Alerting: Improve error when receiver or time interval used by rule is deleted (#86865)

* Alerting: Improve error when receiver used by rule is deleted

* Remove RuleUID from public error and data

* Improve fallback error in am config post

* Refactor to expand to time intervals

* Fix message on unchecked errors to be same as before

pkg/services/ngalert/api/api_alertmanager.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/go-openapi/strfmt"
+
 	alertingNotify "github.com/grafana/alerting/notify"
 
 	"github.com/grafana/grafana/pkg/api/response"
@@ -304,7 +305,7 @@ func (srv AlertmanagerSrv) RoutePostAlertingConfig(c *contextmodel.ReqContext, b
 		return response.Error(http.StatusConflict, err.Error(), err)
 	}
 
-	return ErrResp(http.StatusInternalServerError, err, "")
+	return response.ErrOrFallback(http.StatusInternalServerError, err.Error(), err)
 }
 
 func (srv AlertmanagerSrv) RouteGetReceivers(c *contextmodel.ReqContext) response.Response {

pkg/services/ngalert/notifier/alertmanager_config.go

@@ -13,6 +13,20 @@ import (
 	"github.com/grafana/grafana/pkg/services/ngalert/models"
 	"github.com/grafana/grafana/pkg/services/ngalert/store"
 	"github.com/grafana/grafana/pkg/util"
+	"github.com/grafana/grafana/pkg/util/errutil"
+)
+
+var (
+	// ErrAlertmanagerReceiverInUse is primarily meant for when a receiver is used by a rule and is being deleted.
+	ErrAlertmanagerReceiverInUse = errutil.BadRequest("alerting.notifications.alertmanager.receiverInUse").MustTemplate("receiver [Name: {{ .Public.Receiver }}] is used by rule: {{ .Error }}",
+		errutil.WithPublic(
+			"receiver [Name: {{ .Public.Receiver }}] is used by rule",
+		))
+	// ErrAlertmanagerTimeIntervalInUse is primarily meant for when a time interval is used by a rule and is being deleted.
+	ErrAlertmanagerTimeIntervalInUse = errutil.BadRequest("alerting.notifications.alertmanager.intervalInUse").MustTemplate("time interval [Name: {{ .Public.Interval }}] is used by rule: {{ .Error }}",
+		errutil.WithPublic(
+			"time interval [Name: {{ .Public.Interval }}] is used by rule",
+		))
 )
 
 type UnknownReceiverError struct {
@@ -227,6 +241,14 @@ func (moa *MultiOrgAlertmanager) SaveAndApplyAlertmanagerConfiguration(ctx conte
 
 	if err := am.SaveAndApplyConfig(ctx, &config); err != nil {
 		moa.logger.Error("Unable to save and apply alertmanager configuration", "error", err)
+		errReceiverDoesNotExist := ErrorReceiverDoesNotExist{}
+		if errors.As(err, &errReceiverDoesNotExist) {
+			return ErrAlertmanagerReceiverInUse.Build(errutil.TemplateData{Public: map[string]interface{}{"Receiver": errReceiverDoesNotExist.Reference}, Error: err})
+		}
+		errTimeIntervalDoesNotExist := ErrorTimeIntervalDoesNotExist{}
+		if errors.As(err, &errTimeIntervalDoesNotExist) {
+			return ErrAlertmanagerTimeIntervalInUse.Build(errutil.TemplateData{Public: map[string]interface{}{"Interval": errTimeIntervalDoesNotExist.Reference}, Error: err})
+		}
 		return AlertmanagerConfigRejectedError{err}
 	}
 

pkg/services/ngalert/notifier/validation.go

@@ -6,13 +6,33 @@ import (
 	"fmt"
 	"sync"
 
+	"github.com/prometheus/alertmanager/config"
+
 	"github.com/grafana/grafana/pkg/infra/log"
 	"github.com/grafana/grafana/pkg/services/ngalert/api/tooling/definitions"
 	"github.com/grafana/grafana/pkg/services/ngalert/models"
 	"github.com/grafana/grafana/pkg/services/ngalert/store"
-	"github.com/prometheus/alertmanager/config"
 )
 
+type ErrorReferenceInvalid struct {
+	Reference string
+}
+
+type ErrorReceiverDoesNotExist struct {
+	ErrorReferenceInvalid
+}
+type ErrorTimeIntervalDoesNotExist struct {
+	ErrorReferenceInvalid
+}
+
+func (e ErrorReceiverDoesNotExist) Error() string {
+	return fmt.Sprintf("receiver %s does not exist", e.Reference)
+}
+
+func (e ErrorTimeIntervalDoesNotExist) Error() string {
+	return fmt.Sprintf("time interval %s does not exist", e.Reference)
+}
+
 // NotificationSettingsValidator validates NotificationSettings against the current Alertmanager configuration
 type NotificationSettingsValidator interface {
 	Validate(s models.NotificationSettings) error
@@ -64,11 +84,11 @@ func (n staticValidator) Validate(settings models.NotificationSettings) error {
 	}
 	var errs []error
 	if _, ok := n.availableReceivers[settings.Receiver]; !ok {
-		errs = append(errs, fmt.Errorf("receiver '%s' does not exist", settings.Receiver))
+		errs = append(errs, ErrorReceiverDoesNotExist{ErrorReferenceInvalid: ErrorReferenceInvalid{Reference: settings.Receiver}})
 	}
 	for _, interval := range settings.MuteTimeIntervals {
 		if _, ok := n.availableTimeIntervals[interval]; !ok {
-			errs = append(errs, fmt.Errorf("mute time interval '%s' does not exist", interval))
+			errs = append(errs, ErrorTimeIntervalDoesNotExist{ErrorReferenceInvalid: ErrorReferenceInvalid{Reference: interval}})
 		}
 	}
 	return errors.Join(errs...)