Common Libraries Specification

A rich set of software libraries supports key management functions over software and hardware resources, as well the development of software resources that integrate or interface the system.

This document overviews the range of software libraries that are available within the system as part its core facilities.

Overview

Core facilities such as publication and lifetime management of software and hardware resources are in part implemented locally to the resources, via software libraries that interact with remote services on behalf of the resources.

Software libraries provide also tooling that simplifies and homogenises the development of components that are part of the system, extend the system, or interface the system.

Key features

Collectively, the core libraries provide for:

publication, lifetime management, and monitoring for software and hardware resources

configuration-driven synthesis and publication of resource descriptions;

detection of, publication of, and transition to key states in resource lifetime;

transparent scope management for hardware and software resources

assignment, removal, and validation of scope for hardware resources, service endpoints, and service instances;

scope validation for incoming calls;

proxy mechanisms for scoping of outgoing calls;

transparent security management for hardware and software resources

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fault management support for software resource development

automatic assignment and handling of unrecoverable, retry-same, and retry-equivalent failure semantics;

state management support for software resource development

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

resource publication and discovery support for software resource development

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

resource encryption and decryption for publication and querying;

remote interaction support for software resource development

high-level model of service calls

best-effort strategies for service replica discovery and replica management;

caching;

plugin management support for software resource development

transparent plugin discovery, registration, unregistration;

Design

Philosophy

The system delivers its library support for resource management and software resource development in two distinct forms.

In the first form, it provides a single a single application framework (the gCube Application Framework) which is tightly integrated with a particular set of runtime technologies (Globus’ WS-Core Container). Framework and runtime are bundled in a single distribution (gCore) which can be installed on hardware resources to bring them under the management regime of the system. The framework includes a set of programming abstractions that simplify significantly the development of software resources which can again be brought under the management regime of the system.

In the second form, the system provides a set of libraries that specialise in different management and development support functions. The libraries that support resource management functions are independent of runtime technologies and raise no compile-time or run-time dependencies on the managed resources. The libraries that support development of software resources do so in a modular fashion, which allows partial and on-demand dependencies on system facilities.

The transparencies granted by the first approach 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 of the second approach aligns with modern practices and brings a wider range of resources under the management regime of the system.

Architecture

The core facilities of the system rely on the following libraries:

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

• ghn-service: a system component that transparently manages HTTP services that run in a Servlet container;

• ghn-client: an extensible framework for system components that transparently manage clients of HTTP services;

• ghn-client-proxy: a system component that transparently manages client calls to HTTP services;

• common-clients: an API for client library development;

• common-gcore-clients: an extension of the common-clients API for clients of gCore services;

• common-scope: scope handling facilities;

• common-resources: an implementation of the resource model;

• common-resources-publish: local API of remote publication services;

• common-resources-query: local API of remote discovery services;

• common-resources-encryption: resource encryption/decryption facilities;

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.