Datadog Middleware for Express/Connect

Common errors

Warnings

Install

Imports

• connectDatadog
  wrong

  import connectDatadog from 'connect-datadog'; // ESM not supported

  correct

  const connectDatadog = require('connect-datadog');
  app.use(connectDatadog({}));

  This package is CommonJS-only and does not support ES module imports. The `require` call itself returns the middleware function.

• DatadogOptions
  wrong

  import { DatadogOptions } from 'connect-datadog'; // No types, no named exports

  correct

  const connectDatadog = require('connect-datadog');
  const ddOptions = {
    stat: 'web.requests',
    tags: ['env:production'],
    response_code: true
  };
  app.use(connectDatadog(ddOptions));

  Configuration is passed as an object to the middleware function. There are no exposed types for TypeScript users, nor are there named exports.

• StatsDClientOverride
  wrong

  const customDogstatsdClient = new SomeOtherClient(); // Must be node-dogstatsd compatible

  correct

  const connectDatadog = require('connect-datadog');
  const StatsD = require('node-dogstatsd').StatsD;
  const customDogstatsdClient = new StatsD({ host: '127.0.0.1', port: 8125 });
  app.use(connectDatadog({ dogstatsd: customDogstatsdClient }));

  The `dogstatsd` option expects an instance of a `node-dogstatsd` compatible client. Using a different StatsD client might lead to unexpected behavior or errors.

Quickstart

Demonstrates integrating the `connect-datadog` middleware into a basic Express application to send HTTP request metrics to a Datadog Agent.

const express = require('express');
const connectDatadog = require('connect-datadog');
const app = express();
const port = process.env.PORT || 3000;

// Datadog middleware options
const ddOptions = {
  stat: 'node.express.router',
  tags: ['app:my-old-express-app', 'environment:development'],
  path: true, // Include path tag
  method: true, // Include http method tag
  response_code: true // Include http response code tag
};

// Add middleware immediately before your router, as per original instructions.
// NOTE: The example `app.use(app.router)` is deprecated in modern Express.
// Instead, place this middleware before your route definitions.
app.use(connectDatadog(ddOptions));

app.get('/', (req, res) => {
  res.send('Hello from Datadog-monitored Express App!');
});

app.get('/data', (req, res) => {
  res.json({ message: 'Some data' });
});

app.listen(port, () => {
  console.log(`Server listening at http://localhost:${port}`);
  console.log('Ensure Datadog Agent with DogStatsD is running on the host.');
});