java - Websocket 阻塞，不会因客户端拔出/断电而超时

Question

我的 Tomcat + Spring websocket 应用程序有一个奇怪的问题。当用户由于断电或拔出插头而在没有发送“关闭”信号的情况下断开连接时，线程将在大约 10 秒后阻塞。

线程在此函数上阻塞:

org.springframework.web.socket.WebSocketSession.sendMessage(WebSocketMessage<?> wsm) throws IOException;

我尝试在 AppConfig 中添加一行来尝试设置 3 秒的超时，但它似乎无法正常工作，因为 block 似乎在抛出异常之前持续了 15 分钟以上。

@Bean(name="servletServerContainerFactoryBean")
public int maxSessionIdleTimeout() {
  return 3000;
}

这是最终 SocketTimeoutException 后的堆栈跟踪

Step: 2304
SendB -> test isOpen -> sendMes -> Done -> Finished Send.
SendB -> test2 isOpen -> sendMes -> User closed connection during packet sending: s01
Propogating exception up!
java.io.IOException: java.net.SocketTimeoutException
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:315)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:250)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendPartialString(WsRemoteEndpointImplBase.java:223)
    at org.apache.tomcat.websocket.WsRemoteEndpointBasic.sendText(WsRemoteEndpointBasic.java:49)
    at org.springframework.web.socket.adapter.standard.StandardWebSocketSession.sendTextMessage(StandardWebSocketSession.java:197)
    at org.springframework.web.socket.adapter.AbstractWebSocketSession.sendMessage(AbstractWebSocketSession.java:102)
    at org.infpls.noxio.game.module.game.session.NoxioSession.sendPacket(NoxioSession.java:40)
    at org.infpls.noxio.game.module.game.dao.lobby.GameLobby.step(GameLobby.java:117)
    at org.infpls.noxio.game.module.game.dao.lobby.GameLobby$GameLoop.run(GameLobby.java:274)
Caused by: java.net.SocketTimeoutException
    at org.apache.tomcat.websocket.server.WsRemoteEndpointImplServer.doWrite(WsRemoteEndpointImplServer.java:81)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.writeMessagePart(WsRemoteEndpointImplBase.java:494)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:309)
    ... 8 more
## CRITICAL ## Ejecting player: test2 :: Exception thrown on packet send...
java.io.IOException: java.net.SocketTimeoutException
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:315)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:250)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendPartialString(WsRemoteEndpointImplBase.java:223)
    at org.apache.tomcat.websocket.WsRemoteEndpointBasic.sendText(WsRemoteEndpointBasic.java:49)
    at org.springframework.web.socket.adapter.standard.StandardWebSocketSession.sendTextMessage(StandardWebSocketSession.java:197)
    at org.springframework.web.socket.adapter.AbstractWebSocketSession.sendMessage(AbstractWebSocketSession.java:102)
    at org.infpls.noxio.game.module.game.session.NoxioSession.sendPacket(NoxioSession.java:40)
    at org.infpls.noxio.game.module.game.dao.lobby.GameLobby.step(GameLobby.java:117)
    at org.infpls.noxio.game.module.game.dao.lobby.GameLobby$GameLoop.run(GameLobby.java:274)
Caused by: java.net.SocketTimeoutException
    at org.apache.tomcat.websocket.server.WsRemoteEndpointImplServer.doWrite(WsRemoteEndpointImplServer.java:81)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.writeMessagePart(WsRemoteEndpointImplBase.java:494)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:309)
    ... 8 more
Finished Send. Step Finished.

线程一次被阻塞 15 分钟是一个主要问题。任何有关为什么会发生这种情况以及如何解决它的信息将不胜感激。谢谢!

Answer 1

终于找到答案了。这实际上是一个系统设置。

Source

How many times to retry before deciding that something is wrong and
it is necessary to report this suspicion to network layer. Minimal RFC
value is 3, it is default, which corresponds to  3sec-8min depending on
RTO.
/proc/sys/net/ipv4/tcp_retries2