[Potential bug] Server Push not working after Tomcat restart

Hello everyone,

we are developing a web application with the latest Vaadin version with Spring Boot and Vaadin4Spring on a Tomcat 7.x server. We make use of the following Push configuration in our UI:

@Push(transport = Transport.LONG_POLLING, value = PushMode.AUTOMATIC) The issue we are facing is that sometimes, after starting up Tomcat, for the first client that connects to the web UI, the push support does not work. Attempting to use it will cause infinite loading and freeze the app for that client only. Refreshing the page resolves the issue. For me, this behaviour smells like a race condition in Vaadin Server or Atmosphere.

There are no errors in the web browser console (tested in IE11, Chrome and Firefox) and also no server-side errors. That, and the fact that it does not always occur reliably, makes it really hard for us to debug this error.

Any hints would be much appreciated. I can also provide more detailed information if required.

Kind regards,