SessionListener attempts to remove session from distributed storage

[jorgheymans]

In my attempts to isolate behaviour for https://vaadin.com/forum/t/continous-deployment-and-vaadin/167127/15 , I noticed that SessionListener attempts to delete the session from distributed storage during shutdown of the application. It fails to do so however as the Spring application context is closed by the time the listener is invoked.

I have 2 remarks on this:

• when the instance is shut down, and the user with said session cookie closes the browser before interacting with the application again, is associated session data in redis effectively orphaned ? (EDIT i guess this is described here Allow backend connector to apply expiration policies based on HTTP session timeout #126)
• why does the session need to be removed from redis here, as another application instance could resume serving the user and hence would need that session data to be present ?

Unable to delete data with key fe213d5a-198f-4719-a31f-de08fddef39d from distributed storage associated to session 9EA09A9E52C4FAF243F281FB4C85876D

java.lang.IllegalStateException: LettuceConnectionFactory was destroyed and cannot be used anymore
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.assertStarted(LettuceConnectionFactory.java:1447) ~[spring-data-redis-3.3.4.jar!/:3.3.4]
	at org.springframework.data.redis.connection.lettuce.LettuceConnectionFactory.getConnection(LettuceConnectionFactory.java:1045) ~[spring-data-redis-3.3.4.jar!/:3.3.4]
	at com.vaadin.kubernetes.starter.sessiontracker.backend.RedisConnector.deleteSession(RedisConnector.java:94) ~[kubernetes-kit-starter-2.2.2.jar!/:2.2.2]
	at com.vaadin.kubernetes.starter.sessiontracker.SessionListener.lambda$sessionDestroyed$0(SessionListener.java:104) ~[kubernetes-kit-starter-2.2.2.jar!/:2.2.2]
	at java.base/java.util.Optional.ifPresent(Optional.java:178) ~[na:na]
	at com.vaadin.kubernetes.starter.sessiontracker.SessionListener.sessionDestroyed(SessionListener.java:99) ~[kubernetes-kit-starter-2.2.2.jar!/:2.2.2]
	at org.apache.catalina.session.StandardSession.expire(StandardSession.java:629) ~[tomcat-embed-core-10.1.30.jar!/:na]
	at org.apache.catalina.session.StandardSession.expire(StandardSession.java:571) ~[tomcat-embed-core-10.1.30.jar!/:na]
	at org.apache.catalina.session.StandardManager.stopInternal(StandardManager.java:384) ~[tomcat-embed-core-10.1.30.jar!/:na]
	at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:231) ~[tomcat-embed-core-10.1.30.jar!/:na]
	at org.apache.catalina.core.StandardContext.stopInternal(StandardContext.java:4644) ~[tomcat-embed-core-10.1.30.jar!/:na]
	at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:231) ~[tomcat-embed-core-10.1.30.jar!/:na]
	at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1219) ~[tomcat-embed-core-10.1.30.jar!/:na]

[jorgheymans]

This can be fixed by setting server.servlet.session.persistent=true (as recommended by vaadin support), which makes the servlet container not destroy its sessions upon shutdown. It should be a mandatory setting when using kubernetes-kit.

[tamasmak]

This is the same exception using Hazelcast:

2025-09-05T16:08:49.232Z  INFO 1 --- [ionShutdownHook] o.s.b.w.e.tomcat.GracefulShutdown        : Commencing graceful shutdown. Waiting for active requests to complete
2025-09-05T16:08:49.241Z  INFO 1 --- [tomcat-shutdown] o.s.b.w.e.tomcat.GracefulShutdown        : Graceful shutdown complete
2025-09-05T16:08:49.306Z ERROR 1 --- [ionShutdownHook] c.v.k.s.sessiontracker.SessionListener   : Unable to delete data with key 3f4823c3-1357-4bba-92e8-c95259c5bd35 from distributed storage associated to session BA2F405A4B33E42B99EA439DA1603E44

