Alerting: Fix bug where state did not change between Alerting and Error (#52204) (#52209)

This commit fixes a bug where the state did not change from Alerting to Error if the evaluation result returned an error, or from Error to Alerting if evaluations stopped returning errors.

(cherry picked from commit 34d45977ca)

Co-authored-by: George Robinson <george.robinson@grafana.com>

pkg/services/ngalert/state/manager_test.go

@@ -1552,6 +1552,103 @@ func TestProcessEvalResults(t *testing.T) {
 				},
 			},
 		},
+		{
+			desc: "normal -> alerting -> error when result is Error and ExecErrorState is Error",
+			alertRule: &models.AlertRule{
+				OrgID:           1,
+				Title:           "test_title",
+				UID:             "test_alert_rule_uid_2",
+				NamespaceUID:    "test_namespace_uid",
+				Annotations:     map[string]string{"annotation": "test"},
+				Labels:          map[string]string{"label": "test"},
+				IntervalSeconds: 10,
+				For:             20 * time.Second,
+				ExecErrState:    models.ErrorErrState,
+			},
+			evalResults: []eval.Results{
+				{
+					eval.Result{
+						Instance:           data.Labels{"instance_label": "test"},
+						State:              eval.Alerting,
+						EvaluatedAt:        evaluationTime,
+						EvaluationDuration: evaluationDuration,
+					},
+				},
+				{
+					eval.Result{
+						Instance:           data.Labels{"instance_label": "test"},
+						State:              eval.Alerting,
+						EvaluatedAt:        evaluationTime.Add(10 * time.Second),
+						EvaluationDuration: evaluationDuration,
+					},
+				},
+				{
+					eval.Result{
+						Instance:           data.Labels{"instance_label": "test"},
+						State:              eval.Alerting,
+						EvaluatedAt:        evaluationTime.Add(20 * time.Second),
+						EvaluationDuration: evaluationDuration,
+					},
+				},
+				{
+					eval.Result{
+						Instance:           data.Labels{"instance_label": "test"},
+						State:              eval.Error,
+						EvaluatedAt:        evaluationTime.Add(30 * time.Second),
+						EvaluationDuration: evaluationDuration,
+					},
+				},
+				{
+					eval.Result{
+						Instance:           data.Labels{"instance_label": "test"},
+						State:              eval.Error,
+						EvaluatedAt:        evaluationTime.Add(40 * time.Second),
+						EvaluationDuration: evaluationDuration,
+					},
+				},
+				{
+					eval.Result{
+						Instance:           data.Labels{"instance_label": "test"},
+						State:              eval.Error,
+						EvaluatedAt:        evaluationTime.Add(50 * time.Second),
+						EvaluationDuration: evaluationDuration,
+					},
+				},
+			},
+			expectedAnnotations: 3,
+			expectedStates: map[string]*state.State{
+				`[["__alert_rule_namespace_uid__","test_namespace_uid"],["__alert_rule_uid__","test_alert_rule_uid_2"],["alertname","test_title"],["instance_label","test"],["label","test"]]`: {
+					AlertRuleUID: "test_alert_rule_uid_2",
+					OrgID:        1,
+					CacheId:      `[["__alert_rule_namespace_uid__","test_namespace_uid"],["__alert_rule_uid__","test_alert_rule_uid_2"],["alertname","test_title"],["instance_label","test"],["label","test"]]`,
+					Labels: data.Labels{
+						"__alert_rule_namespace_uid__": "test_namespace_uid",
+						"__alert_rule_uid__":           "test_alert_rule_uid_2",
+						"alertname":                    "test_title",
+						"label":                        "test",
+						"instance_label":               "test",
+					},
+					State: eval.Error,
+					Results: []state.Evaluation{
+						{
+							EvaluationTime:  evaluationTime.Add(40 * time.Second),
+							EvaluationState: eval.Error,
+							Values:          make(map[string]*float64),
+						},
+						{
+							EvaluationTime:  evaluationTime.Add(50 * time.Second),
+							EvaluationState: eval.Error,
+							Values:          make(map[string]*float64),
+						},
+					},
+					StartsAt:           evaluationTime.Add(20 * time.Second),
+					EndsAt:             evaluationTime.Add(50 * time.Second).Add(state.ResendDelay * 3),
+					LastEvaluationTime: evaluationTime.Add(50 * time.Second),
+					EvaluationDuration: evaluationDuration,
+					Annotations:        map[string]string{"annotation": "test"},
+				},
+			},
+		},
 		{
 			desc: "normal -> alerting -> error -> alerting - it should clear the error",
 			alertRule: &models.AlertRule{

pkg/services/ngalert/state/state.go

@@ -122,6 +122,12 @@ func (a *State) resultError(alertRule *models.AlertRule, result eval.Result) {
 
 	switch a.State {
 	case eval.Alerting, eval.Error:
+		// We must set the state here as the state can change both from Alerting
+		// to Error and from Error to Alerting. This can happen when the datasource
+		// is unavailable or queries against the datasource returns errors, and is
+		// then resolved as soon as the datasource is available and queries return
+		// without error
+		a.State = execErrState
 		a.setEndsAt(alertRule, result)
 	case eval.Pending:
 		if result.EvaluatedAt.Sub(a.StartsAt) >= alertRule.For {