Add live server performance monitoring

server/request-monitor.test.js

@@ -0,0 +1,19 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { createRequestMonitor } from './request-monitor.js';
+
+test('request monitor records route latency, status errors, and current process health', async () => {
+  let t = 100;
+  const monitor = createRequestMonitor({ now: () => t, snapshotIntervalMs: 0, adapters: { media: () => ({ queued: 2 }) } });
+  const middleware = monitor.middleware();
+  const ctx = (path, status) => ({ req: { path }, res: { status } });
+  await middleware(ctx('/api/media/abc/status', 200), async () => { t += 8; });
+  await middleware(ctx('/api/media/xyz/status', 503), async () => { t += 12; });
+  const sample = await monitor.sample();
+  assert.equal(sample.routes['/api/media/:id/status'].requests, 2);
+  assert.equal(sample.routes['/api/media/:id/status'].errors, 1);
+  assert.equal(sample.routes['/api/media/:id/status'].p50, 8);
+  assert.equal(sample.media.queued, 2);
+  assert.ok(sample.rssBytes > 0);
+  monitor.close();
+});