fix(aia,ssa,asl,infra): harden SSE transport and stabilize attachment context

Deliver SSE protocol hardening for SAE/HTTP2 paths, add graceful shutdown health behavior, and improve SSA retry UX for transient stream failures. For AIA, persist attachment extraction results in database with cache read-through fallback, plus production cache safety guard to prevent memory-cache drift in multi-instance deployments; also restore ASL SR page scrolling behavior.

Made-with: Cursor

backend/src/index.ts

@@ -15,7 +15,7 @@ import { aslRoutes } from './modules/asl/routes/index.js';
 import { registerDCRoutes, initDCModule } from './modules/dc/index.js';
 import pkbRoutes from './modules/pkb/routes/index.js';
 import { aiaRoutes } from './modules/aia/index.js';
-import { registerHealthRoutes } from './common/health/index.js';
+import { registerHealthRoutes, markShuttingDown } from './common/health/index.js';
 import { logger } from './common/logging/index.js';
 import { authRoutes, registerAuthPlugin } from './common/auth/index.js';
 import { promptRoutes } from './common/prompt/index.js';
@@ -339,11 +339,24 @@ start();
 // ============================================
 // 🛡️ 优雅关闭处理（Graceful Shutdown）
 // ============================================
+const SHUTDOWN_TIMEOUT_MS = 30_000;
+
 const gracefulShutdown = async (signal: string) => {
   console.log(`\n⚠️ 收到 ${signal} 信号，开始优雅关闭...`);
-  
+
+  // 立即标记停机，健康检查返回 503，CLB 不再派发新请求
+  markShuttingDown();
+  console.log('🚫 健康检查已切换为 503，CLB 将停止路由新流量');
+
+  // 强制超时兜底：防止 SSE 长连接或死循环任务阻塞退出
+  const forceTimer = setTimeout(() => {
+    console.error(`❌ 优雅关闭超时 (${SHUTDOWN_TIMEOUT_MS / 1000}s)，强制退出`);
+    process.exit(1);
+  }, SHUTDOWN_TIMEOUT_MS);
+  forceTimer.unref();
+
   try {
-    // 1. 停止接收新请求
+    // 1. 停止接收新请求（已有 SSE 连接继续跑完）
     await fastify.close();
     console.log('✅ HTTP 服务已停止');