Metrics with Micrometer in Spring Boot

Introduction

Micrometer helps you measure how your Spring Boot app is doing. It tracks things like how fast requests are or how many errors happen.

You want to see how many users visit your website each minute.

You need to check if your app is slow or fast during certain times.

You want to count how many times a feature is used.

You want to watch for errors or failures in your app.

You want to send app performance data to monitoring tools like Prometheus.

Syntax

Spring Boot

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

@Component
public class MyMetrics {
    private final MeterRegistry meterRegistry;

    public MyMetrics(MeterRegistry meterRegistry) {
        this.meterRegistry = meterRegistry;
    }

    public void recordEvent() {
        meterRegistry.counter("myapp.events.count").increment();
    }
}

MeterRegistry is the main object to create and update metrics.

Use counters to count events, timers to measure durations, and gauges for current values.

Examples

This counts how many requests happened.

Spring Boot

meterRegistry.counter("requests.total").increment();

This measures how long a block of code takes.

Spring Boot

import io.micrometer.core.instrument.Timer;

Timer.Sample sample = Timer.start(meterRegistry);
// code to time
sample.stop(meterRegistry.timer("requests.latency"));

This tracks the current size of a queue.

Spring Boot

meterRegistry.gauge("queue.size", queue, Queue::size);

Sample Program

This Spring Boot app has one endpoint /hello. Each time you visit it, Micrometer counts the request.

Spring Boot

package com.example.metricsdemo;

import io.micrometer.core.instrument.MeterRegistry;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
public class MetricsDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(MetricsDemoApplication.class, args);
    }
}

@RestController
class DemoController {
    private final MeterRegistry meterRegistry;

    public DemoController(MeterRegistry meterRegistry) {
        this.meterRegistry = meterRegistry;
    }

    @GetMapping("/hello")
    public String hello() {
        meterRegistry.counter("hello.requests.count").increment();
        return "Hello, Micrometer!";
    }
}

Important Notes

Micrometer works with many monitoring systems like Prometheus, Datadog, and others.

Spring Boot auto-configures Micrometer if you add the right starter dependency.

Remember to name your metrics clearly so they are easy to understand later.

Summary

Micrometer helps track app performance and events easily.

Use counters, timers, and gauges for different types of metrics.

Spring Boot makes it simple to add Micrometer and start measuring.