trinity 3.3 spec

Table of Contents Trinity Use Case Service Implications Autoscaling CloudWatch ELB Service Interactions

Trinity Use Case

Briefly, the use case is:

1. A horizontally scalable app whose instances are managed as an autoscaling group (ASG)
2. The ASG registers its instances w/ an ELB
3. The ELB produces metrics that are available through CloudWatch
4. The ELB metrics are used to compute a custom metric which factors in other values, too.
5. The custom metric is put back into CloudWatch
6. The custom metric is used to drive a CloudWatch alarm
7. The CloudWatch alarm action triggers the execution of the ASG's scaling policy.

Service Implications

• See Autoscaling 3.3
• See ELB 3.3
• See CloudWatch 3.3

Autoscaling

• Define an Autoscaling group
• ASG definition identifies related load balancer
• ASG can use ELB health check type
• ASG scaling policies invokable through ExecutePolicy

CloudWatch

• PutMetricData can be used to submit custom metric
• GetMetricStatistics can be used on system and custom metrics
• Alarms can be defined
• Alarm actions are working

ELB

• Registering instances is possible
• Gathers AWS defined metrics for load balancers

Service Interactions

• Autoscaling -> ELB: ASG registers member instances with ELB
• ELB -> CW: AWS defined system metrics are submitted to CW
• User -> CW: Can compute statistics on system metrics
• User -> CW: Can submit custom metrics
• CW -> Autoscaling: CW alarm action triggers scaling policy execution for autoscaling group

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tag:rls-3.3 tag:trinity tag:autoscaling tag:cloudwatch tag:elb