WebSocketSession#close never emit when using ReactorHttpServer [SPR-17306]

[spring-projects-issues]

Sola opened SPR-17306 and commented

Given the following handler snippet,

@Override
public Mono<Void> handle(WebSocketSession session) {
  return session.send(Flux.error(new Throwable())
      .onErrorResume(e -> session.close(CloseStatus.GOING_AWAY))
      .then(Mono.empty()));
}

when using ReactorHttpServer, the Mono from session#close never emit.
!image-2018-09-27-05-12-22-853.png|thumbnail!

---

Affects: 5.0.9

Attachments:

• image-2018-09-27-05-12-22-853.png (121.37 kB)

Referenced from: commits 42b7c5a, b462ca2, bf4d00c, 1320fed

Backported to: 5.0.11

[spring-projects-issues]

Rossen Stoyanchev commented

I can confirm the issue and investigating. In the mean time as a workaround, make the "send" and the "close" sequential (and not nested), e.g.:

@Override
public Mono<Void> handle(WebSocketSession session) {

  Flux<WebSocketMessage> output = Flux.error(new Throwable())
      .onErrorResume(e -> Flux.empty())
      .cast(WebSocketMessage.class);

  return session.send(output)
    .then(Mono.defer(() -> session.close(CloseStatus.GOING_AWAY)));
}

[spring-projects-issues]

Rossen Stoyanchev commented

I've confirmed the issue with Reactor Netty only, and created reactor/reactor-netty#444.

[spring-projects-issues]

Rossen Stoyanchev commented

The actual fix should come from Reactor but I'm turning this into a task and keeping it open and scheduled for the next set of releases. Depending on the outcome of the Reactor Netty ticket, we may have some follow-up to do here.

[spring-projects-issues]

Rossen Stoyanchev commented

Moving to 5.x.backlog while waiting for the Reactor Netty fix.

[spring-projects-issues]

Sola commented

According to your workaround, what if I have to send the corresponding CloseStatus base on what Exception I got?

For example:

userPrincipal.flatMap { principal ->
    userService.fetchUserInfo(principal)
        .onErrorResume { e ->
            logger.error("Failed to fetch user's info", e)
            close(CloseStatus.SERVER_ERROR.withReason(e.message!!)).then(Mono.empty())
        }
}.switchIfEmpty(close(CloseStatus.NOT_ACCEPTABLE.withReason("Unauthorized.")).then(Mono.empty()))

[spring-projects-issues]

Rossen Stoyanchev commented

SolaDev, a fix is coming to Reactor Netty. 

[spring-projects-issues]

Rossen Stoyanchev commented

This is now fixed in Reactor Netty and will be in 0.7.11 (Bismuth SR13) and 0.8.2 (Californium SR2). There are corresponding changes in the Spring Framework to make use of the new sendClose available in NettyWebsocketOutbound.