Correlation IDs

Correlation ID Flow

Client Request
    │
    â–¼ X-Request-ID: req-abc-123
┌────────────────┐
│ API Gateway    │──▶ Log: req-abc-123 received
└───────┬────────┘
        │
        â–¼ X-Request-ID: req-abc-123
┌────────────────┐
│ Order Service  │──▶ Log: req-abc-123 processing order
└───────┬────────┘
        │
        â–¼ X-Request-ID: req-abc-123
┌────────────────┐
│ Payment Svc    │──▶ Log: req-abc-123 charging payment
└────────────────┘

All logs correlated by req-abc-123

Magento Correlation ID Middleware

class CorrelationIdPlugin {
    public function beforeExecute(
        $subject,
        RequestInterface $request
    ) {
        $requestId = $request->getHeader('X-Request-ID')
            ?? $this->generateRequestId();

        // Store in registry for logging
        $registry = $this->registry;
        $registry->register('request_id', $requestId);

        // Add to response header
        $this->responseHeader->addHeader(
            'X-Request-ID', $requestId
        );

        // Set in MDC for log context
        $this->logger->pushProcessor(function ($record) use ($requestId) {
            $record['extra']['request_id'] = $requestId;
            return $record;
        });
    }

    private function generateRequestId(): string {
        return 'req-' . bin2hex(random_bytes(8));
    }
}

HTTP Header Propagation

// Forward correlation ID to downstream services
function callExternalService($url, $data) {
    $requestId = $this->registry->registry('request_id');

    $response = $this->httpClient->post($url, [
        'headers' => [
            'X-Request-ID' => $requestId,
            'X-Forwarded-For' => $_SERVER['REMOTE_ADDR']
        ],
        'json' => $data
    ]);

    return $response;
}

W3C Trace Context

Header: traceparent
Format: 00-TRACE_ID-SPAN_ID-FLAGS

Example:
00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01
│   │                        │                │    │
│   │                        │                │    └─ Flags
│   │                        │                └────── Parent span ID
│   │                        └─────────────────────── Span ID
│   └───────────────────────────────────────────────── Trace ID
└───────────────────────────────────────────────────── Version

Magento Trace Context Plugin

class TraceContextPlugin {
    public function beforeExecute(
        $subject,
        RequestInterface $request
    ) {
        $traceparent = $request->getHeader('traceparent');

        if ($traceparent) {
            // Parse and store trace context
            $parts = explode('-', $traceparent);
            $this->registry->register('trace_id', $parts[1]);
            $this->registry->register('span_id', $parts[2]);
        } else {
            // Generate new trace context
            $traceId = bin2hex(random_bytes(16));
            $spanId = bin2hex(random_bytes(8));
            $this->registry->register('trace_id', $traceId);
            $this->registry->register('span_id', $spanId);
        }
    }
}

Trace Context in Logs

// Include trace context in all logs
$logger->pushProcessor(function ($record) {
    $record['extra']['trace_id'] = $this->registry->registry('trace_id');
    $record['extra']['span_id'] = $this->registry->registry('span_id');
    return $record;
});

// Log output includes trace context
// {"trace_id": "4bf92f35...", "span_id": "00f067aa...", "message": "..."}

Debugging Workflow

1. Customer reports issue
2. Get request ID from response header
3. Query logs by request ID
4. See full request flow across services
5. Identify failure point

Log Query Examples

# Kibana query
request_id: "req-abc-123"

# Elasticsearch API
GET /magento-logs-*/_search
{
  "query": {
    "term": { "request_id": "req-abc-123" }
  },
  "sort": [{ "timestamp": "asc" }]
}

# Results show complete request lifecycle:
# 10:30:00 INFO  - API Gateway: Received request
# 10:30:01 INFO  - Order Service: Processing order 12345
# 10:30:01 DEBUG - Order Service: SQL query executed (15ms)
# 10:30:02 INFO  - Payment Service: Charging $99.99
# 10:30:03 ERROR - Payment Service: Gateway timeout
# 10:30:03 INFO  - Order Service: Retrying payment
# 10:30:04 INFO  - Payment Service: Payment successful

Debug Endpoints

// Debug endpoint for support team
if ($request->getParam('debug') && $this->auth->isAdmin()) {
    return [
        'request_id' => $this->registry->registry('request_id'),
        'trace_id' => $this->registry->registry('trace_id'),
        'service' => 'magento',
        'environment' => getenv('APP_ENV'),
        'server' => gethostname()
    ];
}

OpenTelemetry Correlation

use OpenTelemetry\Context\Context;
use OpenTelemetry\Context\Propagation\TraceContextPropagator;

// Inject trace context into outgoing requests
$propagator = new TraceContextPropagator();
$context = Context::getCurrent();

$headers = [];
$propagator->inject($headers, $context);

// $headers now contains traceparent header
$httpClient->post($url, ['headers' => $headers]);

Jaeger Integration

// Send trace data to Jaeger
$tracer = new JaegerTracer('magento', 'http://jaeger:14268/api/traces');

$span = $tracer->startSpan('process_order');
$span->setTag('order.id', $orderId);
$span->log(['event' => 'payment_started']);

try {
    $this->paymentService->charge($order);
    $span->setTag('payment.status', 'success');
} catch (Exception $e) {
    $span->setTag('error', true);
    $span->log(['event' => 'payment_failed', 'error' => $e->getMessage()]);
} finally {
    $span->finish();
}