I wrote myself a server monitoring utility using Vaadin 18.0.2 for the UI. This works very nicely execpt for one major issue:
The monitoring is meant to become part of our "team-screen", i.e. a big screen displaying team news, build results, server status, etc.). As such the application has be able to run for longer periods without any user interaction.
The application once per minute queries a bunch of servers re. livelihood and response times and then updates a corresponding result screen. For some reason it always crashes after pretty reproducibly 80 minutes with a com.vaadin.flow.component.UIDetachedException:
com.vaadin.flow.component.UIDetachedException: null
at com.vaadin.flow.component.UI.handleAccessDetach(UI.java:412)
at com.vaadin.flow.component.UI.access(UI.java:512)
at com.vaadin.flow.component.UI.access(UI.java:499)
...
Once this happens all subsequent UI updates have the same issue, i.e. the display "freezes".
The above code is called by a listener which always first requests a Vaadin UI handle and then updates the screen. While it keeps getting such a UI there obviously something's wrong with it after these 80 minutes and then - while the application's monitoring core continues to run - all UI updates are impossible. Neither reloading the page in the browser or even terminating and restarting the browser helps. The application's web-interface is "dead" after that and only an application restart can revive it. This is of course a complete killer or "no-go" for this kind of application. :-(
I suspect that there is some session timeout or UI object duration limit being reached but I haven't encountered any setting to control that so far. I also found no docs mentioning that some token or handle or similar needs to be regularly refreshed or so.
What I specifically don't understand is, why a browser page reload or even a browser restart doesn't help here. One doesn't get a login-in screen as one might expect if some token or session cookie would have expired or so, but the application's web interface is completely "dead" after that time. One doesnt even get any response anymore from the server but the browser requests just time out...
Any hint or guidance what could be the cause for these exceptions or what mechanism is behind this behavior?