Enabling distributed tracing in microservices

20 minutes

Git clone to get going right away:

git clone https://github.com/OpenLiberty/guide-microprofile-opentracing.git

Table of contents

Explore how to enable and customize tracing of JAX-RS and non-JAX-RS methods by using MicroProfile OpenTracing.

What you’ll learn

You will learn how to enable automatic tracing for JAX-RS methods as well as create custom tracers for non-JAX-RS methods by using MicroProfile OpenTracing.

OpenTracing is a standard API for instrumenting microservices for distributed tracing. Distributed tracing helps troubleshoot microservices by examining and logging requests as they propagate through a distributed system, allowing developers to tackle the otherwise difficult task of debugging these requests. Without a distributed tracing system in place, analyzing the workflows of operations becomes difficult, particularly in regard to pinpointing when and by whom a request is received, as well as when a response is sent back.

MicroProfile OpenTracing enables distributed tracing in microservices without adding any explicit distributed tracing code to the application. Note that the MicroProfile OpenTracing specification does not address the problem of defining, implementing, or configuring the underlying distributed tracing system. Rather, the specification makes it easy to instrument services with distributed tracing given an existing distributed tracing system.

You will configure the provided inventory and system services to use distributed tracing with MicroProfile OpenTracing. You will run these services in two separate JVMs made of two server instances to demonstrate tracing in a distributed environment. If all the components were to run on a single server, then any logging software would do the trick.

Getting started

The fastest way to work through this guide is to clone the Git repository and use the projects that are provided inside:

git clone https://github.com/openliberty/guide-microprofile-opentracing.git
cd guide-microprofile-opentracing

The start directory contains the starting project that you will build upon.

The finish directory contains the finished project that you will build.

For this guide, use Zipkin as your distributed tracing system. You can find the installation instructions for Zipkin at the Zipkin quickstart page. You are not required to use Zipkin, but keep in mind that you might need more instructions that are not listed here if you choose to use another tracing system.

Before you proceed, make sure that your Zipkin server is up and running. By default, Zipkin can be found at the http://localhost:9411 URL.

Try what you’ll build

The finish directory in the root directory of this guide contains two services that are configured to use MicroProfile OpenTracing. Feel free to give them a try before you proceed.

To try out the services, navigate to the finish directory and run the Maven install phase to build the services

mvn install

then, run the Maven liberty:start-server goal to start them in two Open Liberty servers:

mvn liberty:start-server

Make sure that your Zipkin server is running and point your browser to the http://localhost:9081/inventory/systems/localhost URL. When you visit this endpoint, you make two GET HTTP requests, one to the system service and one to the inventory service. Both of these requests are configured to be traced, so a new trace will be recorded in Zipkin. Visit the http://localhost:9411 URL or another location where you configured Zipkin to run and sort the traces by newest first. Verify that this new trace contains three spans with the following names:

get:io.openliberty.guides.inventory.inventoryresource.getpropertiesforhost
get:io.openliberty.guides.system.systemresource.getproperties
add() span

You can inspect each span by clicking it to reveal more detailed information, such as the time at which the request was received and the time at which a response was sent back.

If you examine the other traces, you might notice a red trace entry, which happens when an error is caught by the span. In this case, since one of the tests accesses the /inventory/systems/badhostname endpoint, which is invalid, an error is thrown. This behavior is expected.

When you are done checking out the services, stop both Open Liberty servers using the Maven liberty:stop-server goal:

mvn liberty:stop-server

Running the services

You’ll need to start the services to see basic traces appear in Zipkin. So, before you proceed, build and start the provided system and inventory services in the starting project. Navigate to the start directory and run the Maven install goal

mvn install

then, run the liberty:start-server goal:

mvn liberty:start-server

When the servers start, you can find the system and inventory services at the following URLs:

Existing Tracer implementation

To collect traces across your systems, you need to implement the OpenTracing Tracer interface. For this guide, you can access a bare-bones Tracer implementation for the Zipkin server in the form of a user feature for Open Liberty.

This feature is already configured for you in your pom.xml and server.xml files. It will be downloaded and installed automatically into each service when you run a Maven build. You can find the opentracingZipkin feature enabled in your server.xml file.

The download-maven-plugin Maven plug-in in your pom.xml is responsible for downloading and installing the feature.

