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Spring Boot Example with Camel exposing REST services using Apache CXF, collecting distributed tracing using OpenTelemetry

Introduction

This example illustrates how to use Spring Boot with Camel and Apache CXF implementing REST services using bottom-up approach.

If you are using REST services directly from Camel and you want to use OpenTelemetry please refer to the dedicated example

There are 3 services which communicate each other, starting from the random service:

  • random: the main service, exposes the entry point REST service and store the results

  • even: the service that verifies the even numbers

  • odd: the service that verifies the odd numbers

moreover there is a common module containing common classes

overview

Build

You can build this example using the following command; it will also download the OpenTelemetry agent used to instrument the applications:

$ mvn package -Potel-agent

Run

Run docker-compose to start all the needed services:

$ docker-compose -f containers/docker-compose.yml up -d

the command runs:

Run each services on separated terminals:

$ source containers/env.sh \
    && java -javaagent:target/opentelemetry-javaagent.jar \
    -Dotel.service.name=random \
    -jar rest-cxf-otel-random/target/*.jar
$ source containers/env.sh \
    && java -javaagent:target/opentelemetry-javaagent.jar \
    -Dotel.service.name=even \
    -Dserver.port=8081 \
    -jar rest-cxf-otel-even/target/*.jar
$ source containers/env.sh \
    && java -javaagent:target/opentelemetry-javaagent.jar \
    -Dotel.service.name=odd \
    -Dserver.port=8082 \
    -jar rest-cxf-otel-odd/target/*.jar

After the Spring Boot applications have been started, you can open the following URL in your web browser http://localhost:8080/services/ to access the list of services, including WADL definition

You can also access the REST endpoint from the command line:

i.e. to generate 5 random numbers run:

$ curl -X POST http://localhost:8080/services/api/play/5 -s | jq .

The command will produce an output like:

{
  "result": {
    "ODD": [
      {
        "number": 229,
        "type": "ODD"
      },
      {
        "number": 585,
        "type": "ODD"
      }
    ],
    "EVEN": [
      {
        "number": 648,
        "type": "EVEN"
      },
      {
        "number": 670,
        "type": "EVEN"
      },
      {
        "number": 846,
        "type": "EVEN"
      }
    ]
  },
  "evenCount": 3,
  "oddCount": 2
}

Now in the Jaeger UI http://localhost:16686 the traces will be available, both from Camel and from CXF instrumentation

jaeger

The services can be stopped pressing [CTRL] + [C] in the shell, and the containers can be stopped with

$ docker-compose -f containers/docker-compose.yml down

Explain the code

The dependency org.apache.cxf:cxf-integration-tracing-opentelemetry provides org.apache.cxf.tracing.opentelemetry.jaxrs.OpenTelemetryFeature that instruments the OpenTelemetry API implemented in the java agent.

The feature is injected in the Spring context

link:rest-cxf-otel-common/src/main/java/org/apache/camel/example/springboot/cxf/otel/CxfConfig.java[role=include]

and then it is configured in the Camel route as provider in the cxfrs endpoint

link:rest-cxf-otel-random/src/main/java/org/apache/camel/example/springboot/cxf/otel/CamelRouter.java[role=include]

When the feature is enabled it is possible to add custom tags or logs using TracerContext from CXF

link:rest-cxf-otel-random/src/main/java/org/apache/camel/example/springboot/cxf/otel/RandomService.java[role=include]
link:rest-cxf-otel-random/src/main/java/org/apache/camel/example/springboot/cxf/otel/RandomServiceImpl.java[role=include]

Help and contributions

If you hit any problem using Camel or have some feedback, then please let us know.

We also love contributors, so get involved :-)

The Camel riders!