Comments on: The new ehcache server

By: Greg Luck

Greg Luck — Sat, 02 Aug 2008 12:52:40 +0000

Adam
I have run ehcache in a 64 bit JDK with a 6GB heap for about 4 years now. I know of people out there running 15GB heaps.
Garbage collection can be very bad with large heaps. On my blog I have some magic settings I got from Sun which seem to work very well for avoiding Full GC pauses. I needed them for our app, which had a lot of cache churn.
I was surprised that the guy using 15GB did not need any special settings and did not have pauses.
So, I think it depends on your app. If you get into trouble try the settings I have. See http://gregluck.com/blog/archives/2006/07/how_we_solved_o.html
I am expecting people using the cache server to be running multi gigabyte caches.

By: Adam Malter

Adam Malter — Fri, 01 Aug 2008 03:30:25 +0000

Maybe you guys can solve a bit of a technical riddle I’ve had running around my head regarding cache implementations and java.. In our application we have a variety of in process cache’s and are now exploring off process and off machine caching.
With the in process caching, we are running hard against the 32bit heap memory limits. We are planning on migrating over to 64bit JVM instances, *but*, everywhere I turn I hear dread warnings of GC interactions with 2GB+ heaps. In fact, one learned developer I follow suggested to never use a 64bit JVM for a cache server, and instead load balance however many 32bit instances it takes to get to your desired cache size. (Specifically saying that even if you had to run dozens of instances on a single box, it was worth it vs a single large heap 64bit VM)
So, I guess the question is, how does ecache, specifically the server version, handle cache sizes of 2,4,8 or more GB’s. Does it use any fancy memory tricks to help avoid killer GC pauses etc.
I was doing a thought experiment and maybe thought that using ASM or CGLIB (and an absurdly high permgen size), one could compile survivor cache entries into class bytes and push them into Perm space, essentially cloning a malloc/free in java.
Anyway, sorry for rambling on your blog, this is really, really awesome stuff. Thanks very much for pushing java scalability to it’s limits. You all rawk!!
-A

By: Greg Luck

Greg Luck — Tue, 29 Jul 2008 11:37:59 +0000

Hi Anjan/Paul
Ehcache is already integrated with Terracotta. I worked with the Terracotta guys and made some changes to ehcache. They created a simple config. You can use Ehcache with replication handled by Terracotta.
As to a bundling it with the server, Terracotta is one of three replication choices with ehcache. And I am adding JMS in the next few months as a fourth option. I would rather leave it to the end user to configure their preferred replication scheme.

By: anjan bacchu

anjan bacchu — Tue, 29 Jul 2008 11:32:28 +0000

hi greg,
Good luck with this.
I’m also going through the same REST book. will be working on a JBoss related project with REST.
distributed ehcache : How about making a bundle with Terracotta + Glassfish ?
Thank you,
BR,
~A

By: Paul Davis

Paul Davis — Tue, 29 Jul 2008 11:06:38 +0000

Now, imagine several instances (behind the load balancer) running on terracotta servers with a shared heap…..