How do you expose application metrics in Spring Boot?

Table of Contents

• Introduction
• Exposing Metrics in Spring Boot with Actuator
  • 1. Adding Dependencies for Spring Boot Actuator and Micrometer
  • 2. Enabling Metrics Endpoints in application.properties
  • 3. Viewing Exposed Metrics
  • 4. Exposing Custom Metrics
  • 5. Monitoring Performance with Timers and Gauges
• Practical Example: Exposing Metrics in a Spring Boot Application
• Conclusion

Introduction

Monitoring the health and performance of an application is crucial for ensuring its reliability and efficiency in production environments. In Spring Boot, exposing application metrics is made easy with the use of Spring Boot Actuator and Micrometer. These tools provide a way to gather, track, and expose valuable application performance data, such as memory usage, request rates, and JVM statistics, among other things. This guide will walk you through how to expose and customize metrics in your Spring Boot application.

Exposing Metrics in Spring Boot with Actuator

1. Adding Dependencies for Spring Boot Actuator and Micrometer

The first step to exposing application metrics is to include the necessary dependencies in your Spring Boot project. Spring Boot Actuator is the core library that provides endpoints for exposing metrics, while Micrometer acts as the metrics facade that collects and exposes the data in various formats (like Prometheus, StatsD, etc.).

Add the following dependencies to your pom.xml if you’re using Maven:

For Gradle, you can add:

2. Enabling Metrics Endpoints in application.properties

Spring Boot Actuator exposes several built-in endpoints that provide insights into your application's health and metrics. By default, some of these endpoints might be disabled for security reasons. You need to configure them in the application.properties (or application.yml) file.

Add the following properties to expose the most common Actuator endpoints:

This configuration exposes the /actuator/health and /actuator/metrics endpoints, along with the /actuator/prometheus endpoint if you're using Prometheus for monitoring.

3. Viewing Exposed Metrics

Once you have set up the Actuator and Micrometer dependencies, and configured the endpoints, you can access the exposed metrics via the following URLs (assuming your application is running locally):

• Health endpoint: http://localhost:8080/actuator/health
  Displays the health status of your application (e.g., UP or DOWN).
• Metrics endpoint: http://localhost:8080/actuator/metrics
  Displays a list of all metrics collected by Micrometer.
• Prometheus endpoint (if configured): http://localhost:8080/actuator/prometheus
  Exposes metrics in a format suitable for scraping by Prometheus.

4. Exposing Custom Metrics

In addition to the default metrics provided by Spring Boot and Micrometer, you can also define and expose custom metrics for your application. This can be useful to monitor specific business or application logic.

Here’s how you can define a custom counter metric:

You can then use this incrementCustomCounter method in your application whenever you want to increment the custom metric. This counter will now appear in the /actuator/metrics endpoint.

5. Monitoring Performance with Timers and Gauges

Micrometer also allows you to create timers and gauges to measure performance-related metrics, such as method execution time and resource usage.

Timer Example (measuring execution time):

The sample_timer will now track how long the business logic takes to execute.

Gauge Example (tracking memory usage):

This gauge tracks the amount of memory used by the JVM.

Practical Example: Exposing Metrics in a Spring Boot Application

Here’s a simple example of how to set up and access metrics in a Spring Boot application.

1. Add dependencies for Spring Boot Actuator and Micrometer.
2. Configure application.properties to expose the /metrics endpoint.
3. Define custom metrics using MeterRegistry, such as counters or timers.
4. Access the metrics via http://localhost:8080/actuator/metrics.

Conclusion

Exposing application metrics in Spring Boot is made easy with Spring Boot Actuator and Micrometer. By simply adding the right dependencies and configuration, you can monitor the health and performance of your application. You can also define custom metrics to track application-specific data, such as business logic execution times or resource usage. These tools help ensure that your Spring Boot application remains performant, reliable, and easier to troubleshoot in production environments.