Scaling Policy Concepts

• Metrics– Periodically gather usage information about a

component e.g. queue length, response time, memory usage

• Alerts (Conditions)– Analyze numbers collected by one or more metrics to

reach a boolean conclusion

• Triggers (Action)– Invoked by alerts to scale up/down or take some other

action

Scaling Policy Concepts• Application Components have one or more

Metrics (we may need a management resource to house the metrics)

• Assembly has one or more Alerts (conditions) and one or more Triggers (actions)

• Each Alert uses values from one or more metrics• Each Alert can initiate one or more triggers• Triggers may act in several ways. They may scale

a component up or down by POSTing to a scaling URL on the component. Or they may send an email or a SMS message, etc.

Scaling Policy Relationships

Assembly

Application Component

Metric

Alert (Condition)

Contains

1

*

Trigger (Action)

Platform Component

11

1

1

*

*Initiates

Has

*

Has

*

Uses

1 *Has

11

**

Acts onActs on

- Send email- Send SMS- Scale by posting to URL

What Goes in the Spec?

• Provide hooks/skeletons for enable metrics, actions and triggers to be added

• No normative scaling resources• Perhaps add examples of scaling resources