Java / Maven

Use OpenTelemetry with Zipkin and the Micronaut Framework for Microservice Distributed Tracing

Use Zipkin distributed tracing to investigate the behavior of your Micronaut applications.

Sergio del Amo

On this guide

In this section

Getting Started

In this guide, we will integrate Zipkin with a Micronaut application composed of three microservices.

Zipkin is a distributed tracing system. It helps gather timing data needed to troubleshoot latency problems in microservice architectures. It manages both the collection and lookup of this data.

You will discover how the Micronaut framework eases Zipkin integration.

What you will need

To complete this guide, you will need the following:

Some time on your hands
A decent text editor or IDE (e.g. IntelliJ IDEA)
JDK 21 or greater installed with JAVA_HOME configured appropriately

Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can go right to the completed example.

Download and unzip the source

Writing the Application

To learn more about this sample application, read the guide. The application contains three microservices.

bookcatalogue - This returns a list of books. It uses a domain consisting of a book name and an ISBN.
bookinventory - This exposes an endpoint to check whether a book has sufficient stock to fulfill an order. It uses a domain consisting of a stock level and an ISBN.
bookrecommendation - This consumes previous services and exposes an endpoint that recommends book names that are in stock.

The bookrecommendation service consumes endpoints exposed by the other services. The following image illustrates the application flow:

A request to bookrecommendation (http://localhost:8080/books) triggers several requests through our microservices mesh.

Setup IntelliJ IDEA to develop Micronaut Applications.

Zipkin and the Micronaut Framework

Install Zipkin via Docker

The quickest way to start Zipkin is via Docker:

docker run -d -p 9411:9411 openzipkin/zipkin

OpenTelemetry dependencies

OpenTelemetry annotations

To enable OpenTelemetry annotations, every service includes the following annotation processor:

pom.xml

<!-- Add the following to your annotationProcessorPaths element -->
<path>
    <groupId>io.micronaut.tracing</groupId>
    <artifactId>micronaut-tracing-opentelemetry-annotation</artifactId>
</path>

Micronaut OpenTelemetry HTTP

To enable creation of span objects on every HTTP server request, client request, server response, and client response, each service includes the following dependency:

pom.xml

<dependency>
    <groupId>io.micronaut.tracing</groupId>
    <artifactId>micronaut-tracing-opentelemetry-http</artifactId>
    <scope>compile</scope>
</dependency>

OpenTelemetry Protocol Exporter

An exporter is a component in the OpenTelemetry Collector configured to send data to different systems/back-ends.

Each service adds the OpenTelemetry Zipkin exporter dependency.

pom.xml

<dependency>
    <groupId>io.opentelemetry</groupId>
    <artifactId>opentelemetry-exporter-zipkin</artifactId>
    <scope>compile</scope>
</dependency>

Each service sets zipkin as the exporter in configuration:

bookcatalogue/java/src/main/resources/application.properties

otel.traces.exporter=zipkin

Disable OpenTelemetry in Tests

Disable Micronaut Open Telemetry integration in tests:

bookcatalogue/java/src/test/resources/application-test.properties

micronaut.otel.enabled=false

Changes to Book inventory

Annotate the BookController method with @ContinueSpan and the method parameter with @SpanTag:

bookinventory/java/src/main/java/example/micronaut/BooksController.java

package example.micronaut;

import io.micronaut.http.MediaType;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Produces;
import io.micronaut.tracing.annotation.ContinueSpan;
import io.micronaut.tracing.annotation.SpanTag;

import jakarta.validation.constraints.NotBlank;
import java.util.Optional;

@Controller("/books")
public class BooksController {

    @Produces(MediaType.TEXT_PLAIN)
    @Get("/stock/{isbn}")
    @ContinueSpan // 
    public Boolean stock(@SpanTag("stock.isbn") @NotBlank String isbn) { // 
        return bookInventoryByIsbn(isbn).map(bi -> bi.getStock() > 0).orElse(null);
    }

    private Optional<BookInventory> bookInventoryByIsbn(String isbn) {
        if (isbn.equals("1491950358")) {
            return Optional.of(new BookInventory(isbn, 4));

        } else if (isbn.equals("1680502395")) {
            return Optional.of(new BookInventory(isbn, 0));
        }
        return Optional.empty();
    }
}

1	The `@ContinueSpan` annotation will continue an existing span, wrapping the method call or reactive type.
2	The `@SpanTag` annotation can be used on method arguments to include the value of each argument within a Span’s tags. When you use `@SpanTag` you need either to annotate the method with `@NewSpan` or `@ContinueSpan`.

