sibar9bit/stateless-tomcat

Showing how externalising the HTTP Servlet session into a database can work.

Getting started

pushd app
./gradlew docker
popd
docker-compose up

This should build the application, and create a docker environment with 3 instances of the application talking to a single MySQL database, and haproxy as a load-balancer in front of the apps.

http://localhost/ should give you the same session ID each time.

Kill an instance of the tomcat application; the session should continue to work.

Tests

zero-downtime deployment

1. have a client access the site to few times
2. only a single session should be created
3. Check the logs that a CleanupObject instance has been created
4. Sequentially stop and restart each app_x instance
5. client sessions aren't interrupted by this
6. wait for a minute or two for the sessions to expire
7. you should see valueUnbound events in the logs as CleanupObjects are purged

See zero-downtime-deployment.sh.

extended downtime

1. have a few clients access the site to create sessions
2. Check the logs that various CleanupObject instances have been created
3. stop all of the app_x instances to simulate extended downtime of the application / segfaults
4. wait for 2 minutes (session timeout is 1 minute)
5. start one or more of the app_x instances
6. after a minute or so, you should see valueUnbound events in the logs as CleanupObjects are purged

See extended-downtime.sh.

image session

1. have a client access the site a few times
2. only a single session should be created
3. request the image using the client session
   1. is the session loaded from the DB?
4. request the image using no session cookie (replicating a cookie-less domain)
   1. is the session loaded from the DB?

See image-session.sh.