feat(autoscaling): add instanceMonitoring option

Gives users the option to choose between detailed and basic monitoring.
Defaults to detailed when not specified, maintaining current behavior.

fixes aws#8212

packages/@aws-cdk/aws-autoscaling/README.md

@@ -224,6 +224,11 @@ To enable the max instance lifetime support, specify `maxInstanceLifetime` prope
 for the `AutoscalingGroup` resource. The value must be between 7 and 365 days(inclusive).
 To clear a previously set value, just leave this property undefinied.
 
+### Instance Monitoring
+
+To disable detailed instance monitoring, specify `instanceMonitoring` property
+for the `AutoscalingGroup` resource as `Monitoring.BASIC`. Otherwise detailed monitoring
+will be enabled.
 
 
 ### Future work

packages/@aws-cdk/aws-autoscaling/lib/auto-scaling-group.ts

@@ -21,6 +21,21 @@ import { BlockDevice, BlockDeviceVolume, EbsDeviceVolumeType } from './volume';
  */
 const NAME_TAG: string = 'Name';
 
+/**
+ * The monitoring mode for instances launched in an autoscaling group
+ */
+export enum Monitoring {
+  /**
+   * Generates metrics every 5 minutes
+   */
+  BASIC,
+
+  /**
+   * Generates metrics every minute
+   */
+  DETAILED,
+}
+
 /**
  * Basic properties of an AutoScalingGroup, except the exact machines to run and where they should run
  *
@@ -199,6 +214,18 @@ export interface CommonAutoScalingGroupProps {
    * @default none
    */
   readonly maxInstanceLifetime?: Duration;
+
+  /**
+   * Controls whether instances in this group are launched with detailed or basic monitoring.
+   *
+   * When detailed monitoring is enabled, Amazon CloudWatch generates metrics every minute and your account
+   * is charged a fee. When you disable detailed monitoring, CloudWatch generates metrics every 5 minutes.
+   *
+   * @see https://docs.aws.amazon.com/autoscaling/latest/userguide/as-instance-monitoring.html#enable-as-instance-metrics
+   *
+   * @default Monitoring.DETAILED
+   */
+  readonly instanceMonitoring?: Monitoring;
 }
 
 /**
@@ -468,6 +495,7 @@ export class AutoScalingGroup extends AutoScalingGroupBase implements
       imageId: imageConfig.imageId,
       keyName: props.keyName,
       instanceType: props.instanceType.toString(),
+      instanceMonitoring: props.instanceMonitoring !== undefined ? (props.instanceMonitoring === Monitoring.DETAILED) : undefined
       securityGroups: securityGroupsToken,
       iamInstanceProfile: iamProfile.ref,
       userData: userDataToken,

packages/@aws-cdk/aws-autoscaling/test/test.auto-scaling-group.ts

@@ -830,6 +830,26 @@ export = {
     test.done();
   },
 
+  'can configure instance monitoring'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = mockVpc(stack);
+
+    // WHEN
+    new autoscaling.AutoScalingGroup(stack, 'MyStack', {
+      instanceType: ec2.InstanceType.of(ec2.InstanceClass.M4, ec2.InstanceSize.MICRO),
+      machineImage: new ec2.AmazonLinuxImage(),
+      vpc,
+      instanceMonitoring: autoscaling.Monitoring.BASIC,
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::AutoScaling::LaunchConfiguration', {
+      InstanceMonitoring: false,
+    }));
+    test.done();
+  },
+
   'throws if ephemeral volumeIndex < 0'(test: Test) {
     // GIVEN
     const stack = new cdk.Stack();