Instrument API timing and reduce detail fallbacks

frontend/app/api/ops/online-users/route.ts

@@ -5,27 +5,45 @@ import {
 } from "@/lib/backend-auth";
 import { buildProxyExceptionResponse } from "@/lib/api-proxy";
 import { requireOpsProxyAuth } from "@/lib/ops-proxy-auth";
+import {
+  createProxyTimer,
+  finishProxyTimedResponse,
+} from "@/lib/proxy-timing";
 
 const API_BASE = process.env.POLYWEATHER_API_BASE_URL;
 
 export async function GET(req: NextRequest) {
+  const timer = createProxyTimer(req, "ops_online_users");
   if (!API_BASE) {
-    return NextResponse.json(
-      { error: "POLYWEATHER_API_BASE_URL is not configured" },
-      { status: 500 },
+    return finishProxyTimedResponse(
+      NextResponse.json(
+        { error: "POLYWEATHER_API_BASE_URL is not configured" },
+        { status: 500 },
+      ),
+      timer,
+      "missing_api_base",
     );
   }
 
   try {
-    const auth = await buildBackendRequestHeaders(req);
-    const authError = requireOpsProxyAuth(req, auth);
-    if (authError) return authError;
+    const auth = await timer.measure("auth_headers", () =>
+      buildBackendRequestHeaders(req),
+    );
+    const authError = timer.measureSync("ops_auth", () =>
+      requireOpsProxyAuth(req, auth),
+    );
+    if (authError) {
+      return finishProxyTimedResponse(authError, timer, "ops_auth_error");
+    }
 
-    const res = await fetch(`${API_BASE}/api/ops/online-users`, {
-      headers: auth.headers,
-      cache: "no-store",
-    });
-    const raw = await res.text();
+    const res = await timer.measure("backend_fetch", () =>
+      fetch(`${API_BASE}/api/ops/online-users`, {
+        headers: auth.headers,
+        cache: "no-store",
+      }),
+    );
+    const backendServerTiming = res.headers.get("server-timing") || "";
+    const raw = await timer.measure("backend_read", () => res.text());
     const response = new NextResponse(raw, {
       status: res.status,
       headers: {
@@ -33,10 +51,19 @@ export async function GET(req: NextRequest) {
         "Cache-Control": "no-store",
       },
     });
-    return applyAuthResponseCookies(response, auth.response);
+    return finishProxyTimedResponse(
+      applyAuthResponseCookies(response, auth.response),
+      timer,
+      res.ok ? "ok" : `upstream_${res.status}`,
+      { backendServerTiming },
+    );
   } catch (error) {
-    return buildProxyExceptionResponse(error, {
-      publicMessage: "Failed to fetch online users",
-    });
+    return finishProxyTimedResponse(
+      buildProxyExceptionResponse(error, {
+        publicMessage: "Failed to fetch online users",
+      }),
+      timer,
+      "exception",
+    );
   }
 }