Part 2, Chapter 16
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Table of content
This chapter explains how enterprise caching works, from database internal buffers, to application-level caching, and the second-level cache offered by Hibernate.
16. Caching 16.1 Caching flavors 16.2 Cache synchronization strategies 16.2.1 Cache-aside 16.2.2 Read-through 16.2.3 Write-invalidate 16.2.4 Write-through 16.2.5 Write-behind 16.3 Database caching 16.4 Application-level caching 16.4.1 Entity aggregates 16.4.2 Distributed key/value stores 16.4.3 Cache synchronization patterns 16.4.4 Synchronous updates 16.4.5 Asynchronous updates 18.104.22.168 Change data capture 16.5 Second-level caching 16.5.1 Enabling the second-level cache 16.5.2 Entity cache loading flow 16.5.3 Entity cache entry 22.214.171.124 Entity reference cache store 16.5.4 Collection cache entry 16.5.5 Query cache entry 16.5.6 Cache concurrency strategies 126.96.36.199 READ_ONLY 188.8.131.52.1 Inserting READ_ONLY cache entries 184.108.40.206.2 Updating READ_ONLY cache entries 220.127.116.11.3 Deleting READ_ONLY cache entries 18.104.22.168 NONSTRICT_READ_WRITE 22.214.171.124.1 Inserting NONSTRICT_READ_WRITE cache entries 126.96.36.199.2 Updating NONSTRICT_READ_WRITE cache entries 188.8.131.52.3 Risk of inconsistencies 184.108.40.206.4 Deleting NONSTRICT_READ_WRITE cache entries 220.127.116.11 READ_WRITE 18.104.22.168.1 Inserting READ_WRITE cache entries 22.214.171.124.2 Updating READ_WRITE cache entries 126.96.36.199.3 Deleting READ_WRITE cache entries 188.8.131.52.4 Soft locking concurrency control 184.108.40.206 TRANSACTIONAL 220.127.116.11.1 XA_Strict mode 18.104.22.168.2 XA mode 22.214.171.124.3 Inserting TRANSACTIONAL cache entries 126.96.36.199.4 Updating TRANSACTIONAL cache entries 188.8.131.52.5 Deleting TRANSACTIONAL cache entries 16.5.7 Query cache strategy 184.108.40.206 Table space query invalidation 220.127.116.11 Native SQL statement query invalidation
Caching is everywhere, and enterprise systems are no different. Before jumping to an application-level cache, it’s important to know that most database systems are designed to make use of caching, as mush as possible. Some database systems come with their own shared buffers, whereas others rely on the underlying operating system for caching disk pages in memory.
Even after tuning the database, to overcome the networking overhead, and to level-up traffic spikes, it’s common to use an application-level cache, like Redis or Memcached.
These key-value stores can be distributed on several nodes, therefore providing increased availability and data sharding capabilities. One major advantage of storing entity aggregates in a key-value database is that the application can work in a read-only mode even when the entire database cluster is down, for maintenance.
The only downside for using an application-level cache is to ensure that the two separate sources of data do not drift apart. For this reason, there are several cache concurrency strategies: cache-aside, read-through, write-through.
Being tightly coupled with Hibernate, thee second-level cache can speed up reads, without compromising data consistency. However, choosing the right cache concurrency strategy (READ_ONLY, NONSTRICT_READ_WRITE, READ_WRITE, TRANSACTION) requires understanding the inner-workings of the cache update policy. The entity query cache has its own rules, and because it employs an aggresive cache invalidation policy, it only applies to a certain data access pattern criteria.
With almost 60 pages, the Caching chapter is one of the largest chapters of this book, so enjoy reading High-Performance Java Persistence!