logging-patterns

# 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) } } } ```