Added custom messages for uptime alerts

internal/alerts/dispatcher.go

@@ -30,13 +30,16 @@ func (d *Dispatcher) OnTransition(check *config.Check, from, to checks.State, sn
 	if to == checks.StateUnknown {
 		return
 	}
-	msg := Render(d.selfID, check, from, to, snap)
 	alerts := d.cluster.EffectiveAlertsFor(check)
 	if len(alerts) == 0 && len(check.AlertIDs) > 0 {
 		d.logger.Printf("alerts: check %q references alerts but none resolved", check.Name)
 	}
 	for i := range alerts {
 		alert := alerts[i]
+		msg, err := RenderFor(&alert, d.selfID, check, from, to, snap)
+		if err != nil {
+			d.logger.Printf("alerts: %q template: %v — falling back to default", alert.Name, err)
+		}
 		if err := d.dispatchOne(&alert, msg); err != nil {
 			d.logger.Printf("alerts: %q via %s: %v", alert.Name, alert.Type, err)
 		}
@@ -44,15 +47,32 @@ func (d *Dispatcher) OnTransition(check *config.Check, from, to checks.State, sn
 }
 
 // Test sends a one-shot test message to the named alert. Returns an
-// error so the CLI can surface failures interactively.
+// error so the CLI can surface failures interactively. If the alert
+// carries custom templates they are exercised against a synthetic
+// "homepage going DOWN" transition so the operator can confirm the
+// template renders before a real outage.
 func (d *Dispatcher) Test(alertID string) error {
 	alert := d.cluster.FindAlert(alertID)
 	if alert == nil {
 		return fmt.Errorf("alert %q not found", alertID)
 	}
-	msg := Message{
-		Subject: "[quptime] test alert",
-		Body:    fmt.Sprintf("This is a test of alert %q from node %s.\nIf you see this, the alert channel is wired correctly.\n", alert.Name, d.selfID),
+	if alert.SubjectTemplate == "" && alert.BodyTemplate == "" {
+		msg := Message{
+			Subject: "[quptime] test alert",
+			Body:    fmt.Sprintf("This is a test of alert %q from node %s.\nIf you see this, the alert channel is wired correctly.\n", alert.Name, d.selfID),
+		}
+		return d.dispatchOne(alert, msg)
+	}
+	sample := &config.Check{
+		ID:     "test-check",
+		Name:   "test-check",
+		Type:   config.CheckHTTP,
+		Target: "https://example.com",
+	}
+	snap := checks.Snapshot{Reports: 3, OKCount: 0, NotOK: 3, Detail: "synthetic test failure"}
+	msg, err := RenderFor(alert, d.selfID, sample, checks.StateUp, checks.StateDown, snap)
+	if err != nil {
+		return fmt.Errorf("render template: %w", err)
 	}
 	return d.dispatchOne(alert, msg)
 }