Article 15: Logging & Monitoring in Spring Boot

1. Introduction

If something breaks in production and you can’t see what happened, you’re blind.

Logging and monitoring help you:

• Debug issues quickly
• Understand application behavior
• Monitor health and performance

Spring Boot provides excellent defaults plus powerful extensions.

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2. Logging in Spring Boot (Basics)

Spring Boot uses:

• SLF4J (logging API)
• Logback (default implementation)

You don’t need to add dependencies — logging works out of the box.

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3. Using Logger in Code

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@RestController
public class UserController {

    private static final Logger log =
            LoggerFactory.getLogger(UserController.class);

    @GetMapping("/log-test")
    public String test() {
        log.info("Info log");
        log.warn("Warning log");
        log.error("Error log");
        return "Check logs";
    }
}

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4. Log Levels Explained

Level	Usage
TRACE	Very detailed
DEBUG	Debugging
INFO	Normal flow
WARN	Potential issues
ERROR	Failures

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5. Configuring Log Levels

In application.properties:

logging.level.root=INFO
logging.level.com.example.demo=DEBUG

This allows:

• Less noise globally
• More detail for your code

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6. Log Format Customization

logging.pattern.console=%d{yyyy-MM-dd HH:mm:ss} %-5level %logger - %msg%n

Readable logs = faster debugging.

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7. Why Monitoring Is Important

Monitoring tells you:

• Is the app running?
• Is it healthy?
• How many requests?
• Memory usage?

This is critical in production.

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8. Spring Boot Actuator

Spring Boot Actuator provides:

• Health checks
• Metrics
• Application info

Add dependency:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

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9. Important Actuator Endpoints

Endpoint	Purpose
/actuator/health	App health
/actuator/info	App info
/actuator/metrics	Metrics
/actuator/env	Environment

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10. Exposing Actuator Endpoints

management.endpoints.web.exposure.include=health,info,metrics

Access:

http://localhost:8080/actuator/health

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11. Custom Health Indicator

@Component
public class CustomHealthIndicator implements HealthIndicator {

    @Override
    public Health health() {
        boolean healthy = true;

        if (healthy) {
            return Health.up().build();
        }
        return Health.down().withDetail("Error", "Something failed").build();
    }
}

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12. Securing Actuator Endpoints

Never expose all actuator endpoints publicly.

management.endpoints.web.exposure.include=health

Secure others via Spring Security.

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13. Common Logging & Monitoring Mistakes

❌ Logging sensitive data
❌ Too much DEBUG in production
❌ No health checks
❌ Ignoring logs until failure

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14. Best Practices

✔ Log meaningful events
✔ Use proper log levels
✔ Monitor health endpoints
✔ Combine logs + metrics

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15. What You Should Understand Before Moving On

You should now know:

• How logging works in Spring Boot
• How to configure log levels
• What Actuator provides
• How to monitor application health

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16. What’s Next?

➡ Article 16: Performance & Caching

• Why caching matters
• @Cacheable
• Improving response time

Type Next when you’re ready.