JBoss has released JBoss Cache 1.4 final, their distributed caching product which also includes PojoCache (formerly TreeCacheAOP). The release adds Buddy Replication and Data Gravitation features and also optimizes their RPC marshalling algorithm resulting in 20-50% improved performance and throughpout. JBoss Cache is the technology behind JBoss Application Server's HTTP and EJB session replication. InfoQ spoke to project leads Ben Wang and Manik Surtani to get more information.Previously, JBoss Cache multicasted cache changes across all nodes in the cluster, which would make it inefficient for cases where cache data is partitioned (such as when you have session affinity). With the new buddy replication feature, instead each server instance picks one or more 'buddies' in the cluster, and only replicates to these specific buddies. When asked about why one needs distributed caching if you have a cluster with session affinity, responded:
when you have a local cache+session affinity, you'd still want some replication for failover/high availability, one example being HTTP sessions. This is where buddy replication comes in, improving efficiency so you don't end up replicating your entire state across the cluster - just to nominated backup nodes.Buddy Replication is an important feature for the project to gain in order for it to become suitable for larger deployments where inter-node communications overhead must be minimized. Other commercial solutions such as Tangosol or IBM's ObjectGrid have had this for some time. Terracotta doesn't use/need a buddy system since data is replicated to a central cache server.
JBoss Cache uses JGroups, a group communication toolkit, to manage network-level communications between instances. Manik Surtani told InfoQ:
we've used this to build an RPC layer, wich we then use to replicate data across a cluster. Using JGroups, we get a number of things for free, including group membership and organisation, guaranteed message delivery, and network stack tuning (switching between TCP and UDP, tunnelling through firewalls if necessary, etc).PojoCache is a componeont of JBoss Cache which allows you to avoid interacting with the cache with a Map interface after update operations; instead, an object instance is added to the Cache with one initial PUT, and field-level changes to the object are intercepted transparently with aspects and then distributed across the cluster.
Ben Wang positioned JBoss Cache as a competitor to Tangosol (from the perspective of both being distributed Maps) and PojoCache as as more like Terracotta (from the AOP-driven, API-less perspective).