Common Libraries Specification

The core facilities of the e-Infrastructure include a set of Java libraries that compose into solutions for managing the software and hardware of the e-Infrastructure, as well as for interacting with those resources. This document overviews such common libraries.

Overview

Common libraries are grouped in three main distributions:

• the Featherweight Stack (FWS) is the client stack of the e-Infrastructure, i.e. the set of libraries that allow clients to interact with its services, first and foremost the services of its enabling technologies;

• Smartgears is a set of libraries that transform services and service containers into resources of the e-Infrastructure. SmartGears meets, among others, the description, publication, lifecycle management, and controlled sharing requirements which characterise hardware and software managed by the e-Infrastructure;

• the gCube Application Framework (gCF) is a comprehensive framework to develop services for the e-Infrastructure, i.e. software written to run and be managed in it.

Key features

Collectively, the common libraries support the following management functions:

publication and discovery

periodic and event-based publication of resource profiles from initial configurations, both for hardware and software;

high-level models of resources, resource queries and query results;

best-effort discovery strategies with caching and fault tolerance;

resource encryption and decryption for publication and querying;

lifecycle management

state tracking, event-based state transitions, and remotely controlled state transitions, both for hardware and software;

controlled sharing

resource allocation to distinguished groups of users in alignment with dynamic policies, both for hardware and software resources;

policy enforcement at deployment time (for hardware) and at call time (for software);

policy propagation in outgoing calls;

security management

authentication and authorisation of calls to software resources.

development support for stateful services

WSRF-compliant support for access, persistence, publication, and discovery of service instances;

plugin management

plugin discovery, registration, unregistration for software resources;

Design

Philosophy

The available common libraries reflect two different design orientations:

• gCF is a conventional development framework that trades off development simplicity for development for flexibility. It is a library that sits at centre of software design and at the top of the software stack, providing solutions in the context of a well-defined set of technologies and in the assumption of deployment to a specific service container. The tradeoff is most advantageous for the services of the enabling technology, as it offers maximum integration between software and e-Infrastructure. Indeed, the framework is the basis upon which the vast majority of the service of the e-Infrastructure are built.

• SmartGears is instead designed as a "resource enabler" for existing software and service containers, where development and deployment cannot and should not be constrained. SmartGears delivers its management functions in a standard manner, i.e relying only on Servlet specifications, and transparently, i.e. without demanding source-level dependencies from applications. Overall, SmartGears can bring a wide range of software under the management regime of the e-Infrastructure, without requiring dedicated development. At the same time, it allows new services of the enabling technology to evolve along standard pathways, embracing technologies other than those mandated by gCF.

• Like SmartGears, the FWS is independent from technologies used by service implementations. The featherweight nature of the stack is in the footprint of its components, which is very small in terms of code, dependencies, and overall usage requirements. Overall, the FWS simplifies the task of clients that wish to interact with any services managed by the e-Infrastructure, gCF-based or SmartGears-based, thereby encouraging uptake.

Overall, the simplifications allowed by gCF have been instrumental to the rapid and consistent growth of the system, reducing significantly administration and development costs for hardware and software resources explicitly allocated to the system or developed for it. The commitment to lightweight integration mechanisms and design modularity in SmartGears and the FWS aligns with modern practices and brings a wider range of resources under the management regime of the e-Infrastructure.

Architecture

The main common libraries are the following:

• gcf: the gCube Application Framework, a one-stop solution for resource management support and software resource development support;

• common-smartgears: transparent management support for Servlet-based containers, applications, and services;

• common-scope: scope handling facilities for policy management;

• common-validator: annotation-based object validation facilities;

• common-utils-encryption: encryption and decryption support;

• common-gcore-resources: object binding of the resource model;

• common-events: annotation-based eventing support;

• common-gcore-stubs:client support for JAXWS-based proxies of remote gCF-based services;

• common-gcube-calls: base layer support for outgoing calls to any infrastructural service;

• common-jaxws-calls: JAX-WS binding of common-gcube-calls;

• discovery-client: generic API to formulate and submit queries for resource descriptions.

• ic-client: extends discovery-client to target the Information Collector service;

• registry-publisher: support to publish resource description with the Registry service;

• common-clients: base layer for high leve client libraries to any infrastructural service;

• common-featherweight-clients: extends common-clients for clients of standard gCF-based services;

• common-gcube-clients: extends common-clients for clients of SmartGears-enabled services;

Deployment

Common Libraries are a set of facilities available as Java libraries. Therefore, there is no deployment scheme for them. They are just individually and independently co-deployed with components that need to use a particular feature that one of the offers.