backend/src/modules/metrics/index.ts

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'>;
  providerMetrics: Counter<
    | 'title'
    | 'tmdb_id'
    | 'season_id'
    | 'episode_id'
    | 'status'
    | 'type'
    | 'provider_id'
    | 'embed_id'
    | 'hostname'
  >;
};

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',
    routeMetrics: {
      enabled: true,
      registeredRoutesOnly: true,
    },
  });

  metrics = {
    user: new Counter({
      name: 'user_count',
      help: 'user_help',
      labelNames: ['namespace'],
    }),
    providerMetrics: new Counter({
      name: 'provider_metrics',
      help: 'provider_metrics',
      labelNames: [
        'episode_id',
        'provider_id',
        'season_id',
        'status',
        'title',
        'tmdb_id',
        'type',
        'embed_id',
        'hostname',
      ],
    }),
  };

  const promClient = app.metrics.client;

  promClient.register.registerMetric(metrics.user);
  promClient.register.registerMetric(metrics.providerMetrics);

  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' });
}