Yesterday I got a trial account on webhosting.net's Jelastic v2.2.2 and configured an environment with a minimum of 0 cloudlets (max 8, i.e., all dynamic, no reserved). Then I deployed a Grails war which was using 3 cloudlets after it started up (around 350 MB). It worked great, and I was very impressed.
However, I did not access my app overnight, and the billing history shows it kept using 3 dynamic cloudlets every hour, even with 0 requests (i.e., 0 MB paid traffic) for 14 hours. Is there some way I can get my Jelastic environment to sleep (i.e., hibernation) after some period with no requests (e.g., after an hour or two)? Then, when it gets a request, I'd like it to automatically wake up (i.e., allocate some cloudlets and restore memory from disk). I see how to stop and restart it manually, but I would like it to work automatically, for any requester.
edit: I found the following documentation, but does it not work for Tomcat/Grails?
Hibernation
Jelastic’s hibernation feature delivers even better utilization of cluster resources. Optimal use of resources is achieved by suspending non-active containers and returning released resources back to the cluster.
Because they are in sleep mode, hibernated containers do not consume resources (only disk space). As a result you save money while your containers are in hibernate mode. If applications are needed again the platform returns them to a running state again in just a few seconds.
It takes a little time to awaken your environment from sleep, so it's not suitable to work how you describe for production use - you would effectively lose visitors because it would seem like your service is offline due to the delays for that first access.
For that reason the 'sleep' function is only active for trial accounts, and the inactivity time before sleep is set by the hosting provider (so you should contact them directly for help on that point).
Of course you should also remember that accesses from search engine spiders etc. may keep your environment awake.