Skip to content
Trailscope

Express: @trailscope/express

Request logging, error capture and context for Express 4 and 5. Built on @trailscope/node; shared behaviour is in sdk-spec.md.

Terminal window
npm install @trailscope/express
import express from 'express';
import { init, trailscope, trailscopeErrorHandler, setCorrelation, setUser } from '@trailscope/express';


init({ service: 'orders-api' });     // TRAILSCOPE_INGEST_KEY from the environment


const app = express();
app.use(trailscope());                   // first, so it times everything
app.use(express.json());
app.get('/orders/:id', (req, res) => {
  setCorrelation('order_id', req.params.id);
  res.json(loadOrder(req.params.id));
});
app.use(trailscopeErrorHandler());       // after the routes, before your own error handlers
  • trailscope(clientOrOptions?) is the middleware. Pass a TrailscopeClient, or options to create the process-wide client. Without arguments it uses the client from init(), or creates one from the TRAILSCOPE_* variables.
  • trailscopeErrorHandler() records the error (type, message and stack, kept when the response is a 5xx) and passes it on with next(err), so your own error handlers still answer.
  • Routes are recorded as Express defines them: req.baseUrl + req.route.path, so a router mounted at /orders with /:id gives /orders/:id.
  • The request body is the parsed req.body, so register body parsers as usual; the response body is copied as it is written.
  • The client IP is req.ip, which follows Express’s trust proxy setting.
  • Call setUser() in your authentication middleware, and setCorrelation() wherever a journey key (an order, an account, a session) is known.

Everything from @trailscope/node used in request handlers is re-exported: init, getClient, TrailscopeClient, setUser, setCorrelation, setAttribute, recordError, currentContext, contextOf.

A runnable app is in examples/express.