Java 11: Problems with Asynchronous REST Calls in Spring Boot Returning Empty Response
I'm deploying to production and I'm dealing with This might be a silly question, but This might be a silly question, but I'm working on a personal project and I'm working on a Spring Boot application that makes asynchronous REST calls using WebClient in Java 11... However, I'm working with an scenario where the response from my REST API calls is sometimes empty, even though the API itself returns a valid response. The method making the API call looks like this: ```java import org.springframework.web.reactive.function.client.WebClient; import reactor.core.publisher.Mono; public class ApiService { private final WebClient webClient; public ApiService(WebClient.Builder webClientBuilder) { this.webClient = webClientBuilder.baseUrl("http://api.example.com").build(); } public Mono<MyResponse> fetchData() { return webClient.get() .uri("/data") .retrieve() .bodyToMono(MyResponse.class); } } ``` When I call `fetchData()` from a controller method, the response is often an empty object, like this: ```java @GetMapping("/get-data") public ResponseEntity<MyResponse> getData() { MyResponse response = apiService.fetchData().block(); return ResponseEntity.ok(response); } ``` On inspecting the logs, I see the following behavior intermittently: ``` 2023-03-15 10:00:00 behavior 1234 --- [reactor-http-nio-1] o.s.web.reactive.function.client.ExchangeFunctions : 500 Server behavior for "http://api.example.com/data" ``` I suspect that it could be a timing scenario with the reactive stream, as multiple requests are being made quite rapidly. I've tried adding `subscribeOn(Schedulers.boundedElastic())` to the `fetchData()` method, but it hasn’t resolved the scenario. Additionally, I’m using Spring Boot 2.5.4 and I’ve verified that the API endpoint returns the expected data when accessed directly via a browser or Postman. Could this be related to how the reactive streams are being handled? Are there specific best practices for making asynchronous calls with Spring WebClient that I might be missing? Any advice on how to debug this further would be greatly appreciated! For context: I'm using Java on Windows. What am I doing wrong? For context: I'm using Java on Ubuntu. What am I doing wrong? For context: I'm using Java on Ubuntu. Has anyone else encountered this? I'm working with Java in a Docker container on macOS. What's the best practice here?