Design of a Model-Based SLA Management Service and Its Applications over Distributed SOA Environments - Grid Computing: Infrastructure, Service, and Applications - page 253

provider may describe the creation constraints in the SLA templates to
dei ne the terms and conditions that a valid proposal should conform to.
Once an SLA proposal has been submitted, SLA Manager will check
whether it is a valid proposal. An SLA will be created only if the proposal
conforms to the creation constraints and is agreed upon by both parties.

10.3.1.2.3
The purpose of SLA monitoring and archiving is to automatically mea-
sure and monitor the status of the SLAs during both SLA negotiation and
service delivery stages. The status of an SLA may vary during the lifecycle
of an SLA. For example, an SLA can be in “active,” “expired,” or “canceled”
state, or even in “changed” or “violated” state. Operation getState() checks
the SLA status. Each SLA status may be associated with a time stamp or
certain conditions that are specii ed in the SLAs. Therefore, it requires
efi cient mechanisms to automatically monitor the status of SLA, main-
tain the different versions of SLAs, and notify the relevant parties when
changes happen. Sometimes, SLA monitoring mechanisms are required
to check the status of a job execution, predict the performance, and inform
the service manger to adjust the resource allocation at runtime so as to
prevent SLA violation or service suspension.

Monitoring and archiving

10.3.1.2.4
An SLA violation may happen when some of the agreed terms in an SLA are
violated or the terms cannot be successfully fuli lled by the service execution
environment. Adaptation mechanisms are required to react to the violations
and trigger the actions of automatic adaptation and adjustment. For example,
it is hard to accurately predict the performance for many of the high-
performance computing applications just by looking at the input parameters.
In such cases, the SLA needs to be established based on prior estimation
regarding resource requirements and time to completion. Therefore, efi cient
adaptation mechanisms are crucial to handling the uncertainties in perfor-
mance and resource availabilities in dynamic environments.
In real-life situations, not all the SLA-relevant operations are required for
every service provider. Therefore, we propose an SLA manager that is
based on a generic core model with pluggable modules/components so as
to allow the service providers to customize their implementations. Figure
10.2 shows the components of SLA Manager with the SLA-based service as
its core to support various SLA-related operations. The functionalities of
each group are governed by a pluggable component that connects to the
SLA-based service.

Violation and adaptation

10.3.1.3 Service Model Creation over the Shared Services Platform

Figure 10.3 demonstrates the process of creating a service model for SLA
management over the shared service platform. To instantiate a service