Spring Boot Monitoring with Micrometer

What You’ll Learn 📚

• Core concepts of application monitoring
• Key terminology related to Micrometer and Spring Boot
• Step-by-step examples from basic to advanced
• Common questions and troubleshooting tips

Introduction to Application Monitoring

Application monitoring is like having a health check-up for your software. It helps you understand how your application is performing and identify any issues before they become big problems. With monitoring, you can track metrics such as response times, error rates, and system resource usage.

Why Use Micrometer?

Micrometer is a powerful library that provides a simple facade over the instrumentation clients for different monitoring systems. It integrates seamlessly with Spring Boot, making it a popular choice for developers.

Think of Micrometer as a universal adapter for monitoring tools. It allows you to plug in different monitoring systems without changing your code!

Key Terminology

• Metrics: Quantitative measures of your application’s performance, such as response time or CPU usage.
• Instrumentation: The process of adding monitoring capabilities to your application.
• Facade: A design pattern that provides a simplified interface to a complex system.

Getting Started: The Simplest Example

Let’s start with a basic example to get Micrometer up and running in a Spring Boot application.

curl https://start.spring.io/starter.zip -d dependencies=web,actuator,micrometer -o demo.zip

<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-core</artifactId>
</dependency>

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

Progressively Complex Examples

Example 1: Custom Metrics

Let’s create a custom metric to track the number of times a specific endpoint is accessed.

import io.micrometer.core.instrument.Counter;
import io.micrometer.core.instrument.MeterRegistry;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

    private final Counter counter;

    public MyController(MeterRegistry registry) {
        this.counter = Counter.builder("my.custom.counter")
                .description("A custom counter for tracking endpoint calls")
                .register(registry);
    }

    @GetMapping("/custom")
    public String customEndpoint() {
        counter.increment();
        return "Custom endpoint accessed!";
    }
}

Example 2: Timer Metrics

Timers are useful for measuring the duration of tasks. Let’s add a timer to measure how long it takes to process a request.

import io.micrometer.core.instrument.Timer;
import io.micrometer.core.instrument.MeterRegistry;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.TimeUnit;

@RestController
public class TimerController {

    private final Timer timer;

    public TimerController(MeterRegistry registry) {
        this.timer = Timer.builder("my.timer")
                .description("A timer for request processing")
                .register(registry);
    }

    @GetMapping("/time")
    public String timeEndpoint() {
        return timer.record(() -> {
            try {
                // Simulate a task taking time
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
            return "Task completed!";
        });
    }
}

Example 3: Gauge Metrics

Gauges are used to measure values that can go up and down, like memory usage. Let’s create a gauge to monitor a random value.

import io.micrometer.core.instrument.Gauge;
import io.micrometer.core.instrument.MeterRegistry;
import org.springframework.stereotype.Component;

import java.util.concurrent.atomic.AtomicInteger;

@Component
public class GaugeExample {

    private final AtomicInteger randomValue = new AtomicInteger(0);

    public GaugeExample(MeterRegistry registry) {
        Gauge.builder("my.gauge", randomValue, AtomicInteger::get)
                .description("A gauge for random values")
                .register(registry);
    }

    public void updateValue(int newValue) {
        randomValue.set(newValue);
    }
}

Common Questions and Answers

1. What is Micrometer?

   Micrometer is a metrics instrumentation library for Java applications, providing a simple facade over different monitoring systems.

2. Why should I use Micrometer with Spring Boot?

   Micrometer integrates seamlessly with Spring Boot, allowing you to easily add monitoring capabilities to your application.

3. How do I access the metrics in my Spring Boot application?

   Metrics are available at the /actuator/metrics endpoint. You can customize which metrics are exposed through your configuration.

4. Can I create custom metrics?

   Yes! You can create custom counters, timers, and gauges to monitor specific aspects of your application.

5. What monitoring systems can I use with Micrometer?

   Micrometer supports many systems, including Prometheus, Graphite, and New Relic, among others.

6. How do I troubleshoot missing metrics?

   Ensure that the necessary actuator endpoints are enabled and that your application has the correct dependencies. Check the logs for any errors related to Micrometer.

Troubleshooting Common Issues

If you don’t see any metrics, double-check that the actuator endpoints are enabled in your application.properties or application.yml.

Here are some common issues and how to resolve them:

• Missing Metrics: Ensure your dependencies are correctly set up and that the actuator endpoints are exposed.
• Errors in Logs: Check for any exceptions related to Micrometer or your monitoring system.
• Incorrect Metric Values: Verify that your custom metrics are being updated correctly in your code.

Practice Exercises

Try implementing the following exercises to reinforce your learning:

1. Create a custom counter metric to track the number of failed login attempts in your application.
2. Add a timer to measure the duration of a database query.
3. Implement a gauge to monitor the number of active user sessions.

Remember, practice makes perfect! 💪

Additional Resources

• Micrometer Documentation
• Spring Boot Documentation
• Spring Boot Actuator Guide