Expose metrics from a Spring Boot application

This guide shows you how to instrument a Spring Boot application so that its metrics are sent to KubeStack+ and visible in Grafana.

How it works

The OpenTelemetry Spring Boot starter emits JVM, web server, and database metrics as soon as it is on the classpath. You point the SDK at the in-cluster OTel collector through your values.yaml for the Stakater Application Helm Chart; the platform receives the metrics over OTLP and stores them in Mimir.

1. Add the OpenTelemetry Spring Boot starter

Add the starter to your pom.xml:

<dependency>
    <groupId>io.opentelemetry.instrumentation</groupId>
    <artifactId>opentelemetry-spring-boot-starter</artifactId>
</dependency>

JVM, web server, and database metrics are emitted automatically once the starter is on the classpath.

2. Point the SDK at the in-cluster OTel collector

Set the OTel SDK environment variables in your application's values.yaml for the Stakater Application Helm Chart:

deployment:
  env:
    - name: OTEL_SERVICE_NAME
      value: your-service-name
    - name: OTEL_EXPORTER_OTLP_ENDPOINT
      value: http://otel-collector.observability.svc.cluster.local:4317
    - name: OTEL_METRICS_EXPORTER
      value: otlp

Commit the change; ArgoCD applies it; metrics appear in Grafana within a minute.

3. Add a custom metric

The OpenTelemetry API lets you register counters, gauges, and histograms in code. The example below registers a counter that increments every time a review receives a rating of three or below:

import io.opentelemetry.api.GlobalOpenTelemetry;
import io.opentelemetry.api.metrics.LongCounter;
import io.opentelemetry.api.metrics.Meter;

private final Meter meter = GlobalOpenTelemetry.getMeter("nordmart-review");
private final LongCounter ratingCounter = meter
    .counterBuilder("nordmart.review.low_ratings")
    .setDescription("Total number of ratings below 3")
    .build();

public void recordRating(int rating) {
    if (rating <= 3) {
        ratingCounter.add(1);
    }
}

The counter appears in Grafana as nordmart_review_low_ratings_total once the first rating is recorded.

Next step

Continue to Logs to forward your application logs to the platform.