# Logging Patterns

> Common logging patterns and practices. This skill is designed to be included in composite skills via the 'includes' feature.

- Skill: `majiayu000/logging-patterns` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/logging-patterns`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/logging-patterns/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/logging-patterns

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# Logging Patterns

Foundational logging practices for observable applications.

## Rules

- Use structured logging (key-value pairs, not interpolated strings)
- Include request/correlation IDs in all log entries
- Log at appropriate levels (DEBUG, INFO, WARN, ERROR)
- Include enough context to debug issues without the code
- Don't log sensitive information (passwords, tokens, PII)

## Pitfalls

- Logging sensitive data (passwords, API keys, PII)
- Inconsistent log levels across the codebase
- Missing correlation IDs in distributed systems
- Logging at wrong levels (DEBUG in prod, ERROR for non-errors)

## Examples

```rust
// Structured logging with tracing
use tracing::{info, error, instrument};

#[instrument(skip(password))]
fn authenticate(user_id: &str, password: &str) -> Result<Token> {
    info!(user_id, "authentication attempt");

    match verify_credentials(user_id, password) {
        Ok(token) => {
            info!(user_id, "authentication successful");
            Ok(token)
        }
        Err(e) => {
            error!(user_id, error = %e, "authentication failed");
            Err(e)
        }
    }
}
```