[Agent] Replace dockerapi container with Redis-based control bus

data/Dockerfiles/agent/internal/registry/registry.go

@@ -0,0 +1,97 @@
+// Package registry publishes per-node heartbeats to Redis so the backend can
+// enumerate live containers. Two keys per service:
+//
+//	ZSET  mailcow.nodes.<service>          score=unix_ts member=node_id
+//	HASH  mailcow.node.<service>.<node_id> { version, started_at, image, health* }
+//
+// Both keys have a 30s TTL refreshed every 10s. Deregister clears them on
+// graceful shutdown.
+package registry
+
+import (
+	"context"
+	"fmt"
+	"strconv"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// HealthSnapshotter returns the latest health probe result so the heartbeat
+// can attach it to each tick. Implemented by main.healthState.
+type HealthSnapshotter interface {
+	Snapshot() (ok bool, detail string, at time.Time)
+}
+
+// Heartbeat carries the metadata published with every refresh.
+type Heartbeat struct {
+	Service   string
+	NodeID    string
+	Version   string
+	StartedAt time.Time
+	Image     string
+	Health    HealthSnapshotter // optional; nil → omit health fields
+}
+
+func nodesKey(service string) string      { return "mailcow.nodes." + service }
+func nodeKey(service, node string) string { return "mailcow.node." + service + "." + node }
+
+// Publish writes one heartbeat tick. Callers run this in a loop.
+func Publish(ctx context.Context, rdb *redis.Client, h Heartbeat) error {
+	now := time.Now().Unix()
+	fields := map[string]any{
+		"version":    h.Version,
+		"started_at": h.StartedAt.UTC().Format(time.RFC3339),
+		"image":      h.Image,
+		"node_id":    h.NodeID,
+		"service":    h.Service,
+		"updated_at": strconv.FormatInt(now, 10),
+	}
+	if h.Health != nil {
+		ok, detail, at := h.Health.Snapshot()
+		if ok {
+			fields["health"] = "ok"
+		} else {
+			fields["health"] = "fail"
+		}
+		fields["health_detail"] = detail
+		fields["health_at"] = strconv.FormatInt(at.Unix(), 10)
+	}
+	pipe := rdb.Pipeline()
+	pipe.ZAdd(ctx, nodesKey(h.Service), redis.Z{Score: float64(now), Member: h.NodeID})
+	pipe.Expire(ctx, nodesKey(h.Service), 5*time.Minute)
+	pipe.HSet(ctx, nodeKey(h.Service, h.NodeID), fields)
+	pipe.Expire(ctx, nodeKey(h.Service, h.NodeID), 30*time.Second)
+	_, err := pipe.Exec(ctx)
+	if err != nil {
+		return fmt.Errorf("registry: heartbeat exec: %w", err)
+	}
+	return nil
+}
+
+// Deregister removes the node from the ZSET and deletes its detail hash.
+// Called on graceful shutdown so the dashboard reflects intentional stops
+// immediately rather than waiting for TTL.
+func Deregister(ctx context.Context, rdb *redis.Client, service, nodeID string) error {
+	pipe := rdb.Pipeline()
+	pipe.ZRem(ctx, nodesKey(service), nodeID)
+	pipe.Del(ctx, nodeKey(service, nodeID))
+	_, err := pipe.Exec(ctx)
+	return err
+}
+
+// Loop runs Publish on a ticker until ctx is done. It is the typical caller.
+func Loop(ctx context.Context, rdb *redis.Client, h Heartbeat, interval time.Duration) {
+	// Publish once immediately so the dashboard sees us right away.
+	_ = Publish(ctx, rdb, h)
+	t := time.NewTicker(interval)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-t.C:
+			_ = Publish(ctx, rdb, h)
+		}
+	}
+}