Endpoint takes too much time to send the response - spring

Question

I have a problem using Spring WebFlux. Actually my project is composed by
Api wrapper ( basically code that uses WebClient to call a remote service)
private final BinanceServerTimeApi binanceServerTimeApi;
private final WebClient webClient;
#Value("${binance.api.secret}")
private String secret;
#Autowired
public BinanceAccountApi(#Value("${binance.api.baseurl}") String baseUrl,
#Value("${binance.api.key}") String key,
BinanceServerTimeApi binanceServerTimeApi) {
this.binanceServerTimeApi = binanceServerTimeApi;
this.webClient = WebClient.builder()
.baseUrl(baseUrl)
.defaultHeader("X-MBX-APIKEY",key)
.build();
}
public Mono<AccountInformation> getAccountInformation() {
Mono<ResponseServerTime> responseServerTime = binanceServerTimeApi.getServerTime();
String apiEndpoint = "api/v3/account?";
String queryParams = "recvWindow=50000&timestamp=" + responseServerTime.block().getServerTime();
String signature = HmacSHA256Signer.sign(queryParams, secret);
String payload = apiEndpoint+queryParams+"&signature="+signature;
log.info("final url for getAccountInformation is {}", payload);
return this.webClient.get().uri(payload).accept(MediaType.APPLICATION_JSON)
.retrieve().bodyToMono(AccountInformation.class).log();
}
the endpoint used by my javascript client
#Autowired
private BinanceAccountApi binanceAccountApi;
public Mono<ServerResponse> getAccountPortfolio(ServerRequest request) {
return binanceAccountApi.getAccountInformation()
.flatMap(accountInformation -> ServerResponse.ok()
.contentType(MediaType.APPLICATION_JSON)
.body(fromObject(accountInformation))).log();
}
Here my main class
#Bean
public RouterFunction<ServerResponse> route(AccountHandler handler) {
return RouterFunctions .route(GET("/route/accountInformation").and(accept(MediaType.APPLICATION_JSON)),handler::getAccountPortfolio);
}
When I hit a get to this route /route/accountInformation, the first call works fine but the others call are pending (the server never sends the response).
Note that the first call to the endpoint lasts for 2000 ms.
This is my first approach to the WebFlux project and I am trying to figure out how it works.

Answer 1

Without more information it's hard to tell what's happening (the output of your log operator should help here). But using the block operator right in the middle of your handler is suspicious; by doing that, you might be blocking one of the few server threads.
Try something like:
return binanceServerTimeApi.getServerTime().flatMap(responseServerTime -> {
// ...
return this.webClient.get().uri(payload).accept(MediaType.APPLICATION_JSON)
.retrieve().bodyToMono(AccountInformation.class).log();
});
This will chain operations in a non-blocking way. If the situation doesn't improve after that, try adding a few log operators to understand where time is spent.