启用permessage-deflate后Undertow发送WebSocket消息损坏问题

运行环境：Undertow 2.3.5.Final，OpenJDK 11.0.22（2024-01-16）
功能：实现一个发送光标位置的WebSocket服务器

问题现象 #

打开两个标签页连接服务器后，客户端最终会收到损坏的消息：

• 成功消息示例：

{"op":"refresh-presence","room-id":"123","data":{"5c494daf-3c68-4ef6-b649-69177cc10105":{"peer-id":"5c494daf-3c68-4ef6-b649-69177cc10105","user":null,"data":{}},"b4eb6d8a-562a-4b8c-8e44-ecd43cba3621":{"peer-id":"b4eb6d8a-562a-4b8c-8e44-ecd43cba3621","user":null,"data":{}},"88f03150-696d-4e09-afbd-1381a2fa2f7e":{"peer-id":"88f03150-696d-4e09-afbd-1381a2fa2f7e","user":null,"data":{"cursors-space-default--main-123":{"x":723,"y":345,"xPercent":56.484375,"yPercent":52.43161094224924}}}}}

• 损坏消息示例1（头部截断+字段值被UUID污染）：

ors-space-default--main-123":{"x":562,"y":12,"xPercent":43.9ab521,"r56nt":1b3273a68bf-fefe7d735"}

• 损坏消息示例2（UUID字段截断）：
  成功消息：

{"op":"set-presence-ok","room-id":"123","client-event-id":"9093a7cc-96ea-42e5-943e-e7c7962bbfcc"}

损坏消息：

{"op":"set-presence-ok","room-id":"123","client-event-id":"6186021","u44-45ser"265-211b8cu44315"}

配置代码 #

WebSocket连接设置（Clojure） #

(defn ws-request [^HttpServerExchange exchange ^IPersistentMap headers ^WebSocketConnectionCallback callback]
  (let [handler (->  (WebSocketProtocolHandshakeHandler. callback)
                     (.addExtension (PerMessageDeflateHandshake.
                                     true ; client? 
                                     6    ; deflaterLevel: is a number from 0 (no compression) to 9 (maximum compression)
                                     )))]
    (when headers
      (set-headers (.getResponseHeaders exchange) headers))
    (.handleRequest handler exchange)))

消息发送代码（Clojure） #

(defn send-json!
  "Serializes `obj` to json, and sends over a websocket."
  [obj ws-conn]
  (let [obj-json (->json obj)
        p (promise)
        _ (WebSockets/sendText
           ^String obj-json
           ^WebSocketChannel ws-conn
           (proxy [WebSocketCallback] []
             (complete [ws-conn context]
               (deliver p nil))
             (onError [ws-conn context throwable]
               (deliver p throwable))))
        ret @p]
    (when (instance? Throwable ret)
      (throw ret))))

潜在原因定位 #

移除PerMessageDeflateHandshake压缩扩展后，消息损坏问题不再复现。但目前无法确定该扩展的具体问题点，寻求技术解决方案。

内容的提问来源于stack exchange，提问作者Stepan Parunashvili