Express
Turn-key HTTP event collection server with Express.js. Handles JSON POST events, pixel tracking (GET), and CORS.
Features
- Standalone or embedded: Start server automatically or integrate with existing Express app
- CORS support: Configurable cross-origin resource sharing
- Pixel tracking: 1x1 transparent GIF for GET requests
The Express Source is a server source in the walkerOS flow:
It receives events via HTTP (POST/GET) and forwards them to configured destinations.
Installation
The path setting has been renamed to paths (array). The old path still works but is deprecated and will be removed in the next major version.
// Before (deprecated)
settings: { path: '/events' }
// After
settings: { paths: ['/events'] }
Quick start
- Integrated
- Bundled
Add to your flow.json sources:
Server sources require platform-specific handlers. For containerized deployments, see Docker →.
Configuration
| Property | Type | Description | More |
|---|---|---|---|
port | integer | HTTP server port to listen on. Use 0 for random available port. If not provided, server will not start (app only mode) | |
path | string | Deprecated: use paths instead | |
paths | Array<any> | Route paths to register. String shorthand registers GET+POST. RouteConfig allows per-route method control. | |
cors | boolean | object | CORS configuration: false = disabled, true = allow all origins (default), object = custom configuration |
HTTP methods
| Method | Endpoint | Description |
|---|---|---|
| POST | /collect | JSON event ingestion |
| GET | /collect | Pixel tracking (returns 1x1 GIF) |
| OPTIONS | /collect | CORS preflight |
Health check endpoints (/health and /ready) are provided by the runner, not by individual sources. This means health checks work regardless of which source type you use.
Ingest Metadata
Extract request metadata (IP, user agent, headers) and forward it through the pipeline to transformers and destinations.
Available Ingest Paths
| Path | Description |
|---|---|
ip | Client IP address |
headers.* | HTTP headers (user-agent, origin, referer, etc.) |
protocol | Request protocol (http/https) |
method | HTTP method (GET, POST, etc.) |
hostname | Request hostname |
url | Full request URL |
Advanced Mapping
Use walkerOS mapping features for complex extraction: