Chapter 24. Set Up the L1 Cache

24.1. About the L1 Cache

The Level 1 (or L1) cache stores remote cache entries after they are initially accessed, preventing unnecessary remote fetch operations for each subsequent use of the same entries. The L1 cache is only available when Red Hat JBoss Data Grid's cache mode is set to distribution. In other cache modes any configuration related to the L1 cache is ignored.
When caches are configured with distributed mode, the entries are evenly distributed between all clustered caches. Each entry is copied to a desired number of owners, which can be less than the total number of caches. As a result, the system's scalability is improved but also means that some entries are not available on all nodes and must be fetched from their owner node. In this situation, configure the Cache component to use the L1 Cache to temporarily store entries that it does not own to prevent repeated fetching for subsequent uses.
Each time a key is updated an invalidation message is generated. This message is multicast to each node that contains data that corresponds to current L1 cache entries. The invalidation message ensures that each of these nodes marks the relevant entry as invalidated. Also, when the location of an entry changes in the cluster, the corresponding L1 cache entry is invalidated to prevent outdated cache entries.