If you want to install this feature yourself, see Enabling distributed tracing in the IBM Knowledge Centre.

server.xml

 1<server description="Sample Liberty server">
 2
 3  <featureManager>
 4    <feature>jaxrs-2.1</feature>
 5    <feature>jsonp-1.1</feature>
 6    <feature>cdi-2.0</feature>
 7    <feature>mpOpenTracing-1.1</feature>
 8    <feature>usr:opentracingZipkin-0.31</feature>
 9  </featureManager>
10
11  <opentracingZipkin host="localhost"/>
12
13  <httpEndpoint httpPort="${default.http.port}" httpsPort="${default.https.port}"
14      id="defaultHttpEndpoint" host="*" />
15
16  <!-- <logging traceSpecification="*=info:com.ibm.ws.opentracing*=all:com.ibm.ws.microprofile.opentracing*=all"/> -->
17
18  <webApplication location="inventory-service.war" contextRoot="/">
19    <!-- enable visibility to third party apis -->
20    <classloader apiTypeVisibility="api,ibm-api,spec,stable,third-party"/>
21  </webApplication>
22
23</server>

pom.xml

  1<?xml version='1.0' encoding='utf-8'?>
  2<project xmlns="http://maven.apache.org/POM/4.0.0"
  3xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
  5http://maven.apache.org/xsd/maven-4.0.0.xsd">
  6    <modelVersion>4.0.0</modelVersion>
  7
  8    <parent>
  9        <groupId>io.openliberty.guides</groupId>
 10        <artifactId>mp-opentracing</artifactId>
 11        <version>1.0-SNAPSHOT</version>
 12    </parent>
 13
 14    <artifactId>inventory-service</artifactId>
 15    <packaging>war</packaging>
 16
 17    <properties>
 18        <!-- Plugins -->
 19        <version.exec-maven-plugin>1.6.0</version.exec-maven-plugin>
 20    </properties>
 21
 22    <dependencies>
 23        <!-- Open Liberty features -->
 24        <dependency>
 25            <groupId>io.openliberty.features</groupId>
 26            <artifactId>jaxrs-2.1</artifactId>
 27            <type>esa</type>
 28        </dependency>
 29        <dependency>
 30            <groupId>io.openliberty.features</groupId>
 31            <artifactId>jsonp-1.1</artifactId>
 32            <type>esa</type>
 33        </dependency>
 34        <dependency>
 35            <groupId>io.openliberty.features</groupId>
 36            <artifactId>cdi-2.0</artifactId>
 37            <type>esa</type>
 38        </dependency>
 39        <dependency>
 40            <groupId>io.openliberty.features</groupId>
 41            <artifactId>mpOpenTracing-1.1</artifactId>
 42            <type>esa</type>
 43        </dependency>
 44        <!-- For tests -->
 45        <dependency>
 46            <groupId>junit</groupId>
 47            <artifactId>junit</artifactId>
 48        </dependency>
 49        <dependency>
 50            <groupId>org.apache.cxf</groupId>
 51            <artifactId>cxf-rt-rs-client</artifactId>
 52        </dependency>
 53        <dependency>
 54            <groupId>org.apache.cxf</groupId>
 55            <artifactId>cxf-rt-rs-extension-providers</artifactId>
 56        </dependency>
 57        <dependency>
 58            <groupId>org.glassfish</groupId>
 59            <artifactId>javax.json</artifactId>
 60        </dependency>
 61        <dependency>
 62            <groupId>org.apache.commons</groupId>
 63            <artifactId>commons-lang3</artifactId>
 64        </dependency>
 65        <!-- Support for JDK 9 and above -->
 66        <dependency>
 67            <groupId>javax.xml.bind</groupId>
 68            <artifactId>jaxb-api</artifactId>
 69        </dependency>
 70        <dependency>
 71            <groupId>com.sun.xml.bind</groupId>
 72            <artifactId>jaxb-core</artifactId>
 73        </dependency>
 74        <dependency>
 75            <groupId>com.sun.xml.bind</groupId>
 76            <artifactId>jaxb-impl</artifactId>
 77        </dependency>
 78        <dependency>
 79            <groupId>javax.activation</groupId>
 80            <artifactId>activation</artifactId>
 81        </dependency>
 82    </dependencies>
 83
 84    <profiles>
 85        <!-- Start system service before running tests -->
 86        <profile>
 87            <id>setup-test</id>
 88            <activation>
 89                <activeByDefault>true</activeByDefault>
 90            </activation>
 91            <build>
 92                <plugins>
 93                    <plugin>
 94                        <groupId>org.codehaus.mojo</groupId>
 95                        <artifactId>exec-maven-plugin</artifactId>
 96                        <version>${version.exec-maven-plugin}</version>
 97                        <executions>
 98                            <execution>
 99                                <id>test-start-system-service</id>
100                                <goals>
101                                    <goal>exec</goal>
102                                </goals>
103                                <phase>pre-integration-test</phase>
104                                <configuration>
105                                    <workingDirectory>../system</workingDirectory>
106                                    <executable>mvn${mvn.extension}</executable>
107                                    <arguments>
108                                        <argument>liberty:start-server</argument>
109                                    </arguments>
110                                </configuration>
111                            </execution>
112                        </executions>
