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X-ray for Express

Express integration for Stainless X-ray request logging. Provides a middleware that wraps Express requests and responses.

Install

pnpm add @stainlessdev/xray-emitter

Basic usage

import express from 'express';
import { createEmitter } from '@stainlessdev/xray-emitter/express';
import { getXrayContext } from '@stainlessdev/xray-emitter/node';

const app = express();

const xray = createEmitter({ serviceName: 'my-service' });

app.use(xray);

app.use((req, _res, next) => {
  const ctx = getXrayContext(req);
  ctx?.setActor('tenant-123', 'user-123');
  next();
});

app.get('/', (_req, res) => {
  res.send('ok');
});

The middleware also attaches the context to req.xray and res.locals.xray for convenience.

Request IDs and response headers

X-ray will auto-generate a request ID and inject it into your response headers under the configured name (requestId.header, default request-id, emitted as Request-Id) if the header is missing. If you set your own request ID first (via options.requestId or by setting the response header yourself), X-ray preserves it and does not overwrite the header.

Configuration

createEmitter(config, options?) accepts XrayRuntimeConfig (config) and WrapOptions (per-request defaults):

  • serviceName (required)
  • endpointUrl (required; falls back to STAINLESS_XRAY_ENDPOINT_URL when omitted; explicit endpointUrl wins)
  • environment, version, logger, logLevel
  • exporter: endpointUrl, headers, timeoutMs, spanProcessor, instance (custom SpanExporter)
  • capture: request/response headers and bodies
  • redaction: headers/query/body JSON-path redaction
  • requestId: header name to read/write
  • route: normalization options

Adapter options (WrapOptions)

  • route: override the route name for the request
  • requestId: explicit request ID to use (prevents auto-generation)
  • capture: per-request capture overrides
  • redaction: per-request redaction overrides
  • onRequest(ctx), onResponse(ctx, log), onError(ctx, err) hooks

Advanced usage

If you already have an XrayEmitter instance, use createExpressMiddleware(xray, options) to create middleware.

Notes

  • This package depends on OpenTelemetry packages as peer dependencies.
  • Node.js >= 20 is required.