Detach- Event on idle session not fired on missing heartbeats

General
1

Hi all,
I’m struggling with catching the detach events for idle sessions to clean some cache. I’m using V7.0.4
I followed the guidance in the BOV at https://vaadin.com/book/vaadin7/-/page/application.lifecycle.html
and the wiki at https://vaadin.com/wiki/-/wiki/Main/Cleaning+up+resources+in+an+UI

The web.xml configuration parameters ‘heartbeatInterval’ and closeIdleSessions (true) are likely set correct:


<servlet>
		<servlet-name>UIApplication</servlet-name>
		<servlet-class>...
           <init-param>
            <param-name>heartbeatInterval</param-name>
            <param-value>20</param-value>
     	   </init-param>
        
          <init-param>
        	<param-name>closeIdleSessions</param-name>
    		<param-value>true</param-value>
        </init-param>
	</servlet>

which shows a request to the session parameters in the UI: getSession().getConfiguration().getHeartbeatInterval() (=20sec)/ isCloseIdleSessions() (=true).

I call my application in Firefox and follow the heartbeats with the httpFox- tracer add-on. Perfect !
I change the URL to ‘about:blank’ and the heartbeats vanish ! Perfect !

I wait 3 heatbeat intervalls and … nothing happens.

My app is as simple as can be:


...
public class SimpleiUI extends UI implements DetachListener{

	protected void init(VaadinRequest request) {

		final VerticalLayout layout = new VerticalLayout();
		layout.setMargin(true);
		setContent(layout);

		addDetachListener(this);
		
		System.out.println("UI-IdleTimeout: " + getSession().getConfiguration().getHeartbeatInterval() + ",IdleClean:"+ getSession().getConfiguration().isCloseIdleSessions() );
	}

	@Override
	public void detach(DetachEvent event) {
		System.out.println ("Detach listener");
		
	}
}

I’m lost, where is my misunderstanding ?

Thanks for any help !
Gerd