113                    </plugin>
114                </plugins>
115            </build>
116        </profile>
117        <!-- Stop system service after running tests -->
118        <profile>
119            <id>teardown-test</id>
120            <activation>
121                <activeByDefault>false</activeByDefault>
122            </activation>
123            <build>
124                <plugins>
125                    <plugin>
126                        <groupId>org.codehaus.mojo</groupId>
127                        <artifactId>exec-maven-plugin</artifactId>
128                        <version>${version.exec-maven-plugin}</version>
129                        <executions>
130                            <execution>
131                                <id>test-stop-system-service</id>
132                                <goals>
133                                    <goal>exec</goal>
134                                </goals>
135                                <phase>post-integration-test</phase>
136                                <configuration>
137                                    <workingDirectory>../system</workingDirectory>
138                                    <executable>mvn${mvn.extension}</executable>
139                                    <arguments>
140                                        <argument>liberty:stop-server</argument>
141                                    </arguments>
142                                </configuration>
143                            </execution>
144                        </executions>
145                    </plugin>
146                </plugins>
147            </build>
148        </profile>
149    </profiles>
150
151    <build>
152        <plugins>
153            <plugin>
154                <groupId>org.apache.maven.plugins</groupId>
155                <artifactId>maven-war-plugin</artifactId>
156            </plugin>
157
158            <!-- Liberty plugin -->
159            <plugin>
160                <groupId>net.wasdev.wlp.maven.plugins</groupId>
161                <artifactId>liberty-maven-plugin</artifactId>
162                <configuration>
163                    <configFile>src/main/liberty/config/server.xml</configFile>
164                    <include>usr</include>
165                    <bootstrapProperties>
166                        <default.http.port>${inv.service.http.port}</default.http.port>
167                        <default.https.port>${inv.service.https.port}</default.https.port>
168                        <system.http.port>${sys.service.http.port}</system.http.port>
169                    </bootstrapProperties>
170                </configuration>
171                <executions>
172                    <execution>
173                        <id>install-apps</id>
174                        <configuration>
175                            <appsDirectory>apps</appsDirectory>
176                            <stripVersion>true</stripVersion>
177                            <installAppPackages>project</installAppPackages>
178                            <looseApplication>true</looseApplication>
179                        </configuration>
180                    </execution>
181                    <execution>
182                        <id>install-feature</id>
183                        <configuration>
184                            <skip>true</skip>
185                        </configuration>
186                    </execution>
187                </executions>
188            </plugin>
189
190            <!-- For downloading files -->
191            <plugin>
192                <groupId>com.googlecode.maven-download-plugin</groupId>
193                <artifactId>download-maven-plugin</artifactId>
194                <version>${version.download-maven-plugin}</version>
195                <executions>
196                    <execution>
197                        <id>install-tracer</id>
198                        <phase>prepare-package</phase>
199                        <goals>
200                            <goal>wget</goal>
201                        </goals>
202                        <configuration>
203                            <url>${zipkin.usr.feature}</url>
204                            <unpack>true</unpack>
205                            <outputDirectory>
206                                ${project.build.directory}/liberty/wlp/usr
207                            </outputDirectory>
208                        </configuration>
209                    </execution>
210                </executions>
211            </plugin>
212
213            <!-- Plugin to run unit tests -->
214            <plugin>
215                <groupId>org.apache.maven.plugins</groupId>
216                <artifactId>maven-surefire-plugin</artifactId>
217            </plugin>
218
219            <!-- Plugin to run functional tests -->
220            <plugin>
221                <groupId>org.apache.maven.plugins</groupId>
222                <artifactId>maven-failsafe-plugin</artifactId>
223            </plugin>
224        </plugins>
225    </build>
226</project>

Enabling distributed tracing

The MicroProfile OpenTracing feature enables tracing of all JAX-RS methods by default. To further control and customize these traces, use the @Traced annotation to enable and disable tracing of particular methods. You can also inject a custom Tracer object to create and customize spans.