Running the Application

Run bookcatalogue microservice:

To run the application, execute ./mvnw mn:run.

...
14:28:34.034 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 499ms. Server Running: http://localhost:8081

Run bookinventory microservice:

To run the application, execute ./mvnw mn:run.

...
14:31:13.104 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 506ms. Server Running: http://localhost:8082

Run bookrecommendation microservice:

To run the application, execute ./mvnw mn:run.

...
14:31:57.389 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 523ms. Server Running: http://localhost:8080

You can run a cURL command to test the whole application:

curl http://localhost:8080/books

[{"name":"Building Microservices"}]

You can then navigate to http://localhost:9411 to access the Zipkin UI.

The previous request generates a trace composed of 5 spans.

In the previous image, you can see the requests to bookinventory are made in parallel.

In the previous image, you can see that:

Whenever a Micronaut HTTP client executes a new network request, a span is involved.
Whenever a Micronaut server receives a request, a span is involved.

The stock.isbn tags that we configured with @SpanTag are present, as shown in the next image:

Generate a Micronaut Application Native Executable with GraalVM

We will use GraalVM, an advanced JDK with ahead-of-time Native Image compilation, to generate a native executable of this Micronaut application.

Compiling Micronaut applications ahead of time with GraalVM significantly improves startup time and reduces the memory footprint of JVM-based applications.

Note	Only Java and Kotlin projects support using GraalVM’s `native-image` tool. Groovy relies heavily on reflection, which is only partially supported by GraalVM.

GraalVM Installation

The easiest way to install GraalVM on Linux or Mac is to use SDKMan.io.

Java 25

sdk install java 25.0.2-graal

For installation on Windows, or for a manual installation on Linux or Mac, see the GraalVM Getting Started documentation.

The previous command installs Oracle GraalVM, which is free to use in production and free to redistribute, at no cost, under the GraalVM Free Terms and Conditions.

Alternatively, you can use the GraalVM Community Edition:

Java 25

sdk install java 25.0.2-graalce

Native Executable Generation

To generate a native executable using Maven, run:

./mvnw package -Dpackaging=native-image

The native executable is created in the target directory and can be run with target/micronautguide.

It is possible to customize the name of the native executable or pass additional build arguments using the Maven plugin for GraalVM Native Image building. Declare the plugin as follows:

pom.xml

<plugin>
    <groupId>org.graalvm.buildtools</groupId>
    <artifactId>native-maven-plugin</artifactId>
    <version>0.11.5</version>
    <configuration>
         
         <imageName>mn-graalvm-application</imageName>
        <buildArgs>
          
          <buildArg>-Ob</buildArg>
        </buildArgs>
    </configuration>
</plugin>

1	The native executable name will now be `mn-graalvm-application`.
2	It is possible to pass extra build arguments to `native-image`. For example, `-Ob` enables the quick build mode.

Start the native images for the three microservices and run the same curl request as before to check that everything works with GraalVM.

Next Steps

As you have seen in this guide, without any annotations, you can get distributed tracing up and running quickly with the Micronaut framework.

The Micronaut framework includes several annotations to give you more flexibility. We introduced the @ContinueSpan and @SpanTag annotations. Also, you have at your disposal the @NewSpan annotation, which will create a new span, wrapping the method call or reactive type.

Make sure to read more about Tracing with Zipkin in the Micronaut framework.

Help with the Micronaut Framework

The Micronaut Foundation sponsored the creation of this Guide. A variety of consulting and support services are available.

License

Note	All guides are released with an Apache License 2.0 for the code and a Creative Commons Attribution 4.0 license for the writing and media (images).