Flux.create() not generating events - spring

Question

I'm trying to use Flux to generate asynchronous server sent events using Flux.create. When my client connects the request eventually times out with no event ever received. I hard-coded in an event to be sent by the Flux.create just to see data flow, but still nothing received client side.
#GetMapping(path = "/stream", headers = "Accept=*/*", consumes = MediaType.ALL_VALUE, produces = MediaType.TEXT_EVENT_STREAM_VALUE)
public Flux<ServerSentEvent<PricingDTO>> getEventStream() {
final Flux<ServerSentEvent<PricingDTO>> flux = Flux.<ServerSentEvent<PricingDTO>>create(emitter -> {
final PricingDTO pricing = new PricingDTO();
pricing.setId(99L);
emitter.next(ServerSentEvent.builder(pricing).build());
});
return flux;
}
Client side (Angular) code:
const eventSource = new EventSource(url);
eventSource.onmessage = (event) => {
console.debug('Received event: ' + event);
const json = JSON.parse(event.data);
// Should be PricingDTO record here
};
eventSource.onerror = (error) => {
if (eventSource.readyState === EventSource.CLOSED) {
console.log('The stream has been closed by the server.');
eventSource.close();
} else {
console.log('Error here: ' + error);
}
};
I never see an event come through the EventSource. Eventually the request times out and I see the error: net::ERR_EMPTY_RESPONSE
I'm new to using WebFlux and I suspect I'm missing some initialization on the FluxStream before I return the Flux result. I have debugged and do see the request being received by my web service and the Flux object being returned. Any idea why I'm not receiving my events?

Answer 1

Your webflux code seems fine. I tested this with the following simplified example (without your custom classes).
#SpringBootApplication
#RestController
public class App {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
#GetMapping(path = "/stream", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
public Flux<String> getEventStream() {
return Flux.create(emitter -> emitter.next("hi").next("hi2"));
}
}
When connecting to the steam in chrome you get to see the events coming in just fine:
data:hi
data:hi2
the problem either lies in your accept header filter, or on the client side. You could ofcourse validate this by connecting to your stream in a browser (or better, a test)