Correlation IDs — Tracing Requests Across Microservices with Correlation IDs

// Correlation ID middleware
const { v4: uuidv4 } = require('uuid');

function correlationIdMiddleware(req, res, next) {
  const correlationId = req.headers['x-correlation-id'] || uuidv4();
  req.correlationId = correlationId;
  res.setHeader('x-correlation-id', correlationId);
  next();
}

// Propagation to downstream services
async function callDownstreamService(req, url, body) {
  return axios.post(url, body, {
    headers: {
      'x-correlation-id': req.correlationId,
      'x-span-id': uuidv4(),
      'x-parent-span-id': req.spanId
    }
  });
}

// Structured log with correlation
logger.info({
  message: 'Scan initiated',
  correlationId: req.correlationId,
  spanId: req.spanId,
  scanId: scan.id,
  duration: 0
});

// Async context for automatic correlation
const { AsyncLocalStorage } = require('async_hooks');
const asyncContext = new AsyncLocalStorage();

function contextMiddleware(req, res, next) {
  asyncContext.run({
    correlationId: req.correlationId,
    userId: req.user?.id,
    startTime: Date.now()
  }, () => next());
}

function getContext() {
  return asyncContext.getStore();
}

// Logger with automatic context injection
const contextualLogger = {
  info: (msg, data) => {
    const ctx = getContext();
    logger.info({ ...ctx, message: msg, ...data });
  }
};