fix: propagate initialization errors and reduce request metrics

test/back/monitoring.test.cjs

@@ -0,0 +1,73 @@
+const assert = require('node:assert/strict');
+const test = require('node:test');
+
+const { monitoringMiddleware } = require('../../back/middlewares/monitoring');
+const { metricsService } = require('../../back/services/metrics');
+
+function createResponse() {
+  return {
+    statusCode: 200,
+    ended: false,
+    end() {
+      this.ended = true;
+    },
+  };
+}
+
+test('health probes bypass request metric retention with or without base URL', () => {
+  const before = metricsService.getMetrics('http_request', {
+    path: '/api/health',
+  }).count;
+  let nextCalled = false;
+
+  for (const path of ['/api/health', '/ql/api/health']) {
+    const response = createResponse();
+    monitoringMiddleware({ method: 'GET', path }, response, () => {
+      nextCalled = true;
+    });
+    response.end();
+    assert.equal(response.ended, true);
+  }
+
+  const after = metricsService.getMetrics('http_request', {
+    path: '/api/health',
+  }).count;
+  assert.equal(nextCalled, true);
+  assert.equal(after, before);
+});
+
+test('non-health requests keep bounded service metrics', () => {
+  const path = '/api/monitoring-test';
+  const before = metricsService.getMetrics('http_request', { path }).count;
+  const response = createResponse();
+
+  monitoringMiddleware(
+    { method: 'GET', path, platform: 'desktop' },
+    response,
+    () => {},
+  );
+  response.end();
+
+  const after = metricsService.getMetrics('http_request', { path }).count;
+  assert.equal(response.ended, true);
+  assert.equal(after, before + 1);
+});
+
+test('ordinary request metrics are sampled instead of retained per request', () => {
+  const path = '/api/monitoring-sampling-test';
+  const before = metricsService.getMetrics('http_request', { path }).count;
+
+  for (let index = 0; index < 30; index += 1) {
+    const response = createResponse();
+    monitoringMiddleware(
+      { method: 'GET', path, platform: 'desktop' },
+      response,
+      () => {},
+    );
+    response.end();
+  }
+
+  const recorded =
+    metricsService.getMetrics('http_request', { path }).count - before;
+  assert.ok(recorded >= 2 && recorded <= 3);
+});