feat: implement background cache updater for RSVP count with improved error handling

Author: boykisserchan

src/pages/api/rsvp.ts

@@ -1,71 +1,78 @@
 // src/pages/api/rsvp.ts
 import { NextApiRequest, NextApiResponse } from "next";
 
-async function getCount() {
-  let offset;
+// Rewritten to ensure a single background updater reloads the cached count every 30s.
+
+async function getCount(): Promise<number> {
+  let offset: string | undefined;
   let count = 0;
 
   do {
     const url = new URL(`https://api.airtable.com/v0/${process.env.RSVP_AIRTABLE_BASE_ID}/RSVPs`);
     if (offset) url.searchParams.set("offset", offset);
 
-    const res = await fetch(url, {
+    const res = await fetch(url.toString(), {
       headers: {
         Authorization: `Bearer ${process.env.RSVP_AIRTABLE_API_KEY}`,
       },
     });
+
     if (!res.ok) {
-      console.error(res.statusText);
-      throw new Error(res.statusText);
+      const text = await res.text().catch(() => res.statusText);
+      console.error("Airtable request failed:", res.status, text);
+      throw new Error(text || "Airtable request failed");
     }
+
     const data = await res.json();
-    count += data.records?.length ?? 0;
+    count += (data.records?.length ?? 0);
     offset = data.offset;
 
-    if (offset) await new Promise((resolve) => setTimeout(resolve, 200));
+    if (offset) await new Promise((r) => setTimeout(r, 200));
   } while (offset);
 
   return count;
 }
 
-let cached = { value: -1, updated: 0 };
+type Cache = { value: number | null; updated: number };
+let cached: Cache = { value: null, updated: 0 };
 
-// Cache duration in milliseconds
-const CACHE_DURATION = 30000;
+// Default cache duration 30 seconds; can be overridden with env var (ms)
+const CACHE_DURATION_MS = Number(process.env.RSVP_CACHE_DURATION_MS) || 30_000;
 
 // Extend global to hold a single timer across module reloads (avoid duplicate timers in dev)
 declare global {
+   
   var __RSVP_CACHE_TIMER__: NodeJS.Timeout | undefined;
 }
 
-async function updateCache() {
+async function updateCache(): Promise<void> {
   try {
     const count = await getCount();
     cached = { value: count, updated: Date.now() };
-    console.log("cached value", cached.value, "updatedAt", new Date(cached.updated).toISOString());
+    console.info("[rsvp] cache updated:", cached.value, new Date(cached.updated).toISOString());
   } catch (err: unknown) {
-    console.error("updateCache failed:", err);
-    // keep previous cached value
+    console.error("[rsvp] updateCache failed:", err);
+    // keep previous cached value if any
   }
 }
 
 // Start background updater once per server instance
 if (!global.__RSVP_CACHE_TIMER__) {
   // initial immediate update (fire-and-forget)
-  updateCache().catch((e) => console.error("initial update failed:", e));
+  updateCache().catch((e) => console.error("[rsvp] initial update failed:", e));
 
   // schedule periodic updates
   global.__RSVP_CACHE_TIMER__ = setInterval(() => {
-    updateCache().catch((e) => console.error("scheduled update failed:", e));
-  }, CACHE_DURATION);
+    updateCache().catch((e) => console.error("[rsvp] scheduled update failed:", e));
+  }, CACHE_DURATION_MS);
 }
 
 // Cleanup function to clear the background timer
-export function shutdownRSVPTimer() {
+export function shutdownRSVPTimer(): void {
   if (global.__RSVP_CACHE_TIMER__) {
     clearInterval(global.__RSVP_CACHE_TIMER__);
     global.__RSVP_CACHE_TIMER__ = undefined;
-    console.log("RSVP cache timer cleared.");
+    console.info("[rsvp] RSVP cache timer cleared.");
   }
 }
 
@@ -75,10 +82,15 @@ if (typeof process !== "undefined" && process.on) {
   process.on("SIGINT", shutdownRSVPTimer);
   process.on("exit", shutdownRSVPTimer);
 }
+
 export default function handler(_req: NextApiRequest, res: NextApiResponse) {
-  if (cached.value === -1) {
+  if (cached.value === null) {
     res.status(503).json({ error: "Service Unavailable: RSVP count not yet available." });
     return;
   }
-  res.status(200).json({ count: cached.value, updatedAt: cached.updated });
+
+  res.status(200).json({
+    count: cached.value,
+    updatedAt: new Date(cached.updated).toISOString(),
+  });
 }