Enabling distributed tracing without code instrumentation

Because tracing of all JAX-RS methods is enabled by default, you need only to enable MicroProfile OpenTracing and the Zipkin user feature in the server.xml file to see some basic traces in Zipkin.

Both of these features are already enabled in the inventory and system configuration files.

server.xml

 1<server description="Sample Liberty server">
 2
 3  <featureManager>
 4    <feature>jaxrs-2.1</feature>
 5    <feature>jsonp-1.1</feature>
 6    <feature>cdi-2.0</feature>
 7    <feature>mpOpenTracing-1.1</feature>
 8    <feature>usr:opentracingZipkin-0.31</feature>
 9  </featureManager>
10
11  <opentracingZipkin host="localhost"/>
12
13  <httpEndpoint httpPort="${default.http.port}" httpsPort="${default.https.port}"
14      id="defaultHttpEndpoint" host="*" />
15
16  <!-- <logging traceSpecification="*=info:com.ibm.ws.opentracing*=all:com.ibm.ws.microprofile.opentracing*=all"/> -->
17
18  <webApplication location="inventory-service.war" contextRoot="/">
19    <!-- enable visibility to third party apis -->
20    <classloader apiTypeVisibility="api,ibm-api,spec,stable,third-party"/>
21  </webApplication>
22
23</server>

Make sure that your services are running. Then, simply point your browser to any of their endpoints and check your Zipkin server for traces.

Enabling explicit distributed tracing

Use the @Traced annotation to define explicit span creation for specific classes and methods. If you place the annotation on a class, then it’s automatically applied to all methods within that class. If you place the annotation on a method, then it overrides the class annotation if one exists.

The @Traced annotation can be configured with the following two parameters:

The value=[true|false] parameter indicates whether or not a particular class or method is traced. For example, while all JAX-RS methods are traced by default, you can disable their tracing by using the @Traced(false) annotation. This parameter is set to true by default.
The operationName=<Span name> parameter indicates the name of the span that is assigned to the particular method that is traced. If you omit this parameter, the span will be named with the following form: <package name>.<class name>.<method name>. If you use this parameter at a class level, then all methods within that class will have the same span name unless they are explicitly overridden by another @Traced annotation.

Update the InventoryManager class.
inventory/src/main/java/io/openliberty/guides/inventory/InventoryManager.java

Enable tracing of the list() non-JAX-RS method by updating @Traced as shown.

InventoryManager.java

 1package io.openliberty.guides.inventory;
 2
 3import java.util.ArrayList;
 4import java.util.Properties;
 5import io.openliberty.guides.inventory.client.SystemClient;
 6import io.openliberty.guides.inventory.model.InventoryList;
 7import javax.enterprise.context.ApplicationScoped;
 8import javax.inject.Inject;
 9import java.util.List;
10import java.util.Collections;
11
12import org.eclipse.microprofile.opentracing.Traced;
13
14import io.opentracing.Scope;
15import io.opentracing.Tracer;
16import io.openliberty.guides.inventory.model.*;
17
18@ApplicationScoped
19public class InventoryManager {
20
21    private List<SystemData> systems = Collections.synchronizedList(new ArrayList<>());
22    private SystemClient systemClient = new SystemClient();
23
24    public Properties get(String hostname) {
25        systemClient.init(hostname, 9080);
26        Properties properties = systemClient.getProperties();
27
28        return properties;
29    }
30
31    public void add(String hostname, Properties systemProps) {
32        Properties props = new Properties();
33        props.setProperty("os.name", systemProps.getProperty("os.name"));
34        props.setProperty("user.name", systemProps.getProperty("user.name"));
35
36        SystemData system = new SystemData(hostname, props);
37        if (!systems.contains(system)) {
38                systems.add(system);
39        }
40    }
41
42    @Traced(value = true, operationName = "InventoryManager.list")
43    public InventoryList list() {
44        return new InventoryList(systems);
45    }
46
47}

