Classification of Logging
- Gopal Sharma
Categorizing logs into different levels and classes helps you manage them better. You can adjust logging verbosity based on the environment (e.g., development, staging, production) and application needs. A detailed classification of logging will help the team better understand the type of data they should log and how to structure it based on the severity and relevance. Here’s a refined approach to the Classification of Logging, broken down into different categories, with concrete examples for each:
1. Debug Logs (DEBUG)
Purpose: Detailed information for developers to diagnose issues. These logs provide deep insights into the internal state of the application. They are usually verbose and are not needed in production unless troubleshooting specific issues.
Example Use Case: During development or debugging, to track variable states or function calls.
Example:
logger.debug("Entering method processPayment() with transaction ID: {}", transactionId);
logger.debug("Processing payment for user {} with amount: {}", userId, paymentAmount);
When to Enable: Only in development or troubleshooting environments.
When to Disable: Should be disabled or set to log less frequently in production environments to save on costs.
2. Informational Logs (INFO)
Purpose: Logs key application events and milestones to provide a high-level overview of the system’s operation. These logs should not be excessively verbose and can help to track system behavior during normal operations. Typically used to track regular activities like service startups, API calls, or successful transactions.
Example Use Case: System start-up, database connections, or an important event completion.
Example:
logger.info("User {} successfully logged in at {}", userId, loginTimestamp);
logger.info("Service started successfully on port 8080");
When to Enable: Enabled in production but should be moderate. Track major events, system health, and high-level user actions.
When to Disable: Do not use for routine actions that don't add value, or it will flood the logs.
3. Warning Logs (WARN)
Purpose: Logs situations that are not errors but could indicate potential issues that might require attention in the future. Warnings may not immediately disrupt service but should be reviewed to avoid problems down the road. These logs help to identify suboptimal or deprecated behavior, and impending failure points.
Example Use Case: API rate limits approaching, deprecated feature usage, or insufficient disk space.
Example:
logger.warn("User {} is attempting to access a deprecated API endpoint", userId);
logger.warn("Memory usage is at 90%, consider scaling the service");
When to Enable: Enabled in production for events that require attention but are not critical.
When to Disable: Only log warnings for significant issues, not every minor inefficiency or issue.
4. Error Logs (ERROR)
Purpose: Logs actual issues that disrupt the system’s operation but are recoverable. These logs are useful for identifying and addressing issues that affect user experience, system reliability, or functionality. Critical errors that affect a single transaction or request often go here.
Example Use Case: Failed transactions, unhandled exceptions, or failed database connections.
Example:
logger.error("Failed to process payment for user {} due to database timeout", userId);
logger.error("Service failed to connect to database, retrying in 10 seconds");
When to Enable: Always enabled in production. Errors that affect users or system reliability should be logged at this level.
When to Disable: Should never disable logging for errors unless you're filtering out minor issues that are known and non-impactful.
5. Critical Logs (FATAL / CRITICAL)
Purpose: Logs critical failures that lead to the application being unusable or crashing. These are the most severe errors, indicating that the application is likely in an inconsistent or non-operational state. Critical logs are usually used to indicate system crashes, out-of-memory errors, or unhandled exceptions that require immediate attention.
Example Use Case: Application crashes, fatal unhandled exceptions, system resource exhaustion, or a total failure in a critical dependency (e.g., database down).
Example:
logger.fatal("System crash: Out of memory, unable to allocate more resources");
logger.fatal("Critical error: Database service is down, application shutting down");
When to Enable: Always enabled in production for catastrophic failures.
When to Disable: These logs should not be disabled; they are meant to alert teams to the most severe issues that need immediate resolution.
6. Security and Audit Logs
Purpose: Logs related to security events, user actions, and changes to sensitive data or systems. These are essential for ensuring regulatory compliance and security monitoring. Audit logs help track changes to system configurations, user roles, access attempts, and more.
Example Use Case: User authentication attempts, password changes, privilege escalation, or access to sensitive data.
Example:
logger.info("User {} attempted to access sensitive data at {}", userId, timestamp);
logger.audit("User {} changed their password", userId);
When to Enable: Always enabled, particularly in production, for security-critical systems or compliance-related environments.
When to Disable: Never disable these logs unless they are non-sensitive and are not relevant to security or audit requirements.
7. Performance Monitoring Logs
Purpose: Logs that track the performance of the application or system. These logs are particularly useful for identifying bottlenecks and ensuring optimal performance. Logs might include database query performance, response time of external services, or processing times for user requests.
Example Use Case: Tracking API response times, database query durations, or memory usage statistics.
Example:
logger.info("API response time for getUserDetails API: {} ms", responseTime);
logger.info("Database query took {} ms to execute", queryExecutionTime);
When to Enable: Production (but selectively), as performance data can be useful to monitor and optimize the system.
When to Disable: Disable excessive logging of performance metrics if the overhead is too large or if it doesn't contribute to troubleshooting.
8. External Service Interaction Logs
Purpose: Logs of interactions with external systems (e.g., third-party services, APIs, or microservices). These logs are crucial for understanding the behavior of interactions across service boundaries and troubleshooting external service failures.
Example Use Case: Calls to a payment gateway, external APIs, or microservices.
Example:
logger.info("Calling payment gateway with amount: {} for user {}", amount, userId);
logger.error("Payment gateway failed to respond for user {} with error: {}", userId, errorMessage);
When to Enable: Always enabled in production for tracking external service failures or timeouts.
When to Disable: Shouldn’t be disabled, but avoid excessive verbosity unless you need detailed traces for debugging.
9. Health Checks and Service Status Logs
Purpose: Logs related to the health status of your application or its components. These logs can track whether services are up, the health of dependencies (databases, caches), and if any components are degrading or failing.
Example Use Case: Regular health checks to ensure the application’s major components are functioning correctly.
Example:
logger.info("Health check passed: Database connection is healthy");
logger.warn("Service xyz is experiencing high response latency, health check failed");
When to Enable: Always enabled in production for operational visibility and uptime monitoring.
When to Disable: Don't disable these logs, as they help in proactively monitoring system health.
Summary of Key Points for Each Log Type
Log Level | Description | When to Use | When to Disable |
|---|---|---|---|
DEBUG | Detailed developer logs for diagnosing issues. | During development and debugging. | Never in production unless needed. |
INFO | High-level, important application events. | Enabled in production for key events. | Avoid excessive info logs in production. |
WARN | Indicates potential problems or non-critical failures. | Use in production for warnings. | Avoid for non-significant issues. |
ERROR | Logs actual failures or issues that need attention. | Always enabled in production. | Never disable for critical issues. |
CRITICAL/FATAL | Logs catastrophic failures that require immediate attention. | Always enabled in production. | Should never be disabled. |
Security/Audit | Logs sensitive events related to security and user actions. | Always enabled in compliance contexts. | Never disable in production. |
Performance | Logs tracking system performance (e.g., response times). | Enable for performance monitoring. | Avoid excessive performance logs. |
External Services | Logs interactions with external systems and APIs. | Always enable for tracking external service interactions. | Avoid verbose logs for every interaction. |
Health Checks | Logs related to service health and operational status. | Enable for production monitoring. | Never disable for health checks. |
This approach ensures that logs are categorized appropriately and enables efficient log management. It not only helps to control the costs but also improves the quality of the data collected for debugging and monitoring purposes.