Red Hat

Eclipse MicroProfile OpenTracing comes to WildFly

Until WildFly 19 you could use Eclipse MicroProfile OpenTracing (MPOT) to trace your application using environment variables relying on the SmallRye OpenTracing implementation. With WildFly 19 you can now configure several Jaeger Tracers to be used in your applications.

Installing Jaeger

Let’s start a jaeger instance using docker :

docker run -d --name jaeger \
  -p 6831:6831/udp \
  -p 5778:5778 \
  -p 14268:14268 \
  -p 16686:16686 \

Now, you can navigate to http://localhost:16686 to access the Jaeger UI.

Configuring the OpenTracing subsystem

You can use either UDP or TCP to send your log spans to Jaeger. Note that those configurations are exclusive, so if you configure a TCP endpoint then Jaeger won’t use the UDP configuration.

Using UDP

First we use the WildFly CLI tool to define an outbound socket binding towards the Jaeger tracer.

[standalone@localhost:9990 /] /socket-binding-group=standard-sockets/remote-destination-outbound-socket-binding=jaeger:add(host=localhost, port=6831)
{"outcome" => "success"}

Now we can define our MPOT tracer configuration:

[standalone@localhost:9990 /] /subsystem=microprofile-opentracing-smallrye/jaeger-tracer=jaeger-demo:add(sampler-type=const, sampler-param=1, reporter-log-spans=true, sender-binding=jaeger)
{"outcome" => "success"}

Using TCP

If you want to use TCP instead of UDP you need to configure the sender-endpoint and set its value to http://localhost:14268/api/traces.

[standalone@localhost:9990 /] /subsystem=microprofile-opentracing-smallrye/jaeger-tracer=jaeger-demo:write-attribute(name="sender-endpoint", value="http://localhost:14268/api/traces")
    "outcome" => "success",
    "response-headers" => {
        "operation-requires-reload" => true,
        "process-state" => "reload-required"
[standalone@localhost:9990 /] reload

Setting the default tracer

Let’s define this new tracer as the default tracer to be used by WildFly:

[standalone@localhost:9990 /] /subsystem=microprofile-opentracing-smallrye:write-attribute(name=default-tracer, value=jaeger-demo)
    "outcome" => "success",
    "response-headers" => {
        "operation-requires-reload" => true,
        "process-state" => "reload-required"
[standalone@localhost:9990 /] reload

Instead of relying on the default tracer attribute, you can use the web.xml deployment descriptor and set the init-parameter smallrye.opentracing.tracer.configuration to the name of the tracer to use.

Deploying a demo application

We provide a sample application at This application is a simple JAXRS endpoint producing XML or JSON and failing randomly.

git clone
cd opentracing-demo
mvn clean install
cp target/opentracing-demo.war $WILDFLY_HOME/standalone/deployments

Now, you can navigate to http://localhost:8080/opentracing-demo to access the deployed application. Generate a few traces by clicking on the links several times. Note that in order to demonstrate error traces the application deliberately throws exceptions randomly, so don’t be surprised if some requests fail.

Now open the Jaeger UI and search for traces related to the service opentracing-demo.war, you should see the result of your previous actions.


Emmanuel Hugonnet

Emmanuel works at Red Hat on WildFly Core. He currently works on domain management and also maintains the NetBeans WildFly plugin.

Location:  France

Occupation:  Software Engineer

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