QoS Management l Many distributed applications have real- time requirements that coexist with tradition non-real-time applications. l Resources must be allocated and scheduled to ensure that the QoS requirements are met. The process of allocating and scheduling resources is called QoS Management. l Application QoS requirements are considered soft if the application is considered correct even if the QoS requirements are not met. l Two approaches to QoS Management:

QoS Management (cont) Static approach to QoS Management guarantees a resource allocation to an application by permanently allocating an amount of a resource for the lifetime of the application. This allocation is based on worst case need which is: difficult to estimate in a dynamic environment overestimating wastes limited resources Specification Negotiation Translation Admission Control Allocation and Scheduling

QoS Management (cont) Dynamic approach allocates and deallocates resource based on the application’s ability to meet its QoS requirements. must monitor the application through instrumentation to determine when a QoS requirement is not being met must determine the cause of the QoS requirement violation (QoS fault) must enforce the QoS requirement by adjusting resources within the managed environment Specification Negotiation Translation Admission Control Allocation and Scheduling Monitoring Violation Detection and Location EnforcementAdaptation

Policies l Policies exist to specify desired behavior of a system and actions to take upon satisfaction on a condition l By using policies to drive QoS management the user specifies what the system is to provide without having to specify how to do it l Allows the QoS requirements to be dynamic since the requirements may change for different applications, and instances of the same application l The Policy: “ The number of video frames displayed to the user must be 25 plus or minus 2 ” instructs the QoS Management system that the QoS requirement (fps) has a minimum threshold of 23 fps and a maximum threshold of 27 fps.

Instrumentation l Sensors collect and monitor data with probes inserted into original code l Actuators invoke actions on process l Coordinator serves as intermediary between management system and sensors/actuators l Thresholds specified in policies are monitored by sensors and reported to coordinator when violated l Policy violations are reported to management system by coordinator Original Process Coordinator actuator sensor

QoS Host Daemon l QoS Host Daemons apply policy violation reports from instrumented processes as facts in fact base l A CLIPS inference engine enforces policy violations by using the facts issued in violation reports by instrumented processes and known rules. l Each host contains a QoS Daemon for enforcing policy violations that have been caused by local resources or for other policy enforcement actions with local responses. (I.e disabling management) Inference Engine Rule Base Fact Base Communication CPU Manager Memory Manager Other Managers

QoS Domain Manager l Policy violations that requires non-local corrective actions are enforced through communication with a QoS Domain Manager Inference Engine Rule Base Fact Base Communication CPU Manager Memory Manager Other Managers Inference Engine Rule Base Fact Base Communication Host 1Host 2 Inference Engine Rule Base Fact Base Communication CPU Manager Memory Manager Other Managers

QoS Domain Manager (cont) l QoS Domain Manager can request data from instrumented processes on other hosts through the QoS Host Daemon that the process exists on. l QoS Domain Manager can modify resource allocations to a managed process through the process host’s QoS Host Daemon. l If a policy’s enforcement spans multiple domains the QoS Domain Manager can interact with other QoS Domain Managers.