Express

Express applications should configure Logfire before Express is imported, so OpenTelemetry can patch the framework and HTTP modules.

Install

Terminal

npm install express @pydantic/logfire-node dotenv

Instrumentation File

instrumentation.ts

import * as logfire from '@pydantic/logfire-node'
import 'dotenv/config'

logfire.configure({
  serviceName: 'express-api',
})

Put your token in .env:

.env

LOGFIRE_TOKEN=your-write-token

App Code

app.ts

import express from 'express'
import * as logfire from '@pydantic/logfire-node'

const app = express()

app.get('/rolldice', (_req, res) => {
  logfire.info('rolling dice')
  res.send(String(Math.floor(Math.random() * 6) + 1))
})

app.use((err: Error, _req: express.Request, res: express.Response, _next: () => unknown) => {
  logfire.reportError('express request failed', err)
  res.status(500).send('internal server error')
})

app.listen(8080)

Run with the instrumentation file loaded first:

Terminal

node --import ./instrumentation.js app.js

For a complete project, see examples/express.