feat(autoscaling): health check configuration (#3390) (#3436)

Implements missing Auto Scaling Group properties [HealthCheckType](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-as-group.html#cfn-as-group-healthchecktype) and [HealthCheckGracePeriod](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-as-group.html#cfn-as-group-healthcheckgraceperiod)
They are grouped in a `healthCheck` object property.
The constructor checks that the following requirement is fulfilled:

> If you are adding an ELB health check, you must specify this property.


Fixes #3381

Author: RomainMuller

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

@@ -156,6 +156,13 @@ export interface CommonAutoScalingGroupProps {
    * @default none
    */
   readonly spotPrice?: string;
+
+  /**
+   * Configuration for health checks
+   *
+   * @default - HealthCheck.ec2 with no grace period
+   */
+  readonly healthCheck?: HealthCheck;
 }
 
 /**
@@ -444,7 +451,9 @@ export class AutoScalingGroup extends AutoScalingGroupBase implements
           ],
         }
       ],
-      vpcZoneIdentifier: subnetIds
+      vpcZoneIdentifier: subnetIds,
+      healthCheckType: props.healthCheck && props.healthCheck.type,
+      healthCheckGracePeriod: props.healthCheck && props.healthCheck.gracePeriod && props.healthCheck.gracePeriod.toSeconds(),
     };
 
     if (!hasPublic && props.associatePublicIpAddress) {
@@ -673,6 +682,61 @@ export enum ScalingProcess {
   ADD_TO_LOAD_BALANCER = 'AddToLoadBalancer'
 }
 
+/**
+ * EC2 Heath check options
+ */
+export interface Ec2HealthCheckOptions {
+  /**
+   * Specified the time Auto Scaling waits before checking the health status of an EC2 instance that has come into service
+   *
+   * @default Duration.seconds(0)
+   */
+  readonly grace?: Duration;
+}
+
+/**
+ * ELB Heath check options
+ */
+export interface ElbHealthCheckOptions {
+  /**
+   * Specified the time Auto Scaling waits before checking the health status of an EC2 instance that has come into service
+   *
+   * This option is required for ELB health checks.
+   */
+  readonly grace: Duration;
+}
+
+/**
+ * Health check settings
+ */
+export class HealthCheck {
+  /**
+   * Use EC2 for health checks
+   *
+   * @param options EC2 health check options
+   */
+  public static ec2(options: Ec2HealthCheckOptions = {}): HealthCheck {
+    return new HealthCheck(HealthCheckType.EC2, options.grace);
+  }
+
+  /**
+   * Use ELB for health checks.
+   * It considers the instance unhealthy if it fails either the EC2 status checks or the load balancer health checks.
+   *
+   * @param options ELB health check options
+   */
+  public static elb(options: ElbHealthCheckOptions): HealthCheck {
+    return new HealthCheck(HealthCheckType.ELB, options.grace);
+  }
+
+  private constructor(public readonly type: string, public readonly gracePeriod?: Duration) { }
+}
+
+enum HealthCheckType {
+  EC2 = 'EC2',
+  ELB = 'ELB',
+}
+
 /**
  * Render the rolling update configuration into the appropriate object
  */

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

@@ -397,6 +397,49 @@ export = {
     test.done();
   },
 
+  'can configure EC2 health check'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack(undefined, 'MyStack', { env: { region: 'us-east-1', account: '1234' } });
+    const vpc = mockVpc(stack);
+
+    // WHEN
+    new autoscaling.AutoScalingGroup(stack, 'MyFleet', {
+      instanceType: ec2.InstanceType.of(ec2.InstanceClass.M4, ec2.InstanceSize.MICRO),
+      machineImage: new ec2.AmazonLinuxImage(),
+      vpc,
+      healthCheck: autoscaling.HealthCheck.ec2()
+    });
+
+    // THEN
+    expect(stack).to(haveResourceLike("AWS::AutoScaling::AutoScalingGroup", {
+      HealthCheckType: 'EC2',
+    }));
+
+    test.done();
+  },
+
+  'can configure EBS health check'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack(undefined, 'MyStack', { env: { region: 'us-east-1', account: '1234' } });
+    const vpc = mockVpc(stack);
+
+    // WHEN
+    new autoscaling.AutoScalingGroup(stack, 'MyFleet', {
+      instanceType: ec2.InstanceType.of(ec2.InstanceClass.M4, ec2.InstanceSize.MICRO),
+      machineImage: new ec2.AmazonLinuxImage(),
+      vpc,
+      healthCheck: autoscaling.HealthCheck.elb({grace: cdk.Duration.minutes(15)})
+    });
+
+    // THEN
+    expect(stack).to(haveResourceLike("AWS::AutoScaling::AutoScalingGroup", {
+      HealthCheckType: 'ELB',
+      HealthCheckGracePeriod: 900
+    }));
+
+    test.done();
+  },
+
   'can add Security Group to Fleet'(test: Test) {
     // GIVEN
     const stack = new cdk.Stack(undefined, 'MyStack', { env: { region: 'us-east-1', account: '1234' } });