Using ehcache in front of memcached

Question

We have a web application that loads a User object from database. Its a high volume application with thousands of concurrent users so we're looking at ways to cache the User objects to minimise database load.

Currently using ehcache but are looking at memcached to lower the memory requirements of the application, and make it more scaleable.

Problem we are currently having with using memcached is the cpu load that serializing the User instance brings. We're looking at ways to speed up the serialization, but ar also considering if we could use a smaller ehcache cache backed by memcached server.

Has anyone had any experience using ehcache backed by memcached (ie. first look in ehcache, if user not there, look in memcache, if not there look in database)?

Any downsides to this kind of approach?

Answer 1

If you're willing to move away from Ehcache, you could consider Infinispan, which now includes integration with memcache. It's a bit more of a faff to get working than Ehcache, but not too much.

Starting with version 4.1, Infinispan distribution contains a server module that implements the memcached text protocol. This allows memcached clients to talk to one or several Infinispan backed memcached servers. These servers could either be working standalone just like memcached does where each server acts independently and does not communicate with the rest, or they could be clustered where servers replicate or distribute their contents to other Infinispan backed memcached servers, thus providing clients with failover capabilities.

Answer 2

It does make sense to do what you're suggesting. We've experienced the same issue with memcached in that the overhead to serialize objects back and forth isn't worth using it alone for a high volume application. Having a local cache reduces load on the application side while memcached reduces load on the database side. The downside comes with the additional complexity of writing two layers of caches and maintaining cache coherency. I'd try to minimize where you need to use it.