Logging Best Practices

Logging Best Practices Skill

Version: 1.0.0

Purpose

This skill provides guidelines for implementing effective logging in applications. It focuses on wide events (also called canonical log lines) - a pattern where you emit a single, context-rich event per request per service, enabling powerful debugging and analytics.

When to Apply

Apply these guidelines when:

• Writing or reviewing logging code
• Adding console.log, logger.info, or similar
• Designing logging strategy for new services
• Setting up logging infrastructure

Core Principles

1. Wide Events (CRITICAL)

Emit one context-rich event per request per service. Instead of scattering log lines throughout your handler, consolidate everything into a single structured event emitted at request completion.

const wideEvent: Record<string, unknown> = {
  method: 'POST',
  path: '/checkout',
  requestId: c.get('requestId'),
  timestamp: new Date().toISOString(),
};

try {
  const user = await getUser(c.get('userId'));
  wideEvent.user = { id: user.id, subscription: user.subscription };