Fix: use event.fail() instead of set_results(success=False)

Author: arjun11-malik

lib/charms/mysql/v0/mysql.py

@@ -571,23 +571,27 @@ def _on_set_password(self, event: ActionEvent) -> None:
 
     def _get_cluster_status(self, event: ActionEvent) -> None:
         """Action used  to retrieve the cluster status."""
-        if event.params.get("cluster-set"):
-            logger.debug("Getting cluster set status")
-            status = self._mysql.get_cluster_set_status(extended=0)
-        else:
-            logger.debug("Getting cluster status")
-            status = self._mysql.get_cluster_status()
+        try:
+            if event.params.get("cluster-set"):
+                logger.debug("Getting cluster set status")
+                status = self._mysql.get_cluster_set_status(extended=0)
+            else:
+                logger.debug("Getting cluster status")
+                status = self._mysql.get_cluster_status()
 
-        if status:
-            event.set_results({
-                "success": True,
-                "status": status,
-            })
-        else:
-            event.set_results({
-                "success": False,
-                "message": "Failed to read cluster status.  See logs for more information.",
-            })
+        except Exception:
+            logger.exception("Failed to read cluster status")
+            event.fail("Failed to read cluster status. See logs for more information.")
+            return
+
+        if not status:
+            event.fail("Failed to read cluster status. See logs for more information.")
+            return
+
+        event.set_results({
+            "success": True,
+            "status": status,
+        })
 
     def _on_promote_to_primary(self, event: ActionEvent) -> None:
         """Action for setting this unit as the cluster primary."""

tests/unit/test_action_get_cluster_status.py

@@ -0,0 +1,82 @@
+# Copyright 2025 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+from unittest.mock import Mock, PropertyMock, patch
+
+import pytest
+from ops.charm import ActionEvent
+from ops.testing import Harness
+
+from charm import MySQLOperatorCharm
+
+
+class FakeMySQLBackend:
+    """Simulates the real MySQL backend, either returning a dict or raising."""
+
+    def __init__(self, response=None, error=None):
+        self._response = response
+        self._error = error
+
+    def get_cluster_status(self):
+        """Return the preset response or raise the preset error."""
+        if self._error:
+            raise self._error
+        return self._response
+
+
+@pytest.fixture
+def harness():
+    """Start the charm so harness.charm exists and peer databag works."""
+    h = Harness(MySQLOperatorCharm)
+    h.begin()
+    return h
+
+
+def make_event():
+    """Create a dummy ActionEvent with spies on set_results() and fail()."""
+    evt = Mock(spec=ActionEvent)
+    evt.set_results = Mock()
+    evt.fail = Mock()
+    evt.params = {}  # ensure .params.get() won’t AttributeError
+    return evt
+
+
+def test_get_cluster_status_action_success(harness):
+    """On success, the action wraps and forwards the status dict."""
+    # Prepare peer-databag so handler finds a cluster-name
+    rel = harness.add_relation("database-peers", "database-peers")
+    harness.update_relation_data(rel, harness.charm.app.name, {"cluster-name": "my-cluster"})
+
+    # Patch out the MySQL backend to return a known dict
+    sample = {"clusterrole": "primary", "status": "ok"}
+    fake = FakeMySQLBackend(response=sample)
+    with patch.object(MySQLOperatorCharm, "_mysql", new_callable=PropertyMock, return_value=fake):
+        evt = make_event()
+
+        # Invoke the action
+        harness.charm._get_cluster_status(evt)
+
+        # Expect set_results called once with {'success': True, 'status': sample}
+        evt.set_results.assert_called_once_with({"success": True, "status": sample})
+        evt.fail.assert_not_called()
+
+
+def test_get_cluster_status_action_failure(harness):
+    """On backend error, the action calls event.fail() and does not set_results()."""
+    # Seed peer-databag for cluster-name lookup
+    rel = harness.add_relation("database-peers", "database-peers")
+    harness.update_relation_data(rel, harness.charm.app.name, {"cluster-name": "my-cluster"})
+
+    # Patch MySQL backend to always raise
+    fake = FakeMySQLBackend(error=RuntimeError("boom"))
+    with patch.object(MySQLOperatorCharm, "_mysql", new_callable=PropertyMock, return_value=fake):
+        evt = make_event()
+
+        # Invoke the action
+        harness.charm._get_cluster_status(evt)
+
+        # It should report failure and never set_results
+        evt.fail.assert_called_once_with(
+            "Failed to read cluster status. See logs for more information."
+        )
+        evt.set_results.assert_not_called()