I have been testing Atmosphere on WAS Liberty, and it is all working fine on Liberty 8.5.5.4.
When I try to upgrade to Liberty 8.5.5.5 or 8.5.5.6, there is a 1 min delay on the initial connection.
The problem can be easily replicated by downloading the atmosphere-chat-2.3.3.war from maven central. Rename to atmosphere-chat.war, change the application.js to have transport = 'long-polling'. Copy modified war in liberty dropins folder. Start server, go to http://localhost:9080/atmosphere-chat/
I think this might be a bug with async processing in Liberty, but maybe the Atmosphere or IBM guys know better. I can't quite figure it out, so I am staying on 8.5.5.4 for now.
If anyone can shed some light. It would be great.
Setting
AtmosphereConfig.PROPERTY_USE_STREAM=false
works around the issue for now.