Understanding walkerOS Sources

Overview

Sources capture events from the external world (browser DOM, dataLayer, HTTP requests, cloud functions) and feed them to the collector.

Core principle: Sources capture. They don't process or deliver—that's collector and destinations.

Source Interface

See packages/core/src/types/source.ts for canonical interface.

Init Function (Context Pattern)

Sources use a context-based initialization pattern:

import type { Source } from '@walkeros/core';

export const sourceMySource: Source.Init<Types> = async (context) => {
  const { config = {}, env, logger, id } = context;
  // ...
};

Context contains:

Push Method

Push Signatures by Type

Key insight: Source push IS the handler. No wrappers needed.

// Direct deployment
http('handler', source.push);

Source Paths

Browser Source

The browser source captures events from DOM using data attributes.

<button data-elb="product" data-elb-product="id:P123;name:Laptop">
  <span data-elbaction="click">Add to Cart</span>
</button>

See packages/web/sources/browser/ for implementation.

DataLayer Source

Captures events from a GTM-style dataLayer array.

window.dataLayer.push({
  event: 'product view',
  product: { id: 'P123', name: 'Laptop' },
});

See packages/web/sources/dataLayer/ for implementation.

Server Sources

Handle HTTP requests in cloud functions. Server sources use the context pattern:

import type { Source } from '@walkeros/core';

export const sourceCloudFunction: Source.Init<Types> = async (context) => {
  const { config = {}, env } = context;
  const { push: envPush } = env;

  // Validate settings with Zod schema
  const settings = SettingsSchema.parse(config.settings || {});

  const push = async (req: Request, res: Response): Promise<void> => {
    // Transform HTTP request → walkerOS event
    const event = transformRequest(req);
    await envPush(event);
    res.json({ success: true });
  };

  return { type: 'cloudfunction', config: { ...config, settings }, push };
};

// Direct deployment
export const handler = source.push;

See packages/server/sources/gcp/ for implementation.

Transformer Wiring

Sources can wire to pre-collector transformer chains via the next property:

sources: {
  browser: {
    code: sourceBrowser,
    next: 'validate'  // First transformer to run after this source
  }
}

The transformer chain runs before events reach the collector. See understanding-transformers for chain details.

Related Skills

• walkeros-understanding-flow - How sources fit in architecture
• walkeros-understanding-events - Events that sources emit
• walkeros-create-source - Create new source

Source Files:

• packages/core/src/types/source.ts - Interface

Package READMEs:

• packages/web/sources/browser/README.md - Browser source
• packages/web/sources/dataLayer/README.md - DataLayer source

Documentation:

• Website: Sources - Overview
• Website: Browser Source - Browser docs
• Website: Create Your Own - Guide