How to use
- Copy the installation command and review the source package before installing it in your own agent environment.
- Check the source document for required tools, credentials and supported hosts.
- Describe your input and desired deliverable; review the output against the source material.
npx skills add https://github.com/secondsky/claude-skills --skill logging-best-practicesBefore you start
- Installation does not include a model subscription, API allowance or permission to access your files.
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Original skill document
Rendered from the source repository. Headings, examples, code, tables, links, and referenced images are preserved.
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 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
