I was trying out Spring Boot 3.2.0-RC2 and was quite surprised that a RestClient created via RestClient.builder().build() is not auto-instrumented like RestTemplate and WebClient currently are. If I create a RestClientCustomizer in a similar fashion to RestTemplateObservationConfiguration, then observations are properly created for HTTP requests as one could expect:

    @Bean
    RestClientCustomizer observationRestClientCustomizer(
            ObservationRegistry observationRegistry,
            ObjectProvider<ClientRequestObservationConvention> customConvention,
            ObservationProperties properties) {
        String name = properties.getHttp().getClient().getRequests().getName();
        ClientRequestObservationConvention observationConvention = customConvention
            .getIfAvailable(() -> new DefaultClientRequestObservationConvention(name));
        return builder -> builder
                .observationRegistry(observationRegistry)
                .observationConvention(observationConvention);
    }

Adding this as an auto configuration would improve the out-of-the-box experience for the new RestClient.