Facing io.netty.handler.timeout.ReadTimeoutException: null while consuming server sent events

Question

I am new to spring web flux, I have a client application that consumes server-sent events, The events are published by the server randomly there is not fixed delay. But consumer throws io.netty.handler.timeout.ReadTimeoutException: null after 60 secs if there no event

Server-side events consumer code

webClient.get()
        .uri("http://localhost:8080/events")
        .accept(MediaType.TEXT_EVENT_STREAM)
        .retrieve()
        .bodyToFlux(type)
        .subscribe(event -> process(event));

I need the client to be connected even if there is no event for a long time.

Full Exception

[36mr.netty.http.client.HttpClientConnect   [...] The connection observed an error

io.netty.handler.timeout.ReadTimeoutException: null

reactor.Flux.MonoFlatMapMany.1    onError(org.springframework.web.reactive.function.client.WebClientRequestException: nested exception is io.netty.handler.timeout.ReadTimeoutException)
reactor.Flux.MonoFlatMapMany.1     

org.springframework.web.reactive.function.client.WebClientRequestException: nested exception is io.netty.handler.timeout.ReadTimeoutException
    at org.springframework.web.reactive.function.client.ExchangeFunctions$DefaultExchangeFunction.lambda$wrapException$9(ExchangeFunctions.java:141) ~[spring-webflux-5.3.5.jar:5.3.5]
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):

Answer 1

Webflux use a default timeout fallback that will eventually show io.netty.handler.timeout.ReadTimeoutException: null. It is possible to prevent this error by passing a custom timeout fallback to the timeout method(s):

public final Flux<T> timeout(Duration timeout, @Nullable Publisher<? extends T> fallback);

Additionally, you can use methods like onErrorContinue, onErrorReturn, ... to properly handle exceptions in Flux, example:

return webClient.get().uri(url).retrieve().bodyToFlux(String.class)
    .timeout(timeout, Mono.error(new ReadTimeoutException("Timeout")))
    .onErrorContinue((e, i) -> {
        // Log the error here.
    });

If you want to disable all these logs by default it is possible adding this line into file application.properties:

logging.level.reactor.netty.http.client.HttpClient=OFF

Answer 2

In my case the problem was the HttpClient response timeout, I just increased it

HttpClient.create(...).responseTimeout(Duration.ofMillis(5000));