@F_SO_K response was for http.server.requests, here adjusted for the actual question of http.client.requests

@Component
public class ExtendedHttpClientMetrics extends DefaultClientRequestObservationConvention {

    private static final Logger log = LoggerFactory.getLogger(ExtendedHttpClientMetrics.class);
    
    @Override
    public KeyValues getLowCardinalityKeyValues(final ClientRequestObservationContext context) {
        var before = super.getLowCardinalityKeyValues(context);
        log.trace("Before {}", before);
        return before.and(custom(context));
    }

    protected KeyValues custom(final ClientRequestObservationContext context) {
        var uri = context.getCarrier().getURI();
        log.trace("Custom client request observation context: uri {}", uri);
        return KeyValues.of("uri", uri.getPath());
    }

}