1.2.4. Thread safety

The cache is completely thread-safe. It employs multi-versioned concurrency control (MVCC) to ensure thread safety between readers and writers, while maintaining a high degree of concurrency. The specific MVCC implementation used in JBoss Cache allows for reader threads to be completely free of locks and synchronized blocks, ensuring a very high degree of performance for read-heavy applications. It also uses custom, highly performant lock implementations that employ modern compare-and-swap techniques for writer threads, which are tuned to multi-core CPU architectures.

Multi-versioned concurrency control (MVCC) is the default locking scheme since JBoss Cache 3.x. Optimistic and pessimistic locking schemes from older versions of JBoss Cache are still available but are deprecated in favor of MVCC, and will be removed in future releases. Use of these deprecated locking schemes are strongly discouraged.

The JBoss Cache MVCC implementation only supports READ_COMMITTED and REPEATABLE_READ isolation levels, corresponding to their database equivalents. See the section on Chapter 11, Transactions and Concurrency for details on MVCC.