Database Reference
In-Depth Information
Other
interface
invocation
Event
generation
Actuator
invocation
Element Manager
Functional Port
Computational
Element
Control Port
Element Manager
Element Manager
Element Manager
Operational Port
Autonomic Element
Internal
state
Rules
Contextual
state
Figure 5.5
An autonomic service in Accord.
An autonomic service extends a Grid service (such as the in-transit services
described above) with a control port, as shown in Figure 5.5. The control
augments the functional and operational ports that typically define computa-
tional elements, and supports external monitoring and steering. An autonomic
service also encapsulates a service manager, shown in Figure 5.5 on the right,
which monitors and controls the runtime behaviors of the managed service
according to changing requirements and state of applications as well as their
execution environment based on user-defined rules. As shown in the figure, the
manager uses the local state of the element as well as its context along with
user-defined rules to generate adaptations as well as management events. The
control port (Figure 5.5, left) consists of sensors that enable the state of the
service to be queried, and actuators that enable the behaviors of the service
to be modified. Rules are simple if-condition-then-action statements described
using XML and include service adaptation and service interaction rules. Ac-
cord is part of Project AutoMate,
32
which provides the required middleware
services.
The element (service) managers within the Accord programming system are
augmented with online controllers
33
,
34
as shown in Figure 5.6. The figure shows
LLC Controller
Optimization
Function
Self-Managing Element
LLC Controller
Computational
element model
Advice
Element Manager
Element Manager
Computational
Element
Contextual
state
Internal
state
Figure 5.6
Self-management using model-based control in Accord.
