14.4. Locking Operations

The LockManager component is responsible for locking an entry before a write process initiates. The LockManager uses a LockContainer to locate, hold and create locks. There are two types of LockContainers JBoss Data Grid uses internally and their choice is dependent on the useLockStriping setting. The first type offers support for lock striping while the second type supports one lock per entry.

Red Hat JBoss Data Grid acquires remote locks lazily by default. The node running a transaction locally acquires the lock while other cluster nodes attempt to lock cache keys that are involved in a two phase prepare/commit phase. JBoss Data Grid can lock cache keys in a pessimistic manner either explicitly or implicitly.

Concurrency refers to the number of threads simultaneously interacting with the data grid. In Red Hat JBoss Data Grid, concurrency levels refer to the number of concurrent threads used within a lock container.

In JBoss Data Grid, concurrency levels determine the size of each striped lock container. Additionally, concurrency levels tune all related JDK ConcurrentHashMap based collections, such as those internal to DataContainers.