Next, run the following command from the start directory to recompile your services.

mvn compile

Point to the http://localhost:9081/inventory/systems URL, check your Zipkin server, and sort the traces by newest first. You see a new trace record that is two spans long with one span for the listContents() JAX-RS method in the InventoryResource class and another span for the list() method in the InventoryManager class. Verify that these spans have the following names:

get:io.openliberty.guides.inventory.inventoryresource.listcontents
inventorymanager.list

Update the InventoryResource class
inventory/src/main/java/io/openliberty/guides/inventory/InventoryResource.java

Disable tracing of the listContents() JAX-RS method by setting @Traced(false).

InventoryResource.java

 1package io.openliberty.guides.inventory;
 2
 3import java.util.Properties;
 4import javax.enterprise.context.RequestScoped;
 5import javax.inject.Inject;
 6import javax.ws.rs.GET;
 7import javax.ws.rs.Path;
 8import javax.ws.rs.PathParam;
 9import javax.ws.rs.Produces;
10import javax.ws.rs.core.MediaType;
11import javax.ws.rs.core.Response;
12
13import org.eclipse.microprofile.opentracing.Traced;
14
15import io.openliberty.guides.inventory.model.InventoryList;
16
17@RequestScoped
18@Path("/systems")
19public class InventoryResource {
20
21    @Inject InventoryManager manager;
22
23    @GET
24    @Path("/{hostname}")
25    @Produces(MediaType.APPLICATION_JSON)
26    public Response getPropertiesForHost(@PathParam("hostname") String hostname) {
27        Properties props = manager.get(hostname);
28        if (props == null) {
29            return Response.status(Response.Status.NOT_FOUND)
30                           .entity(new Properties())
31                           .build();
32        }
33        manager.add(hostname, props);
34        return Response.ok(props).build();
35    }
36
37    @GET
38    @Traced(false)
39    @Produces(MediaType.APPLICATION_JSON)
40    public InventoryList listContents() {
41        return manager.list();
42    }
43
44}

Again, run the mvn compile command from the start directory to recompile your services. Point to the http://localhost:9081/inventory/systems URL, check your Zipkin server, and sort the traces by newest first. You see a new trace record that is just one span long for the remaining list() method in the InventoryManager class. Verify that this span has the following name:

inventorymanager.list

Injecting a custom Tracer object

The MicroProfile OpenTracing specification also makes the underlying OpenTracing Tracer instance available for use. You can access the configured Tracer by injecting it into a bean by using the @Inject annotation from the Contexts and Dependency Injections API.

Inject the Tracer object into the inventory/src/main/java/io/openliberty/guides/inventory/InventoryManager.java file. Then, use it to define a new child scope in the add() call.

Replace the InventoryManager class.
inventory/src/main/java/io/openliberty/guides/inventory/InventoryManager.java

InventoryManager.java

 1package io.openliberty.guides.inventory;
 2
 3import java.util.ArrayList;
 4import java.util.Properties;
 5import io.openliberty.guides.inventory.client.SystemClient;
 6import io.openliberty.guides.inventory.model.InventoryList;
 7import javax.enterprise.context.ApplicationScoped;
 8import javax.inject.Inject;
 9import java.util.List;
10import java.util.Collections;
11
12import org.eclipse.microprofile.opentracing.Traced;
13
14import io.opentracing.Scope;
15import io.opentracing.Tracer;
16import io.openliberty.guides.inventory.model.*;
17
18@ApplicationScoped
19public class InventoryManager {
20
21    private List<SystemData> systems = Collections.synchronizedList(new ArrayList<>());
22    private SystemClient systemClient = new SystemClient();
23    @Inject Tracer tracer;
24
25    public Properties get(String hostname) {
26        systemClient.init(hostname, 9080);
27        Properties properties = systemClient.getProperties();
28
29        return properties;
30    }
31
32    public void add(String hostname, Properties systemProps) {
33        Properties props = new Properties();
34        props.setProperty("os.name", systemProps.getProperty("os.name"));
35        props.setProperty("user.name", systemProps.getProperty("user.name"));
36
37        SystemData system = new SystemData(hostname, props);
38        if (!systems.contains(system)) {
39            try (Scope childScope = tracer.buildSpan("add() Span")
40                                              .startActive(true)) {
41                systems.add(system);
42            }
43        }
44    }
45
46    @Traced(value = true, operationName = "InventoryManager.list")
47    public InventoryList list() {
48        return new InventoryList(systems);
49    }
50
51}

The try block that you see here is called a try-with-resources statement, meaning that the childScope object is closed at the end of the statement. It’s good practice to define custom spans inside such statements. Otherwise, any exceptions that are thrown before the span is closed will leak the active span.

