feat: add alertmanager handler

bridge/alertmanager.go

@@ -0,0 +1,70 @@
+package bridge
+
+import (
+	"encoding/json"
+	"log/slog"
+	"net/http"
+	"strings"
+	"time"
+)
+
+type AlertmanagerEvent struct {
+	Receiver string `json:"receiver"`
+	Status   string `json:"status"`
+	Alerts   []struct {
+		Status       string            `json:"status"`
+		Labels       map[string]string `json:"labels"`
+		Annotations  map[string]string `json:"annotations"`
+		StartsAt     time.Time         `json:"startsAt"`
+		EndsAt       time.Time         `json:"endsAt"`
+		GeneratorURL string            `json:"generatorURL"`
+		Fingerprint  string            `json:"fingerprint"`
+	} `json:"alerts"`
+	GroupLabels       map[string]string `json:"groupLabels"`
+	CommonLabels      map[string]string `json:"commonLabels"`
+	CommonAnnotations map[string]string `json:"commonAnnotations"`
+	ExternalURL       string            `json:"externalURL"`
+	Version           string            `json:"version"`
+	GroupKey          string            `json:"groupKey"`
+	TruncatedAlerts   int               `json:"truncatedAlerts"`
+}
+
+type AlertmanagerHandler struct{}
+
+func NewAlertmanagerHandler() AlertmanagerHandler {
+	return AlertmanagerHandler{}
+}
+
+func (d AlertmanagerHandler) ProduceNotifications(r *http.Request) ([]Notification, error) {
+	l := slog.With(slog.String("handler", "alertmanager"))
+
+	dec := json.NewDecoder(r.Body)
+	defer r.Body.Close()
+
+	var event AlertmanagerEvent
+	if err := dec.Decode(&event); err != nil {
+		l.Error("invalid message format", "error", err)
+		return nil, err
+	}
+
+	notifications := make([]Notification, 0, len(event.Alerts))
+	for _, alert := range event.Alerts {
+		if alert.Annotations["summary"] == "" {
+			continue
+		}
+
+		var not Notification
+		not.Title = "[" + strings.ToUpper(event.Status) + "] " + alert.Annotations["summary"]
+		not.Body = alert.Annotations["description"]
+		if runbook := alert.Annotations["runbook_url"]; runbook != "" {
+			not.Actions = append(not.Actions, NewViewAction("Runbook", runbook))
+		}
+		if event.Status == "resolved" {
+			not.Tags = []string{"resolved"}
+		}
+
+		notifications = append(notifications, not)
+	}
+
+	return notifications, nil
+}

config/config.go

@@ -12,6 +12,7 @@ type HandlerType int
 const (
 	HandlerFlux HandlerType = iota + 1
 	HandlerDiscordEmbed
+	HandlerAlertmanager
 )
 
 func (h HandlerType) String() string {
@@ -20,6 +21,8 @@ func (h HandlerType) String() string {
 		return "flux"
 	case HandlerDiscordEmbed:
 		return "discord_embed"
+	case HandlerAlertmanager:
+		return "alertmanager"
 	}
 	panic("unreachable")
 }
@@ -153,6 +156,8 @@ func readHandlerType(d *scfg.Directive) (HandlerType, error) {
 		return HandlerFlux, nil
 	case "discord_embed":
 		return HandlerDiscordEmbed, nil
+	case "alertmanager":
+		return HandlerAlertmanager, nil
 	default:
 		return 0, fmt.Errorf("invalid handler type %q", ty)
 	}

k8s/bridge.yaml

@@ -22,6 +22,11 @@ data:
         type "discord_embed"
         topic "forgejo"
     }
+
+    handler "/alerts" {
+        type "alertmanager"
+        topic "infra"
+    }
 ---
 apiVersion: apps/v1
 kind: Deployment

main.go

@@ -76,6 +76,8 @@ func main() {
 			h = bridge.NewFluxHandler()
 		case config.HandlerDiscordEmbed:
 			h = bridge.NewDiscordEmbedHandler()
+		case config.HandlerAlertmanager:
+			h = bridge.NewAlertmanagerHandler()
 		}
 
 		slog.Debug("Registering bridge", "route", route, "handler", handler.Type)