send http 202 accepted if import is taking a long time

backend/src/api/import-from-ss.js

@@ -201,11 +201,20 @@ module.exports = async (req, res) => {
     console.log(`importFromSS: author ${authorId}`);
     const papers = await fetchAuthorPapers(authorId);
     console.log('papers count:', papers.length);
+
+    const earlyResponseTimeout = setTimeout(() => {
+      res.status(202).end();
+    });
+
     const result = await Promise.mapSeries(papers, importPaper);
+    clearTimeout(earlyResponseTimeout);
+
     if (result.length) {
       console.log(`Added posts for ${result.length} papers by author ${authorId}`);
     }
-    res.json(result);
+    if (!res.headersSent) {
+      res.json(result);
+    }
   } else {
     res.status(400).end();
   }

backend/src/api/index.js

@@ -39,7 +39,9 @@ app.use((err, req, res, next) => {
   const status = err.response?.status ?? err.status ?? 500;
   const message = err.response?.data?.error ?? err.message;
   console.error(`error: ${message}`, err);
-  res.status(status).send(message);
+  if (!res.headersSent) {
+    res.status(status).send(message);
+  }
   next();
 });