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intermediate Phase · Observability

Logging

Implement structured, leveled logging for backend applications.

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Logging

Logging Frameworks

Framework Description
SLF4J API (facade)
Logback Implementation (Spring default)
Log4j2 Implementation (fast)

Log Levels

TRACE < DEBUG < INFO < WARN < ERROR

SLF4J Usage

@Slf4j
public class MyService {
    public void process() {
        log.debug("Processing item {}", itemId);
        try {
            // processing
        } catch (Exception e) {
            log.error("Failed to process item {}", itemId, e);
        }
    }
}

Logging Best Practices

Levels

TRACE < DEBUG < INFO < WARN < ERROR < FATAL

Structured Logging

{
  "timestamp": "...",
  "level": "INFO",
  "message": "...",
  "requestId": "..."
}

Best Practices

  • Use SLF4J facade
  • Include correlation IDs
  • Don't log sensitive data
  • Use appropriate levels

Key Points

  • Understanding Logging Deep Dive is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0 / 3 solved
Implement Logging Deep Dive

Design and implement a solution for Logging Deep Dive in a backend system. Consider scalability, error handling, and production readiness.

Solution 
// Logging Deep Dive implementation
// Key aspects: validation, error handling, logging, testing

public class LoggingDeepDive {
    // Production-ready implementation
}
Logging Deep Dive Edge Cases

Identify and handle edge cases for Logging Deep Dive. What happens under high load, with invalid input, or during failures?

Solution 
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotency
Logging Deep Dive Testing Strategy

Write a testing strategy for Logging Deep Dive. Include unit tests, integration tests, and performance tests.

Solution 
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. Spring Boot default logging?

Question 1 options

2. @Slf4j does what?

Question 2 options

3. What is a common mistake when implementing Logging Deep Dive?

Question 3 options

Flashcards

Question

Spring default logging?

Click to reveal answer

Answer

Logback

Question

@Slf4j?

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Answer

Lombok: creates Logger instance

Question

Logging Deep Dive best practices

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Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1. SLF4J API + Logback implementation
  • 2. @Slf4j for easy logging
  • 3. Log levels: TRACE < DEBUG < INFO < WARN < ERROR
  • 4. Always include context in log messages

Interview Tips

  • • Configure logging properly
  • • Use appropriate log levels

Cheat Sheet

Logging

  • SLF4J (API) + Logback (implementation)
  • @Slf4j: creates logger
  • Levels: TRACE < DEBUG < INFO < WARN < ERROR
  • Include context in messages