2.2. Indexing Modes

In Red Hat JBoss Data Grid's Query Module there are two options for storing indexes:

When the indexes are stored locally, each write to cache must be forwarded to all other nodes so that they can update their indexes. If the index is shared, only the node where the write originates is required to update the shared index.

Lucene provides an abstraction of the directory structure called directory provider, which is used to store the index. The index can be stored, for example, as in-memory, on filesystem, or in distributed cache.

In local mode, any Lucene Directory implementation may be used. The indexLocalOnly option is meaningless in local mode.

In replication mode, each node can store its own local copy of the index. To store indexes locally on each node, set indexLocalOnly to false, so that each node will apply the required updates it receives from other nodes in addition to the updates started locally.

Any Directory implementation can be used. When a new node is started it must receive an up to date copy of the index. Usually this can be done via resync, however being an external operation, this may result in a slightly out of sync index, particularly where updates are frequent.

Alternatively, if a shared storage for indexes is used (see Section 2.3.3, “Infinispan Directory Provider”), indexLocalOnly must be set to true so that each node will only apply the changes originated locally. While there is no risk of having an out of sync index, this causes contention on the node used for updating the index.

The following diagram demonstrates a replicated deployment where each node has a local index.

In both Distribution modes, the shared index must be used, with the indexLocalOnly set to true.

The following diagram shows a deployment with a shared index.

Indexing and searching of elements in Invalidation mode is not supported.