added user metrics

src/modules/metrics/index.ts

@@ -0,0 +1,39 @@
+import { getORM } from '@/modules/mikro';
+import { FastifyInstance } from 'fastify';
+import { Counter } from 'prom-client';
+import metricsPlugin from 'fastify-metrics';
+import { updateMetrics } from '@/modules/metrics/update';
+import { scopedLogger } from '@/services/logger';
+
+const log = scopedLogger('metrics');
+
+export type Metrics = {
+  user: Counter<'namespace'>;
+};
+
+let metrics: null | Metrics = null;
+
+export function getMetrics() {
+  if (!metrics) throw new Error('metrics not initialized');
+  return metrics;
+}
+
+export async function setupMetrics(app: FastifyInstance) {
+  log.info(`Setting up metrics...`, { evt: 'start' });
+
+  await app.register(metricsPlugin, { endpoint: '/metrics' });
+
+  metrics = {
+    user: new Counter({
+      name: 'user_count',
+      help: 'user_help',
+      labelNames: ['namespace'],
+    }),
+  };
+
+  const orm = getORM();
+  const em = orm.em.fork();
+  log.info(`Syncing up metrics...`, { evt: 'sync' });
+  await updateMetrics(em, metrics);
+  log.info(`Metrics initialized!`, { evt: 'end' });
+}

src/modules/metrics/update.ts

@@ -0,0 +1,22 @@
+import { User } from '@/db/models/User';
+import { Metrics } from '@/modules/metrics';
+import { EntityManager } from '@mikro-orm/postgresql';
+
+export async function updateMetrics(em: EntityManager, metrics: Metrics) {
+  const users = await em
+    .createQueryBuilder(User)
+    .groupBy('namespace')
+    .count()
+    .select(['namespace', 'count'])
+    .execute<
+      {
+        namespace: string;
+        count: string;
+      }[]
+    >();
+
+  metrics.user.reset();
+  users.forEach((v) => {
+    metrics?.user.inc({ namespace: v.namespace }, Number(v.count));
+  });
+}