Prerequisites:
- ECS Copilot: ECS Copilot that has been overridden to expose CDK. See svc override — AWS Copilot CLI. Probably could use the same principles with regular CDK as well but this particular example assumes we are using ECS Copilot.
- Typescript
- CDK v2
- NPM
- CDK IAM Floyd (Library for helping manage AWS IAM)
npm install cdk-iam-floyd
- tranformService(): This is the function that starts of with
const service = this.template.getResource("Service") as ecs.CfnService;
Notes:
As mentioned before, this could be used for any CDK project. However, for this demonstration ECS Copilot is assumed which will include some commands that simply would not be necessary.
Lets get started:
transformService() {
let minCapacity = 2;
let maxCapacity = 48;
let queueName = "your_queue_name"
## With regular CDK, you will have the Service Object directly.
const service = this.template.getResource("Service") as ecs.CfnService;
const clusterName = service.cluster;
const serviceName = service.attrName;
const scalingRole = new iam.Role(this, 'ServiceScalingRole', {
assumedBy: new iam.ServicePrincipal('ecs.application-autoscaling.amazonaws.com'),
inlinePolicies: {
'ScalingRoleInlinePolicy': new PolicyDocument({
statements: [
new floyd.ApplicationAutoscaling().allow().onAllResources().allActions(),
new floyd.Ecs().allow().onAllResources()
.toDescribeServices()
.toUpdateService(),
new floyd.Cloudwatch().allow().onAllResources()
.toDescribeAlarms()
.toPutMetricAlarm()
.toDeleteAlarms()
.toDescribeAlarmHistory()
.toDescribeAlarmsForMetric()
.toGetMetricStatistics()
.toListMetrics()
.toDisableAlarmActions()
.toEnableAlarmActions(),
new floyd.Iam().allow().onAllResources()
.toCreateServiceLinkedRole(),
new floyd.Sns().allow().onAllResources()
.toCreateTopic()
.toSubscribe(),
new floyd.Sns({
actions: [
"sns:Get*",
"sns:List*"
]
}).allow().onAllResources()
]
})
}
});
// First, get the ScalableTarget associated with the service
const resourceId = `service/${clusterName}/${serviceName}`;
const scalableTarget = new appscaling.CfnScalableTarget(this, 'ServiceScalableTarget', {
maxCapacity: maxCapacity,
minCapacity: minCapacity,
resourceId: resourceId,
roleArn: scalingRole.roleArn,
scalableDimension: 'ecs:service:DesiredCount',
serviceNamespace: 'ecs',
});
// This and the previous are only necessary because of ECS Copilot.
// Could just declare the ScalableTarget directly with CDK.
const cdkScalableTarget = appscaling.ScalableTarget.fromScalableTargetId(
this,
'CdkServiceScalableTarget',
scalableTarget.ref,
)
const metric = new cloudwatch.Metric({
namespace: 'AWS/SQS',
metricName: 'ApproximateNumberOfMessagesVisible',
dimensionsMap: {
QueueName: queueName,
},
statistic: 'Average',
});
}
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