IS-Client

The IS-Client is an interface defined in the context of the gCore Framework to decouple gCube Services from the specific implementation of the Information Service. In conjunction with the IS-Publisher it represents the mediation layer gCube Services will rely on to interact with the Information Service as a whole. Such interfaces implement respectively the production/publishing (IS-Publisher) and the consumption/query (IS-Client).

Functions

The main functions supported from the IS-Client are:

• getQuery() – which takes as input parameter a message characterising the interface implementation to be used and instructing the framework to use it (by relying on the dynamic class loader mechanism);
• execute() – which takes as input parameter a message containing a query, a query scope and a context the requestor is operating in and returns the list of Information Service entries matching the query and the rest of constraints.

In addition to such functions the interface predefines the list of query typologies (a.k.a. templates) that must be implemented. Three classes of queries are envisaged:

• gCube Resources query, i.e. a query template to identify gCube Resources by imposing constraints on their profiles. For each existing gCube Resource a query template of this type exists, e.g. there is a GCUBERIQuery for issuing queries on Running Instance Resources, GCUBEGHNQuery for issuing queries on gHN Resources;
• WS-Resource query, i.e. a query template to identify properties exposed through WS-ResourceProperty;
• generic query, i.e. a query template to execute custom queries on the entries stored in the Information Service.

The ExistLibrary is the implementation of such a Library equipping the gCore Framework.