Quickstart

// app.mjs — registered through --import ./otel.mjs, so no register import here
import { defineMeter, stop } from '@sherlock-labs/otel';
import { applyMetricsMiddleware } from '@sherlock-labs/otel/express';
import express from 'express';

const m = defineMeter('app');
const workDuration = m.histogram('app.work.duration'); // unit s, seconds buckets

const app = express();
app.use(applyMetricsMiddleware()); // app.http.server.count / .errors / .duration

app.get('/hello', (_req, res) => {
  res.json({ hello: 'world' });
});

app.get('/work', async (_req, res) => {
  const jobId = `job-${Math.round(Math.random() * 1e6)}`;
  const startedAt = performance.now();
  await new Promise((resolve) => setTimeout(resolve, 100 + Math.random() * 200));
  const seconds = (performance.now() - startedAt) / 1000;
  // 2nd argument: low-cardinality metric attributes.
  // 3rd argument: high-cardinality exemplar attributes.
  workDuration.recordWithExemplar(seconds, { kind: 'report' }, { jobId });
  res.json({ jobId, seconds });
});

const server = app.listen(3000);

process.on('SIGTERM', async () => {
  server.close();
  await stop(); // flushes the last metric interval and the pending span batch
  process.exit(0);
});