[undertow-dev] JSR WebSocket onMessage called out-of-order

Hi, I ran into an issue with the Undertow JSR WebSocket implementation: the message handler's @OnMessage method is not called with messages in the same order as these were sent. I encountered this problem first with the current WildFly 8.2.0.Final version. I posted about it in the forums [1]. But since I got no replies there and can reproduce this problem with Undertow 1.2.0.Beta4 (from maven) alone, I thought this might be the right place to ask about it. I am developing a @ServerEndpoint which needs to handle clients sending unfragmented messages in rapid succession. These messages are not always delivered in the order as they were sent. Since WebSocket is based on HTTP, I assume that the messages arrive in the "correct" order at the server. However, from time to time two messages appear switched (e.g. message no. 4 arrives at @OnMessage before message no. 3). If I fragment the messages (according to RFC 6455), the order of all messages is always correct. I have uploaded an example application which reproduces this to http://pastebin.com/tcm6ZnsB It uses some Guava classes for checking the order of messages. I can also reproduce this problem with another (non-public but RFC compliant) WebSocket library. My first question is, if that is intended behavior or a bug? The WebSocket RFC does not explicitly forbid this kind of behavior, however for me it was very surprising given that 1. the underlying protocols deliver everything in order, 2. this works as I expected it for fragmented messages and 3. I haven't seen this for other implementations. If this is not considered a bug, is there an option which basically forces in-order delivery of messages? Ideally even accessible in WildFly. If not, does opening a feature request for this make sense (i.e. does it have a realistic chance of being addressed)? Best, Stephan [1]: https://developer.jboss.org/message/921226#921226 -- Stephan Mehlhase Email: stephan.mehlhase(a)eml.org EML European Media Laboratory GmbH Schloss-Wolfsbrunnenweg 35 69118 Heidelberg Amtsgericht Mannheim / HRB 335719 Managing Partner: Dr. h. c. Dr.-Ing. E. h. Klaus Tschira, Scientific and Managing Director: Prof. Dr.-Ing. Andreas Reuter http://www.eml.org