Next, run the following command from the start directory to recompile your services.

mvn compile

Point to the http://localhost:9081/inventory/systems/localhost URL, check your Zipkin server, and sort the traces by newest first. You see two new trace records, one for the system service and one for the inventory service. The system trace contains one span for the getProperties() method in the SystemResource class. The inventory trace contains two spans. The first span is for the getPropertiesForHost() method in the InventoryResource class. The second span is the custom span that you created around the add() call. Verify that all of these spans have the following names:

The system trace:

get:io.openliberty.guides.system.systemresource.getproperties

The inventory trace:

get:io.openliberty.guides.inventory.inventoryresource.getpropertiesforhost
add() span

This simple example shows what you can do with the injected Tracer object. More configuration options are available to you, including setting a timestamp for when a span was created and destroyed. However, these options require an implementation of their own, which does not come as a part of the Zipkin user feature that is provided. In a real-world scenario, implement all the OpenTracing interfaces that you deem necessary, which might include the SpanBuilder interface. You can use this interface for span creation and customization, including setting timestamps.

SystemResource.java

 1package io.openliberty.guides.system;
 2
 3import java.util.Properties;
 4
 5// CDI
 6import javax.enterprise.context.RequestScoped;
 7import javax.ws.rs.GET;
 8// JAX-RS
 9import javax.ws.rs.Path;
10import javax.ws.rs.Produces;
11import javax.ws.rs.core.MediaType;
12
13@RequestScoped
14@Path("properties")
15public class SystemResource {
16
17  @GET
18  @Produces(MediaType.APPLICATION_JSON)
19  public Properties getProperties() {
20    return System.getProperties();
21  }
22}

InventoryResource.java

 1package io.openliberty.guides.inventory;
 2
 3import java.util.Properties;
 4import javax.enterprise.context.RequestScoped;
 5import javax.inject.Inject;
 6import javax.ws.rs.GET;
 7import javax.ws.rs.Path;
 8import javax.ws.rs.PathParam;
 9import javax.ws.rs.Produces;
10import javax.ws.rs.core.MediaType;
11import javax.ws.rs.core.Response;
12
13import org.eclipse.microprofile.opentracing.Traced;
14
15import io.openliberty.guides.inventory.model.InventoryList;
16
17@RequestScoped
18@Path("/systems")
19public class InventoryResource {
20
21    @Inject InventoryManager manager;
22
23    @GET
24    @Path("/{hostname}")
25    @Produces(MediaType.APPLICATION_JSON)
26    public Response getPropertiesForHost(@PathParam("hostname") String hostname) {
27        Properties props = manager.get(hostname);
28        if (props == null) {
29            return Response.status(Response.Status.NOT_FOUND)
30                           .entity(new Properties())
31                           .build();
32        }
33        manager.add(hostname, props);
34        return Response.ok(props).build();
35    }
36
37    @GET
38    @Traced(false)
39    @Produces(MediaType.APPLICATION_JSON)
40    public InventoryList listContents() {
41        return manager.list();
42    }
43
44}

Testing the services

No automated tests are provided to verify the correctness of the traces. Manually verify these traces by viewing them on the Zipkin server.

A few tests are included for you to test the basic functionality of the services. If a test failure occurs, then you might have introduced a bug into the code. These tests will run automatically as a part of the Maven build process when you run the mvn install command. You can also run these tests separately from the build by using the mvn verify command, but first make sure that the servers are stopped.

Great work! You’re done!

You have just used MicroProfile OpenTracing in Open Liberty to customize how and which traces are delivered to Zipkin.

Feel free to try one of the related MicroProfile guides. They demonstrate additional technologies that you can learn to expand on top of what you built here.