Support for invalidation of FedX SourceSelectionCache and allow custom implementations

[aschwarte10]

Problem description

The current implementation of the FedX source selection relies on an in-memory guava cache. Via configuration it is possible already to configure the specification of the guava cache (e.g. to set expiration time)

What is currently missing is the possibility to invalidate the cache upon write operations to one of the federation members.

In addition, the implementation of the cache cannot be adjusted in extensions, as it is created in non-accessible code in org.eclipse.rdf4j.federated.FederationContext.createSourceSelectionCache(). Note that the cache itself is defined in an interface already.

Preferred solution

For the first part of the enhancement, it is desired to add invalidate methods to the org.eclipse.rdf4j.federated.cache.SourceSelectionCache interface

For the second part, it can be an option to define the source selection implementation using FedXConfig, maybe similar to the TaskWrapper.

Are you interested in contributing a solution yourself?

Yes

Alternatives you've considered

No response

Anything else?

No response