Spring RestClient.Builder not instrumented

[Munken]

Describe the bug

RestClient is currently instrumented using a BeanPostProcessor.

However, it is typical to use the RestClient using the RestClient.Builder e.g.

        RestClient.builder()
                .baseUrl("http://localhost:8080")
                .requestInterceptors(System.out::println)
                .build()
                .get()
                .retrieve()
                .body(String.class);

In this case no instrumentation is present.

Steps to reproduce

Create a RestClient using the Builder. Have it print its interceptors.
Observe that the list is empty.

        RestClient.builder()
                .baseUrl("http://localhost:8080")
                .requestInterceptors(System.out::println)
                .build()
                .get()
                .retrieve()
                .body(String.class);

Expected behavior

A interceptor is added to the RestClient.

Actual behavior

No interceptor is added.

Javaagent or library instrumentation version

2.17

Environment

JDK:
OpenJDK
OS:
Windows/Linux

Additional context

Solution
The RestClient should be instrumented in a similar fashion to the WebClient

Tip

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[laurit]

RestClient is currently instrumented using a BeanPostProcessor.

This instrumentation is only used with the spring boot starter. Currently agent does not directly instrument the rest client but relies on the whatever the rest client uses to make the actual http calls to be instrumented.

The RestClient should be instrumented in a similar fashion to the WebClient

Here you are linking to an instrumentation that is only used with the java agent.
It is not clear what your ask is, please clarify. I can only guess that you are looking for agent instrumentation for the rest client to add the url.template support.

[Munken]

Here you are linking to an instrumentation that is only used with the java agent. It is not clear what your ask is, please clarify. I can only guess that you are looking for agent instrumentation for the rest client to add the url.template support.

Correctt.
It was my impression that the BeanPostProcessor was also used by the java agent. Seems I was wrong.

So for the RestClient url.template to work reliably, one would need to create an instrumentation in a similar fashion to the WebFlux instrumentation.