分布式环境中的JPA PersistenceContext

Question

Based on my understanding, transactions are not flushed immediately once they are completed. They sit in a cache in memory and only get written to the DB when the EntityManager determines that it is cost effective to do so. I believe the L1 cache is utilized in this case, but correct me if I'm wrong.

My question is, in a distributed environment, is the cache used by the Persistence Context distributed?

Answer 1

L1 cache (session cache, persistence context) always works the same way, no matter wheteher your environment is distributed or not. Session cache belongs to a session, and you can have multiple sessions, either on the same machine or on different machines, so that it doesn't matter.

In distributed environment you need to care about the second level cache, if you use it.

If you run your application in a cluster, you need to use cluster-capable L2 cache implementation, if you JPA provider supports it (see, for example, 21.2. The Second Level Cache from Hibernate documentation).

If you have other applications accessing the same database, you need to carefully configure caching strategies to avoid inconsistency in critical cases and tolerate possible inconsistency in other cases.