notify: fix race of writing to Alert.WasSilenced

notify/notify.go

@@ -318,7 +318,7 @@ func (n *InhibitStage) Exec(ctx context.Context, alerts ...*types.Alert) (contex
 			// TODO(fabxc): increment muted alerts counter.
 			filtered = append(filtered, a)
 			// Store whether a previously inhibited alert is firing again.
-			a.WasInhibited = ok
+			a.SetInhibited(ok)
 		}
 	}
 
@@ -359,7 +359,7 @@ func (n *SilenceStage) Exec(ctx context.Context, alerts ...*types.Alert) (contex
 			filtered = append(filtered, a)
 			n.marker.SetSilenced(a.Labels.Fingerprint())
 			// Store whether a previously silenced alert is firing again.
-			a.WasSilenced = ok
+			a.SetSilenced(ok)
 		} else {
 			ids := make([]string, len(sils))
 			for i, s := range sils {

types/types.go

@@ -240,8 +240,10 @@ type Alert struct {
 	// The authoritative timestamp.
 	UpdatedAt    time.Time
 	Timeout      bool
-	WasSilenced  bool `json:"-"`
-	WasInhibited bool `json:"-"`
+	wasSilenced  bool
+	wasInhibited bool
+
+	mtx *sync.RWMutex
 }
 
 // AlertSlice is a sortable slice of Alerts.
@@ -262,11 +264,41 @@ func Alerts(alerts ...*Alert) model.Alerts {
 		if a.Timeout && !a.Resolved() {
 			v.EndsAt = time.Time{}
 		}
+
+		a.mtx = &sync.RWMutex{}
 		res = append(res, &v)
 	}
 	return res
 }
 
+func (a *Alert) SetSilenced(wasSilenced bool) {
+	a.mtx.Lock()
+	defer a.mtx.Unlock()
+
+	a.wasSilenced = wasSilenced
+}
+
+func (a *Alert) WasSilenced() bool {
+	a.mtx.RLock()
+	defer a.mtx.RUnlock()
+
+	return a.wasSilenced
+}
+
+func (a *Alert) SetInhibited(wasInhibited bool) {
+	a.mtx.Lock()
+	defer a.mtx.Unlock()
+
+	a.wasInhibited = wasInhibited
+}
+
+func (a *Alert) WasInhibited() bool {
+	a.mtx.RLock()
+	defer a.mtx.RUnlock()
+
+	return a.wasInhibited
+}
+
 // Merge merges the timespan of two alerts based and overwrites annotations
 // based on the authoritative timestamp.  A new alert is returned, the labels
 // are assumed to be equal.