Cache replication

 

Data is generated one time and copied or replicated to other servers in the cluster, thus saving execution time and resources. Caching in a cluster has additional concerns. In particular, the same data could be required, and hence, generated in multiple places. Also, the access the resources need to generate the cached data can be restricted, preventing access to the data.

Cache replication addresses these concerns by generating the data one time and copying or replicating it to the other servers in the cluster. It also aids in cache consistency, in that cache entries that are not needed are removed or replaced.

The configuration specific to replication of data can exist as part of the Web container dynamic cache configuration accessible through the administrative console, or on a per cache entry basis through the cachespec.xml file. This includes the option to configure cache replication at the Web container level, but disabling it for a specific cache entry.

Cache replication can take on three forms:

• PUSH - Send out new entries, both ID and data, and updates to those entries.

• PULL - Requests data from other servers in the cluster when that data is not locally present.

• PUSH/PULL - Sends out IDs for new entries, then, only request from other servers in the cluster entries for IDs previously broadcast. The dynamic cache always sends out cache entry invalidations.

The dynamic cache provides a batch update option. Specifically, for PUSH or PUSH/PULL, the dynamic cache broadcasts the update asynchronously, based on a timed interval rather than sending them immediately upon inception. Invalidators are sent immediately. Distribution of invalidations addresses the issue of stale data residing in a cluster.

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Configure cache replication