feat: initial backend service template

src/routes/health.ts

@@ -0,0 +1,35 @@
+import { Router } from "express";
+import type { Db } from "../lib/db.js";
+import type { Cache } from "../lib/redis.js";
+
+export function healthRouter(deps: { db?: Db; cache?: Cache }): Router {
+  const router = Router();
+
+  // Liveness: 200 whenever the process is listening.
+  router.get("/healthz", (_req, res) => {
+    res.type("text/plain").send("ok");
+  });
+
+  // Readiness: every configured backend must answer.
+  router.get("/readyz", async (_req, res) => {
+    const body: Record<string, string> = {};
+    let ready = true;
+    const check = async (name: string, fn?: () => Promise<void>) => {
+      if (!fn) return;
+      try {
+        await fn();
+        body[name] = "ok";
+      } catch (err) {
+        ready = false;
+        body[name] = `unavailable: ${(err as Error).message || "error"}`;
+      }
+    };
+    await check("postgres", deps.db && (() => deps.db!.ping()));
+    await check("redis", deps.cache && (() => deps.cache!.ping()));
+    res
+      .status(ready ? 200 : 503)
+      .json({ status: ready ? "ready" : "not-ready", ...body });
+  });
+
+  return router;
+}