feat: add graceful shutdown drain for /api/exports

src/routes/exports.ts

@@ -12,10 +12,56 @@
  * /api/exports             — Prediction history export (default alias)
  */
 
-import { Router } from "express";
+import { Router, type Request, type Response, type NextFunction } from "express";
 import { requireAuth } from "../middleware/requireAuth";
 import { createPerUserTokenBucketLimiter } from "../middleware/rateLimit";
 import { exportsPredictionsRouter } from "./exports/predictions";
+import { logger } from "../config/logger";
+
+// In-flight request tracking for graceful shutdown drain
+let inFlightExportsRequests = 0;
+
+/**
+ * Wait for all in-flight /api/exports requests to finish.
+ * @param timeoutMs Maximum time to wait before forcing resolution
+ */
+export async function drainExportsRequests(timeoutMs = 10000): Promise<void> {
+  const start = Date.now();
+  if (inFlightExportsRequests === 0) {
+    logger.info("No in-flight /api/exports requests to drain");
+    return;
+  }
+
+  logger.info({ inFlight: inFlightExportsRequests }, "Draining in-flight /api/exports requests...");
+
+  while (inFlightExportsRequests > 0) {
+    if (Date.now() - start > timeoutMs) {
+      logger.warn({ inFlight: inFlightExportsRequests }, "Timeout waiting for /api/exports requests to drain");
+      break;
+    }
+    // Poll every 50ms
+    await new Promise((resolve) => setTimeout(resolve, 50));
+  }
+
+  if (inFlightExportsRequests === 0) {
+    logger.info("Successfully drained all /api/exports requests");
+  }
+}
+
+function exportsInFlightMiddleware(_req: Request, res: Response, next: NextFunction): void {
+  inFlightExportsRequests++;
+  let finished = false;
+  const cleanup = () => {
+    if (!finished) {
+      finished = true;
+      inFlightExportsRequests = Math.max(0, inFlightExportsRequests - 1);
+    }
+  };
+
+  res.once("finish", cleanup);
+  res.once("close", cleanup);
+  next();
+}
 
 export interface ExportsRouterOptions {
   rateLimit?: {
@@ -27,6 +73,7 @@ export interface ExportsRouterOptions {
 export function createExportsRouter(options: ExportsRouterOptions = {}): Router {
   const router = Router();
 
+  router.use(exportsInFlightMiddleware);
   router.use(requireAuth);
   router.use(
     createPerUserTokenBucketLimiter({

src/server.ts

@@ -10,10 +10,11 @@
 import { reconciliationWorker } from "./workers/reconciliationWorker";
 import { startSlowQueryAlerter } from "./workers/slowQueryAlerter";
 import { drainSearchRequests } from "./routes/search";
+import { drainExportsRequests } from "./routes/exports";
 
 const app = createApp();
 let webhookWorker: WebhookWorker | null = null;
 let probeHandle: ReturnType<typeof setInterval> | null = null;
 
 connectWithRetry()
   .then(() => {
@@ -41,6 +42,8 @@
 
       // Ensure in-flight /api/search requests finish
       await drainSearchRequests(4000);
+      // Ensure in-flight /api/exports requests finish
+      await drainExportsRequests(4000);
 
       stopScheduler();
       await closeDb();