Express

The AppSignal for Node.js integration for Express.js (express) v4.0.0+.

Installation

Add both the @appsignal/nodejs and @appsignal/express packages to your package.json. Then, run yarn install/npm install.

You can also add these packages to your package.json on the command line:

yarn add @appsignal/nodejs @appsignal/express
npm install --save @appsignal/nodejs @appsignal/express

You can then import and use the package in your app.

Usage

Middleware

The module includes middleware for automatically instrumenting the routes of your application. The order in which things are imported and used in your application is important, so be sure to note where things are required/imported in the examples below.

Don't forget - to auto-instrument modules (including Node.js' internal http module, used by express), the Appsignal module must be both required and initialized before any other package.

// AT THE VERY TOP OF THE ENTRYPOINT OF YOUR APPLICATION...
const { Appsignal } = require("@appsignal/nodejs");
 
const appsignal = new Appsignal({
  active: true,
  name: "<YOUR APPLICATION NAME>",
  pushApiKey: "<YOUR API KEY>", // Note: renamed from `apiKey` in version 2.2.5
});
 
// ...ALL THE REST OF YOUR IMPORTS AND CODE GO HERE!
 
const express = require("express");
const { expressMiddleware } = require("@appsignal/express");
 
const app = express();
 
// ADD THIS AFTER ANY OTHER EXPRESS MIDDLEWARE, BUT BEFORE ANY ROUTES!
app.use(expressMiddleware(appsignal));

Error Handler

The module also contains a middleware for catching any errors passed to next().

// AT THE VERY TOP OF THE ENTRYPOINT OF YOUR APPLICATION...
const { Appsignal } = require("@appsignal/nodejs");
 
const appsignal = new Appsignal({
  active: true,
  name: "<YOUR APPLICATION NAME>",
  pushApiKey: "<YOUR API KEY>", // Note: renamed from `apiKey` in version 2.2.5
});
 
// ...ALL THE REST OF YOUR IMPORTS AND CODE GO HERE!
 
const express = require("express");
const { expressErrorHandler } = require("@appsignal/express");
 
const app = express();
 
// ADD THIS AFTER ANY OTHER EXPRESS MIDDLEWARE, AND AFTER ANY ROUTES!
app.use(expressErrorHandler(appsignal));

Only exceptions with status code 500 and above will be reported to AppSignal automatically. To send exceptions to AppSignal with other status codes, you can use custom exception handling.

Example app

An example Express app, containing usage of all of our middleware and custom instrumentation can be found here.