com.hazelcast.core.HazelcastInstanceNotActiveException: Hazelcast instance is not active!
        at com.hazelcast.internal.serialization.impl.AbstractSerializationService.serializerFor(AbstractSerializationService.java:557) ~[hazelcast-5.5.0.jar!/:5.5.0]
        at com.hazelcast.internal.serialization.impl.AbstractSerializationService.toBytes(AbstractSerializationService.java:231) ~[hazelcast-5.5.0.jar!/:5.5.0]
        at com.hazelcast.internal.serialization.impl.AbstractSerializationService.toBytes(AbstractSerializationService.java:218) ~[hazelcast-5.5.0.jar!/:5.5.0]
        at com.hazelcast.internal.serialization.impl.AbstractSerializationService.toData(AbstractSerializationService.java:203) ~[hazelcast-5.5.0.jar!/:5.5.0]
        at com.hazelcast.map.impl.proxy.MapProxySupport.toDataWithStrategy(MapProxySupport.java:1351) ~[hazelcast-5.5.0.jar!/:5.5.0]
        at com.hazelcast.map.impl.proxy.MapProxyImpl.isLocked(MapProxyImpl.java:360) ~[hazelcast-5.5.0.jar!/:5.5.0]
        at com.vaadin.kubernetes.starter.sessiontracker.backend.HazelcastConnector.waitForSerializationCompletion(HazelcastConnector.java:92) ~[kubernetes-kit-starter-2.4.2.jar!/:2.4.2]
        at com.vaadin.kubernetes.starter.sessiontracker.backend.HazelcastConnector.deleteSession(HazelcastConnector.java:83) ~[kubernetes-kit-starter-2.4.2.jar!/:2.4.2]
        at com.vaadin.kubernetes.starter.sessiontracker.SessionListener.lambda$sessionDestroyed$0(SessionListener.java:104) ~[kubernetes-kit-starter-2.4.2.jar!/:2.4.2]
        at java.base/java.util.Optional.ifPresent(Unknown Source) ~[na:na]
        at com.vaadin.kubernetes.starter.sessiontracker.SessionListener.sessionDestroyed(SessionListener.java:99) ~[kubernetes-kit-starter-2.4.2.jar!/:2.4.2]
        at org.apache.catalina.session.StandardSession.expire(StandardSession.java:624) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.session.StandardSession.expire(StandardSession.java:566) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.session.StandardManager.stopInternal(StandardManager.java:384) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:235) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.core.StandardContext.stopInternal(StandardContext.java:4696) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:235) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1219) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1208) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at java.base/java.util.concurrent.FutureTask.run(Unknown Source) ~[na:na]
        at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at java.base/java.util.concurrent.AbstractExecutorService.submit(Unknown Source) ~[na:na]
        at org.apache.catalina.core.ContainerBase.stopInternal(ContainerBase.java:814) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:235) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1219) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1208) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at java.base/java.util.concurrent.FutureTask.run(Unknown Source) ~[na:na]
        at org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at java.base/java.util.concurrent.AbstractExecutorService.submit(Unknown Source) ~[na:na]
        at org.apache.catalina.core.ContainerBase.stopInternal(ContainerBase.java:814) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:235) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.core.StandardService.stopInternal(StandardService.java:468) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:235) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.core.StandardServer.stopInternal(StandardServer.java:915) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:235) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.apache.catalina.startup.Tomcat.stop(Tomcat.java:448) ~[tomcat-embed-core-10.1.40.jar!/:na]
        at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.stopTomcat(TomcatWebServer.java:301) ~[spring-boot-3.4.5.jar!/:3.4.5]
        at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.destroy(TomcatWebServer.java:374) ~[spring-boot-3.4.5.jar!/:3.4.5]
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.doClose(ServletWebServerApplicationContext.java:182) ~[spring-boot-3.4.5.jar!/:3.4.5]
        at org.springframework.context.support.AbstractApplicationContext.close(AbstractApplicationContext.java:1126) ~[spring-context-6.2.6.jar!/:6.2.6]
        at org.springframework.boot.SpringApplicationShutdownHook.closeAndWait(SpringApplicationShutdownHook.java:147) ~[spring-boot-3.4.5.jar!/:3.4.5]
        at java.base/java.lang.Iterable.forEach(Unknown Source) ~[na:na]
        at org.springframework.boot.SpringApplicationShutdownHook.run(SpringApplicationShutdownHook.java:116) ~[spring-boot-3.4.5.jar!/:3.4.5]
        at java.base/java.lang.Thread.run(Unknown Source) ~[na:na]

[tamasmak]

The Kubernetes Kit only tries to delete a session from the backend storage when it receives a notification that a session is about to be invalidated. This notification event happens when there is a HttpSession lifecycle change. Our SessionListener implements the jakarta.servlet.http.HttpSessionListener. Our intend with this was to remove the session when the HTTP session expires because of timeout or manual invalidation. It shouldn’t cause any problems if a session is deleted because it was invalidated. A new session will be created and the Kubernetes Kit will handle that.

What I see in this ticket is that this deletion happens also when a pod is shutdown or deleted:

SessionListener.sessionDestroyed()
 ↳ StandardSession.expire()
 ↳ StandardManager.stopInternal()
 ↳ StandardContext.stopInternal()
 ↳ ContainerBase.stopInternal()
 ↳ StandardService.stopInternal()
 ↳ StandardServer.stopInternal()
 ↳ Tomcat.stop()
 ↳ TomcatWebServer.destroy()
 ↳ ServletWebServerApplicationContext.doClose()
 ↳ AbstractApplicationContext.close()
 ↳ SpringApplicationShutdownHook.run()

1. Spring Boot triggers graceful shutdown

• The SpringApplicationShutdownHook is called because the JVM is shutting down or because Spring received a SIGTERM (typical in Kubernetes).
• Spring calls ApplicationContext.close(), which cascades down to stop the web server (Tomcat).

2. Tomcat starts shutting down

• Tomcat.stop() is invoked.
• This stops all Contexts (web applications) inside Tomcat.

3. Tomcat stops the StandardManager

• The StandardManager is responsible for managing HTTP sessions.
• When it is stopped, it expires all active sessions to ensure that session listeners (like SessionListener) can clean up resources.
• This is required by the Servlet specification — sessions must be expired when the web application is undeployed or the container is shutting down.

4. SessionListener is invoked

• Since a HttpSessionListener is registered, Tomcat calls sessionDestroyed() for each session being expired.
• The listener tries to delete session data from the backend storage.

Solution 1:
One solution could be to stop listening to the session destroy events and just to rely on the manually set session expiration policy, to let the backend storage to delete them after the expiration time. In case of this approach sessions would live longer on the backend storage, even if they are invalidated.

Solution 2:
To ensure the backend storage is shut down after Tomcat session destruction is complete.

• This could be achieved by a SmartLifecycle bean for Hazelcast/Redis with a lower phase number so it shuts down later than Tomcat.
• Or using a @PreDestroy hook that gracefully clears sessions before Hazelcast/Redis is destroyed.

Solution 3:
To catch and ignore the HazelcastInstanceNotActiveException/IllegalStateException and just rely on the manually set session expiration policy, to let the backend storage to delete the session after the expiration time in cases like this.