Tutorial: initializing-async-context-id-in-a-controller

In this tutorial, new the AsyncContextId and inject into the metadata, some data that down stream processes can fetch.

Latter, add the correlationId to the logs.

clear ensures no lingering data remains.

// Get the singleton instance,
const {AsyncContextId} = require('@psenger/async-context-id');
const tracker = new AsyncContextId();

async function processRequest(req, res) {
  try {
    // Set correlation ID from upstream service
    if (req.headers['x-correlation-id']) {
      tracker.setCorrelationId(req.headers['x-correlation-id']);
    }

    // Add request context
    tracker.setContext({
      metadata: {
        path: req.path,
        method: req.method,
        userAgent: req.headers['user-agent']
      }
    });

    const result = await processData(req.body);

    // Log with context
    const context = tracker.getContext();
    console.log('Request processed', {
      correlationId: context.correlationId,
      duration: Date.now() - context.startTime,
      metadata: context.metadata
    });

    res.json(result);
  } finally {
    // Clean up context
    tracker.clear();
  }
}