Our initial architectural designs assume that applications will be constructed by composing services, each of which has some common properties and behaviours. When executing applications, we can assume that certain core “infrastructure” services or properties are available in the environment of the application. In the context of NextGRID we are building on the HTTP(S), SOAP, WSDL1.1, WS-Addressing, WS-Security, SAML1.1 and X.509 protocols and the OGSA WSRF Basic Profile 1.0 and SLA Template interfaces. A key architectural requirement is that service composition should result in self-similar structures that are themselves amenable to NextGRID composition rules.
A key aspect of the current NextGRID conceptual architecture is that all interactions will be governed through bipartite “partnership” SLAs. NextGRID believes that SLAs should be used to build relationships between service providers and consumers, and provide the necessary information to set up the environment and components to manage the service. The SLA should outline details that are agreed by both parties, and allow for the service to be operated and monitored in accordance with the consumer requirements and in an economically sustainable manner.
Neither the service provider nor the consumer will gain a significant advantage by violating an SLA. The customer will not get the service they require, and the provider’s reputation will be damaged –perhaps to the stage where the customer will not use the service again. It is therefore proposed to have a framework that is less focused on monitoring of every element of every transaction and see the relationship between provider and consumer as a partnership within a context – with that context being provided by the SLA. Where necessary, monitoring and enforcement are provided for, but the aim of the SLA idea is to focus on the partnership and agreement side rather than the violation side of the contract.
The benefit of such a proposal is that the NextGRID architecture can support both community minded approaches as well as the commercial offering of services. SLAs allow for services to be provided in exchange for an equivalent set of services or a cash purchase. In a commercial context where services are provided for a fee, and the fact the service is provided on a Grid infrastructure is irrelevant to the end user, it is more important to provide specific QoS levels that need to be communicated, agreed upon and upheld.
Approaching the issue of SLAs in this partnership model allows for a lighter-weight monitoring infrastructure and avoids having a monitoring system that is more expensive to provide in economic, computational or time terms than some of the services it is tasked with monitoring.
We believe that an SLA is a key component to be considered at all stages in the lifecycle of a service. The policies for managing the service, the probes for monitoring it and the acceptable quality of service terms to offer to a consumer should be produced at the same time as the service is designed and developed. This ensures the correct information is available to be able to guarantee the QoS levels necessary that a consumer will consider entering into an agreement with a provider to use the service.
Having completed the initial architectural design work with regard to SLAs, the Grid foundations activity is now producing a prototype implementation of an SLA template interface. Other tasks are analysing how “collective” inter-enterprise computing business issues can be addressed through pairwise SLAs between participants, by studying how accountability and billing can be represented in SLA terms, for example. These ideas will then be implemented, so that NextGRID industrial partners can experiment with using this technology for real world applications, to prove its efficacy or, alternatively, show where we have gone wrong in our design and thinking. It is through the many strands of work within NextGRID such as this that we are building the next generation of Grid that will meet the needs of business and commerce.
Gartner Group–the well known IT analysis company–have widely publicised the idea of a “hype cycle for emerging technologies” In the Gartner Hype Cycle Special Report for 2005, Grid Computing finds itself halfway down the slope from the “peak of inflated expectations” to the “trough of disillusionment.” Interestingly however, Gartner indicates that they expect it to reach the “plateau of productivity” within 2-5 years.
Achieving our goal of productive Grid computing for business and science requires that we focus both on incremental improvements of current technologies and also that we are prepared to think beyond the status quo and try out new ideas. This is a key premise of the NextGRID project.
