Logging Best Practices Skill for Claude

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.

2k tokens

context cost

the whole folder, loaded on every use

files

instructions only

copies elsewhere

how many repositories repackaged it

202

stars on the repo

on the repository, not the skill itself

Install

one command, takes just this skill from the repository

npx skills add https://github.com/secondsky/claude-skills --skill logging-best-practices

The instruction itself

8 sections, as written by the author

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)

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

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

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 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

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How to use it

Copy the folder

Take secondsky/logging-best-practices from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

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