Spring webflux request callback not working

I am using spring-webflux 5.1.7-RELEASE. I want to trigger the callback for webclient just before the request is sent. The code for this is:

ExchangeFilterFunction logRequest (SomeLogObject someLogObject) {
    return ExchangeFilterFunction.ofRequestProcessor(clientRequest -> {
        /**
         business logic for callback goes here
         */
        return Mono.just(clientRequest);
    });
}

//code for plugging in logRequest callback (at some othe place)
WebClient webClient = WebClient
        .builder()
        .clientConnector(new ReactorClientHttpConnector(HttpClient.from(tcpClient)))
        .baseUrl(baseURL)
        .filters(exchangeFilterFunctions -> exchangeFilterFunctions.add(logRequest(someLogObject)))
        .build();

webClient
        .get()
        .uri(uriBuilder -> uriBuilder.path("some_uri_path").queryParams(queryParam).build())
        .header("some_header_key", "some_header_value")
        .retrieve().bodyToMono(String.class);

Here the logRequest is triggered in beginning itself (much before the request is triggered). As per my debugging I found that it gets triggered when retrieve() is called.

Is there a way to ensure that logRequest gets triggered immediately before the request is sent and NOT when the mono is created?

Thanks in advance

I think you are looking for the following change:

ExchangeFilterFunction logRequest (SomeLogObject someLogObject){
    return ExchangeFilterFunction.ofRequestProcessor(clientRequest ->
            Mono.defer(() -> {
                /**
                 business logic for callback goes here
                 */
                return Mono.just(clientRequest);
            })
    );
}

Mono.defer() will delay code execution until the real request.