perf: avoid needless downloads and track request latency (#876)

* perf: avoid needless downloads and track request latency

* fix: correct request timing and monitoring revalidation

test/monitoring-access.test.js

@@ -0,0 +1,32 @@
+const { expect } = require("chai");
+const express = require("express");
+const http = require("node:http");
+require("ts-node/register/transpile-only");
+const utils = require("../src/server/routes/route-utils");
+const admin = require("../src/server/routes/admin").default;
+
+describe("performance report access", function () {
+  let server, original;
+  before(async function () {
+    original = utils.getUser;
+    utils.getUser = async req => ({ isAdmin: req.get("x-fixture-user") === "admin", model: { id: "fixture" } });
+    const app = express();
+    app.use((req, _res, next) => { req.isAuthenticated = () => !!req.get("x-fixture-user"); next(); });
+    app.use("/api/admin", admin);
+    server = await new Promise(resolve => { const s = app.listen(0, "127.0.0.1", () => resolve(s)); });
+  });
+  after(async function () { server.closeAllConnections(); await new Promise(resolve => server.close(resolve)); utils.getUser = original; });
+  async function request(user) {
+    return new Promise((resolve, reject) => {
+      http.get({ host: "127.0.0.1", port: server.address().port, path: "/api/admin/performance", headers: user ? { "x-fixture-user": user } : {} }, res => {
+        let body = ""; res.on("data", chunk => { body += chunk; }); res.on("end", () => resolve({ status: res.statusCode, body, headers: res.headers }));
+      }).on("error", reject);
+    });
+  }
+  it("rejects anonymous requests", async function () { expect((await request()).status).to.equal(401); });
+  it("rejects non-admin users", async function () { expect((await request("regular")).status).to.equal(401); });
+  it("allows admins and disables HTTP caching", async function () {
+    const result = await request("admin"); expect(result.status).to.equal(200);
+    expect(JSON.parse(result.body).available).to.equal(false); expect(result.headers["cache-control"]).to.equal("no-store");
+  });
+});