fix(nodes): 节点健康/connect 绑定 agent 在线状态,不再伪装连上

本次 google 打不开暴露:agent 离线 6 天,节点却一直显示健康、还让客户端
"连上"(凭证推送失败被 _ = 吞掉),实际节点不认 UUID。三处收口:

- Hub.IsOnline(nodeUUID):基于本地 agent 流注册的存活信号(单实例权威;
  多实例需 Redis presence,另议)。
- ListNodes:effectiveNodeStatus 把 DB='up' 但 agent 离线的节点降级为
  "down",不再永远显示健康(status 列只反映供给/调度,不反映 agent 死活)。
- ConnectNode:agent 离线即 503 ErrNodeUnavailable(凭证持久化留待 resync),
  在线时 push 失败也 503——不再吞 pushErr、不再下发节点无法兑现的配置。

测试:TestHub_IsOnline(注册/结束/未注册)、TestEffectiveNodeStatus
(up+离线→down 等)。新增 apierr.ErrNodeUnavailable(503)。

掉线告警 + 静默吞错全量审计另起 TODO。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/internal/httpapi/nodes.go

@@ -46,12 +46,24 @@ type nodeResponse struct {
 	NameZH string `json:"name_zh"`
 	NameEN string `json:"name_en"`
 	Tier   string `json:"tier"`   // "free" | "pro"
-	Status string `json:"status"` // always "up" in this endpoint
+	Status string `json:"status"` // "up" only when the agent is also online; "down" otherwise
 	// host/port 暴露节点入口,供客户端实测真实延迟(per-client ping 服务端无法代知)。
 	Host string `json:"host"`
 	Port int    `json:"port"`
 }
 
+// effectiveNodeStatus downgrades a DB-'up' node to "down" when its agent is
+// offline. The DB status column reflects provisioning/scheduler state, NOT agent
+// liveness — without this, a node whose agent has been offline for days still
+// shows healthy (the gap that hid a 6-day agent outage and let clients "connect"
+// to a node that couldn't serve them).
+func effectiveNodeStatus(dbStatus string, agentOnline bool) string {
+	if dbStatus == "up" && !agentOnline {
+		return "down"
+	}
+	return dbStatus
+}
+
 // ListNodes handles GET /v1/nodes.
 func (a *NodeAPI) ListNodes(w http.ResponseWriter, r *http.Request) {
 	nodeRows, err := a.store.ListUp(r.Context())
@@ -73,7 +85,7 @@ func (a *NodeAPI) ListNodes(w http.ResponseWriter, r *http.Request) {
 			NameZH: n.NameZH,
 			NameEN: n.NameEN,
 			Tier:   n.Tier,
-			Status: n.Status,
+			Status: effectiveNodeStatus(n.Status, a.hub == nil || a.hub.IsOnline(n.UUID)),
 			Host:   host,
 			Port:   port,
 		})
@@ -189,21 +201,34 @@ func (a *NodeAPI) ConnectNode(w http.ResponseWriter, r *http.Request) {
 		ExpiresAtUnix: expiresAt.Unix(),
 	}
 
-	// 5. Push to the node agent via Hub (real gRPC channel).
-	pushErr := a.hub.Push(r.Context(), node.UUID, &agentv1.Command{
-		Type:   agentv1.CommandTypeUpsert,
-		Upsert: &agentv1.UpsertPayload{Credential: cred},
-	})
-	if pushErr != nil {
-		// Non-fatal: command is queued in Redis and will be replayed on reconnect.
-		// Log but don't abort — return the config so the client can attempt the tunnel.
-		_ = pushErr
+	// 5. Refuse early if the node's agent is offline. A credential we can't push
+	//    now leaves the client "connected" to a node that rejects its UUID — the
+	//    exact failure that hid a 6-day agent outage. Persist it so the agent
+	//    applies it on resync, then signal unavailable instead of faking success.
+	if !a.hub.IsOnline(node.UUID) {
+		if persistErr := a.store.PersistCredential(r.Context(), node.ID, cred, expiresAt); persistErr != nil {
+			slog.Error("connect: persist credential (agent offline) failed", "node", nodeUUID, "user", uid, "err", persistErr)
+		}
+		slog.Warn("connect: node agent offline, refusing connect", "node", nodeUUID, "user", uid)
+		apierr.WriteJSON(w, http.StatusServiceUnavailable, apierr.ErrNodeUnavailable)
+		return
 	}
 
-	// 6. Persist credential for agent resync.
+	// 6. Push to the node agent via Hub. The agent is online, so a push failure is
+	//    a real error — surface it, don't pretend the tunnel will work.
+	if pushErr := a.hub.Push(r.Context(), node.UUID, &agentv1.Command{
+		Type:   agentv1.CommandTypeUpsert,
+		Upsert: &agentv1.UpsertPayload{Credential: cred},
+	}); pushErr != nil {
+		slog.Error("connect: push credential to agent failed", "node", nodeUUID, "user", uid, "err", pushErr)
+		apierr.WriteJSON(w, http.StatusServiceUnavailable, apierr.ErrNodeUnavailable)
+		return
+	}
+
+	// 7. Persist credential for agent resync (best-effort; the push above already
+	//    delivered it to the live agent).
 	if persistErr := a.store.PersistCredential(r.Context(), node.ID, cred, expiresAt); persistErr != nil {
-		// Non-fatal: tunnel still works via Hub push; resync will miss it on agent restart.
-		_ = persistErr
+		slog.Error("connect: persist credential failed", "node", nodeUUID, "user", uid, "err", persistErr)
 	}
 
 	// 7. Render and return the full sing-box CLIENT config JSON.

server/internal/httpapi/nodes_status_test.go

@@ -0,0 +1,26 @@
+package httpapi
+
+import "testing"
+
+// TestEffectiveNodeStatus guards the "don't show a node healthy when its agent is
+// offline" fix: a DB-'up' node with an offline agent must report "down".
+func TestEffectiveNodeStatus(t *testing.T) {
+	cases := []struct {
+		name   string
+		db     string
+		online bool
+		want   string
+	}{
+		{"up + agent online", "up", true, "up"},
+		{"up + agent offline → down", "up", false, "down"}, // the core fix
+		{"draining untouched when offline", "draining", false, "draining"},
+		{"down stays down", "down", true, "down"},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if got := effectiveNodeStatus(c.db, c.online); got != c.want {
+				t.Errorf("effectiveNodeStatus(%q, %v) = %q, want %q", c.db, c.online, got, c.want)
+			}
+		})
+	}
+}