug("Deferring on_peer_relation_departed: cluster not initialized")
             event.defer()
             return

src/upgrade.py

@@ -146,6 +146,7 @@ def _on_upgrade_granted(self, event: UpgradeGrantedEvent) -> None:
         # Update the configuration.
         self.charm.unit.status = MaintenanceStatus("updating configuration")
         self.charm.update_config()
+        self.charm.updated_synchronous_node_count(len(self.charm._units_ips))
 
         self.charm.unit.status = MaintenanceStatus("refreshing the snap")
         self.charm._install_snap_packages(packages=SNAP_PACKAGES, refresh=True)

tests/unit/test_charm.py

@@ -2189,7 +2189,7 @@ def test_on_peer_relation_departed(harness):
         patch("charm.Patroni.are_all_members_ready") as _are_all_members_ready,
         patch("charm.PostgresqlOperatorCharm._get_ips_to_remove") as _get_ips_to_remove,
         patch(
-            "charm.PostgresqlOperatorCharm._updated_synchronous_node_count"
+            "charm.PostgresqlOperatorCharm.updated_synchronous_node_count"
         ) as _updated_synchronous_node_count,
         patch("charm.Patroni.remove_raft_member") as _remove_raft_member,
         patch("charm.PostgresqlOperatorCharm._unit_ip") as _unit_ip,

tests/unit/test_upgrade.py

@@ -106,6 +106,9 @@ def test_on_upgrade_granted(harness):
         patch("charm.Patroni.start_patroni") as _start_patroni,
         patch("charm.PostgresqlOperatorCharm._install_snap_packages") as _install_snap_packages,
         patch("charm.PostgresqlOperatorCharm.update_config") as _update_config,
+        patch(
+            "charm.PostgresqlOperatorCharm.updated_synchronous_node_count"
+        ) as _updated_synchronous_node_count,
     ):
         # Test when the charm fails to start Patroni.
         mock_event = MagicMock()
@@ -174,6 +177,7 @@ def test_on_upgrade_granted(harness):
         _member_started.reset_mock()
         _cluster_members.reset_mock()
         mock_event.defer.reset_mock()
+        _updated_synchronous_node_count.reset_mock()
         _is_replication_healthy.return_value = True
         with harness.hooks_disabled():
             harness.set_leader(True)
@@ -184,6 +188,7 @@ def test_on_upgrade_granted(harness):
         _set_unit_completed.assert_called_once()
         _set_unit_failed.assert_not_called()
         _on_upgrade_changed.assert_called_once()
+        _updated_synchronous_node_count.assert_called_once_with(2)
 
 
 def test_pre_upgrade_check(harness):