logging-observabilitylisted

# Logging & Observability Skill Activate when working with logging systems, distributed tracing, debugging, monitoring, or any observability-related tasks across applications. ## 1. Logging Best Practices ### Log Levels Use appropriate log levels for different severity: | Level | Severity | When to Use | |-------|----------|------------| | **DEBUG** | Low | Development only - detailed info, variable states, control flow. Use sparingly in production. | | **INFO** | Low | Important application lifecycle events - startup, shutdown, config loaded, user actions, key state changes. | | **WARN** | Medium | Recoverable issues - deprecated usage, resource constraints, unexpected but handled conditions. Investigate later. | | **ERROR** | High | Unrecoverable problems - exceptions, failed operations, missing required data. Requires immediate attention. | | **FATAL** | Critical | System-level failures - abort conditions, out of memory, unrecoverable state. System may crash. | ### General Principles - **Actionable**: Logs should help diagnose problems, not just record events - **Contextual**: Include enough context to understand what happened without code inspection - **Consistent**: Use same terminology across codebase for same events - **Sparse**: Don't log everything - unnecessary noise obscures real issues - **Sampling**: In high-volume scenarios, sample logs (10%, 1%, etc.) rather than logging everything - **Structured**: Always use structured format (JSON) for programmatic pa