What is Logging?
Logging is the practice of recording events, messages, and data generated by applications, systems, and infrastructure. Logs provide visibility into system behavior, support debugging, enable security monitoring, and fulfill compliance requirements.
Log Types
Application Logs
- Error messages
- Debug information
- Business events
- Performance metrics
System Logs
- OS events
- Hardware status
- Resource usage
Security Logs
- Authentication events
- Access attempts
- Security alerts
Audit Logs
- User actions
- Data changes
- Compliance events
Log Levels
| Level | Purpose |
|---|---|
| TRACE | Detailed debugging |
| DEBUG | Development debugging |
| INFO | Informational |
| WARN | Potential issues |
| ERROR | Error conditions |
| FATAL | Critical failures |
Log Management
Collection
- Application instrumentation
- Agent-based collection
- Syslog forwarding
Aggregation
- Centralized storage
- Log shipping
- Stream processing
Analysis
- Search and query
- Pattern detection
- Visualization
Best Practices
What to Log
- Timestamps (ISO 8601)
- Correlation IDs
- User/session identifiers
- Request/response info
- Error details
What NOT to Log
- Passwords
- API keys
- PII (or mask it)
- Sensitive business data
Tools
- ELK Stack (Elasticsearch)
- Splunk
- Datadog
- CloudWatch
- Grafana Loki