SpringCloud处理Websocket消息过长自动断开连接

SpringCloud处理Websocket消息过长自动断开连接

问题描述

近期实现了客户端订阅Websocket后，服务端定期向客户端推送相关设备消息的功能，在本地测试没有问题，上线后却发现订阅设备数量超过一定数量后Websocket就会自动断开连接

报错日志

java.lang.IllegalStateException: Message will not be sent because the WebSocket session has been closed
	at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.writeMessagePart(WsRemoteEndpointImplBase.java:449) ~[tomcat-embed-websocket-9.0.79.jar:9.0.79]
	at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:307) ~[tomcat-embed-websocket-9.0.79.jar:9.0.79]
	at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendMessageBlock(WsRemoteEndpointImplBase.java:249) ~[tomcat-embed-websocket-9.0.79.jar:9.0.79]
	at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendString(WsRemoteEndpointImplBase.java:191) ~[tomcat-embed-websocket-9.0.79.jar:9.0.79]
	at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendObject(WsRemoteEndpointImplBase.java:614) ~[tomcat-embed-websocket-9.0.79.jar:9.0.79]
	at org.apache.tomcat.websocket.WsRemoteEndpointBasic.sendObject(WsRemoteEndpointBasic.java:72) ~[tomcat-embed-websocket-9.0.79.jar:9.0.79]
	at tbea.websocket.SubscribeDeviceParamWebSocketServer.lambda$scheduleMessagePush$2(SubscribeDeviceParamWebSocketServer.java:305) ~[classes/:na]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[na:1.8.0_301]
	at java.util.concurrent.FutureTask.runAndReset$$$capture(FutureTask.java:308) ~[na:1.8.0_301]
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java) ~[na:1.8.0_301]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180) ~[na:1.8.0_301]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294) ~[na:1.8.0_301]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_301]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_301]
	at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_301]

问题排查

经过排查发现当Websocket服务段推送消息数据大小在50kb左右时功能正常，此时再增加订阅一个设备时，线上Websocket就会自动断开连接，这时候很容易想到可能是Websocket推送消息可能又大小限制，当消息超过64kb的时候可能会自动断连。

然而我在本地测试发现消息数据大小远远超过64kb，仍然没有断连，客户端依旧可以收到消息。

这时发现我本地测试时，直接调用的是提供该功能服务的端口，而线上调用的是网关(gateway)，再次测试发现，通过网关订阅Websocket时消息数据大小超过64kb时确实会自动断连。

解决方法

知道问题原因之后，直接通过搜索引擎发现Spring Cloud Gateway可以通过spring.cloud.gateway.httpclient.websocket.max-frame-payload-length配置来修改消息体的大小限制

修改gateway配置文件如下：

spring:
  cloud:
    gateway:
      httpclient:
        websocket:
          # websocket数据包最大字节数
          max-frame-payload-length: 6553600

修改配置文件后，重新部署gateway发现功能正常。