@logbrew/express

Express middleware helpers for the public LogBrew JavaScript SDK.

This package is intentionally thin. It adds request and error middleware UX while keeping event validation, retry, flush, and shutdown behavior in @logbrew/sdk.

Install

npm install @logbrew/sdk @logbrew/express express
pnpm add @logbrew/sdk @logbrew/express express

Request Middleware

import express from "express";
import { RecordingTransport } from "@logbrew/sdk";
import { logbrewMiddleware } from "@logbrew/express";

const app = express();

app.use(logbrewMiddleware({
  serverApiKey: "LOGBREW_SERVER_API_KEY",
  transport: RecordingTransport.alwaysAccept()
}));

app.get("/health", (req, res) => {
  req.logbrew.client.log("evt_log_001", "2026-06-02T10:00:03Z", {
    message: "health check reached",
    level: "info",
    logger: "express"
  });
  res.json({ ok: true });
});

Use serverApiKey directly for local server examples, or set LOGBREW_SERVER_API_KEY in your server environment and omit it. apiKey and LOGBREW_API_KEY are still accepted for compatibility with the lower-level JavaScript SDK. Automatic request and error metadata records the path without query text by default.

When an incoming request has a valid W3C traceparent header, the default request capture records the request as a LogBrew span that continues the incoming trace. Requests without traceparent, or with a malformed header, fall back to the existing request log event so bad client headers do not break your app. Use spanIdFactory when tests or edge runtimes need deterministic child span IDs:

app.use(logbrewMiddleware({
  serverApiKey: "LOGBREW_SERVER_API_KEY",
  spanIdFactory: () => "b7ad6b7169203331",
  transport: RecordingTransport.alwaysAccept()
}));

Error Middleware

import { logbrewErrorHandler } from "@logbrew/express";

app.use(logbrewErrorHandler({
  serverApiKey: "LOGBREW_SERVER_API_KEY"
}));

app.use((err, _req, res, _next) => {
  res.status(500).json({ error: err.message });
});

Express error-handling middleware uses four arguments: (err, req, res, next). In Express 5, route handlers and middleware that return rejected promises are forwarded to error handlers automatically, so logbrewErrorHandler() is designed to capture and then pass the error onward to your existing response handler.

Packaged Examples

After install, these commands are available from a consumer app:

node node_modules/@logbrew/express/examples/index.mjs --help
node node_modules/@logbrew/express/examples/index.mjs --list
node node_modules/@logbrew/express/examples/index.mjs readme-example
node node_modules/@logbrew/express/examples/index.mjs real-user-smoke
node node_modules/@logbrew/express/examples/index.mjs
npm --prefix node_modules/@logbrew/express/examples run help
npm --prefix node_modules/@logbrew/express/examples run list
npm --prefix node_modules/@logbrew/express/examples run readme-example
npm --prefix node_modules/@logbrew/express/examples run real-user-smoke

The default launcher path runs real-user-smoke.