By default, OpenTracingClientProvider will try to pass the currently active span through HTTP headers on each service invocation. If there is no active spans, the new span will be created and passed through HTTP headers on per-invocation basis. Essentially, for JAX-RS applications just registering OpenTracingClientProvider on the client and OpenTracingProvider on the server is enough to have tracing context to be properly passed everywhere. The only configuration part which is necessary are span reportsreporters(s) and sampler(s) which are, not surprisingly, specific to distributing tracing framework you have chosen.

It is also worth to mention the way Apache CXF attaches the description to spans. With regards to the client integration, the description becomes a full URL being invoked prefixed by HTTP method, for example: GET http://localhost:8282/books. On the server side integration, the description becomes a relative JAX-RS resource path prefixed by HTTP method, f.e.: GET books, POST book/123. On the server side integration, the description becomes a relative JAX-RS resource path prefixed by HTTP method, f.e.: GET books, POST book/123

OpenTracing APIs

OpenTracing Java API is evolving very fast and, sadly but not surprisingly, often the changes being made are not backward compatible. The Apache CXF 3.2.x release branch stays on OpenTracing Java API 0.30.0 as of now, while the Apache CXF 3.3.x is using OpenTracing Java API 0.31.0. There arequite many major differences between both APIs but Apache CXF is trying hard to smooth it over. It is worth to mention that OpenTracing-compatible clients and servers may not depend on the same APIs version, the only issue you will run into is related to compatibility of the provided Java clients for the tracer of your choice.

OpenTracing API v0.30.0 and Apache CXF 3.2.x

Configuring Client

In this section and below, all the code snippets are going to be based on Jaeger distributed tracing framework (release 0.20.6+), although everything we are going to discuss is equally applicable to any other existing alternatives. Essentially, the only dependency Apache CXF integration relies on is the Tracer instance.

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Code Block

	java
	java

final Tracer tracer = new Configuration("jaxrs-client", 
        new Configuration.SamplerConfiguration(ConstSampler.TYPE, 1), /* or any other Sampler */
        new Configuration.ReporterConfiguration(new HttpSender("http://localhost:14268/api/traces")) /* or any other Sender */
    ).getTracer();

// This method should only be called once during the application initialization phase.
GlobalTracer.register(tracer);

// No explicit Tracer instance is required, it will be picked off the GlobalTracer using get() method
final OpenTracingClientProvider provider = new OpenTracingClientProvider();

Configuring Server

Server configuration is a bit simpler than the client one thanks to the feature class available, OpenTracingFeature. Depending on the way the Apache CXF is used to configure JAX-RS services, it could be part of JAX-RS application configuration, for example:

...

Once the span reporter and sampler are properly configured, all generated spans are going to be collected and available for analysis and/or visualization.

Distributed Tracing In Action: Usage Scenarios

In the following subsections we are going to walk through many different scenarios to illustrate the distributed tracing in action, starting from the simplest ones and finishing with asynchronous JAX-RS services. All examples assume that configuration has been done (see please Configuring Client and Configuring Server sections above).

Example #1: Client and Server with default distributed tracing configured

In the first example we are going to see the effect of using default configuration on the client and on the server, with only OpenTracingClientProvider and OpenTracingProvider registered. The JAX-RS resource endpoint is pretty basic stubbed method:

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