WebSocketGraphQlTransport does not emit error signal if connection closed before GraphQL session is initialized

[AliakseiKakora]

I use spring-graphql 1.3.1 as part of spring-boot-starter-graphql. I want to create a GraphQL subscription to the server which does not belong to me (means I can not do anything on server side to solve my issue). This is how I create subscription and handle events

    WebSocketClient client = new ReactorNettyWebSocketClient(HttpClient.create(),
            () -> WebsocketClientSpec.builder().maxFramePayloadLength(256 * 1024));

    String url = configs.getWsUrl();
    WebSocketGraphQlClient graphQlClient = WebSocketGraphQlClient
            .builder(url, client)
            .keepAlive(Duration.ofSeconds(10))
            .interceptor(new GraphQlClientInterceptor(configs))
            .build();

    Flux<ClientGraphQlResponse> clientGraphQlResponseFlux = graphQlClient
            .document(getQuery(configs))
            .executeSubscription();

    AtomicReference<String> offset = new AtomicReference<>(configs.getOffset());
    Disposable disposable = clientGraphQlResponseFlux
            .map(data -> data.toEntity(BusinessEvent.class))
            .doOnError(error -> {
                log.error("Error in subscription");
            })
            .subscribe(message -> {
                //business logic
            });

And this is how I send Auth token - as part of connection_init payload in the GraphQlClientInterceptor

public class GraphQlClientInterceptor implements WebSocketGraphQlClientInterceptor {

private final SubscriptionManagement configs;

/**
 * Create payload property data. Connection Init is in following format
 * <pre>
 * {
 *   "id": "{GUID}"
 *   "type": "connection_init",
 *   "payload": {
 *     "Authorization": "Bearer {OAUTH TOKEN}
 *     "x-app-key": "{APPLICATION KEY}"
 *   }
 * }<pre/>
 */
@Override
public Mono<Object> connectionInitPayload() {
    Map<String, String> payload = Map.of(
            "x-app-key", configs.getAppKey(),
            "Authorization", configs.getAuthorization()
    );
    return Mono.just(payload);
}

}

In general it works fine - I'm able to connect to the server and process messages. Once some errors occurs I'm able to handle them as well.

But when I started testing flow with invalid auth credentials - the error was not throw to my handler (means doOnError()). I see just log message like this -

"GraphQlSession over ReactorNettyWebSocketSession[id=2127633d, uri=wss://my-url] disconnected with CloseStatus[code=4401, reason=Unauthorised - Invalid credentials]".

Based on my investigation - WebSocketGraphQlTransport tries to terminate request. But at the time when connection_init payload send (and was rejected because of invalid auth token) there no connection yet. Similar issue happens when connection timeout error occurs. In my understanding the issue is - when error occurs on the connection_init phase I do not receive any Errors in the Flux. I'm looking a way to be able to handle any issues that occurs during subscription lifecycle. I would appreciate any help here.

[rstoyanchev]

In this case the server closes the connection before the GraphQL session is initialized, so at the point where you've been debugging, the transport should be emitting an error on the session sink, but it isn't. I will schedule this for a fix.