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Chapter 4. The Persistence SPI
In Red Hat JBoss Data Grid, persistence can configure external (persistent) storage engines. These storage engines complement JBoss Data Grid's default in-memory storage.
Persistent external storage provides several benefits:
- Memory is volatile and a cache store can increase the life span of the information in the cache, which results in improved durability.
- Using persistent external stores as a caching layer between an application and a custom storage engine provides improved Write-Through functionality.
- Using a combination of eviction and passivation, only the frequently required information is stored in-memory and other data is stored in the external storage.
4.1. Persistence SPI Benefits
The Red Hat JBoss Data Grid implementation of the Persistence SPI offers the following benefits:
- Alignment with JSR-107 (http://jcp.org/en/jsr/detail?id=107). JBoss Data Grid's
CacheWriterandCacheLoaderinterfaces are similar to the JSR-107 writer and reader. As a result, alignment with JSR-107 provides improved portability for stores across JCache-compliant vendors. - Simplified transaction integration. JBoss Data Grid handles locking automatically and so implementations do not have to coordinate concurrent access to the store. Depending on the locking mode, concurrent writes on the same key may not occur. However, implementors expect operations on the store to originate from multiple threads and add the implementation code accordingly.
- Reduced serialization, resulting in reduced CPU usage. The new SPI exposes stored entries in a serialized format. If an entry is fetched from persistent storage to be sent remotely, it does not need to be serialized (when reading from the store) and then serialized again (when writing to the wire). Instead, the entry is written to the wire in the serialized format as fetched from the storage.
