---
name: logging-best-practices-ab282bca7379
description: Structured logging with proper levels, context, PII handling, centralized aggregation. Use for application logging, log management integration, distributed tracing, or encountering log bloat, PII exposure, missing context errors.
license: MIT
---

# Logging Best Practices

Implement secure, structured logging with proper levels and context.

## Log Levels

| Level | Use For | Production |
|-------|---------|------------|
| DEBUG | Detailed debugging | Off |
| INFO | Normal operations | On |
| WARN | Potential issues | On |
| ERROR | Errors with recovery | On |
| FATAL | Critical failures | On |

## Structured Logging (Winston)

```javascript
const winston = require('winston');

const logger = winston.createLogger({
  level: process.env.LOG_LEVEL || 'info',
  format: winston.format.combine(
    winston.format.timestamp(),
    winston.format.json()
  ),
  defaultMeta: { service: 'api-service' },
  transports: [
    new winston.transports.Console(),
    new winston.transports.File({ filename: 'error.log', level: 'error' })
  ]
});

// Usage
logger.info('User logged in', { userId: '123', ip: '192.168.1.1' });
logger.error('Payment failed', { error: err.message, orderId: '456' });
```

## Request Context

```javascript
const { AsyncLocalStorage } = require('async_hooks');
const storage = new AsyncLocalStorage();

app.use((req, res, next) => {
  const context = {
    requestId: req.headers['x-request-id'] || uuid(),
    userId: req.user?.id
  };
  storage.run(context, next);
});

function log(level, message, meta = {}) {
  const context = storage.getStore() || {};
  logger.log(level, message, { ...context, ...meta });
}
```

## PII Sanitization

```javascript
const sensitiveFields = ['password', 'ssn', 'creditCard', 'token'];

function sanitize(obj) {
  const sanitized = { ...obj };
  for (const field of sensitiveFields) {
    if (sanitized[field]) sanitized[field] = '[REDACTED]';
  }
  if (sanitized.email) {
    sanitized.email = sanitized.email.replace(/(.{2}).*@/, '$1***@');
  }
  return sanitized;
}
```

## Best Practices

- Use structured JSON format
- Include correlation IDs across services
- Sanitize all PII before logging
- Use async logging for performance
- Implement log rotation
- Never log at DEBUG in production

## Additional Implementations

See [references/advanced-logging.md](references/advanced-logging.md) for:
- Python structlog setup
- Go zap high-performance logging
- ELK Stack integration
- AWS CloudWatch configuration
- OpenTelemetry tracing

## Never Do

- Log passwords or tokens
- Use console.log in production
- Log inside tight loops
- Include stack traces for client errors


---
Source attribution: secondsky
Original project: https://github.com/secondsky/claude-skills/blob/88378361314f558fb719aec0af9fd898ab36f0b2/plugins/logging-best-practices/skills/logging-best-practices/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Copyright (c) 2025 Claude Skills Maintainers

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Mega AI Hub resource metadata

Creator / publisher: secondsky
Original project: https://github.com/secondsky/claude-skills/blob/88378361314f558fb719aec0af9fd898ab36f0b2/plugins/logging-best-practices/skills/logging-best-practices/SKILL.md
Attribution basis: Source repository record

Fields of work: Development & Engineering
Roles: Backend Developer, Data Engineer, DevOps / SRE
Specialties: API, Backend, Word Documents, Frontend, Stripe
Tools: Opentelemetry, Winston
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: d86b573fe311d73502697b6a5a4da31a11ff3824c0623b06389e9a113fab8a98