fix(autoscaling): Allow adding AutoScalingGroup to multiple target gr…

…oups (aws#23044)

While this doesn't solve the underlying problem, which will require an API breakage in `scaleOnRequestCount()` (see
aws#5667 (comment)).

As `scaleOnRequestCount()` seems to be the only part that is affected by this, we'll only issue a validation error if we have multiple `targetGroupArns` and `scaleOnRequestCount()` has been called.

closes aws#5667


----

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### Adding new Unconventional Dependencies:

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### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/main/INTEGRATION_TESTS.md)?
	* [ ] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

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

@@ -985,6 +985,7 @@ abstract class AutoScalingGroupBase extends Resource implements IAutoScalingGrou
   public abstract readonly osType: ec2.OperatingSystemType;
   protected albTargetGroup?: elbv2.ApplicationTargetGroup;
   public readonly grantPrincipal: iam.IPrincipal = new iam.UnknownPrincipal({ resource: this });
+  protected hasCalledScaleOnRequestCount: boolean = false;
 
   /**
    * Send a message to either an SQS queue or SNS topic when instances launch or terminate
@@ -1088,6 +1089,7 @@ abstract class AutoScalingGroupBase extends Resource implements IAutoScalingGrou
     });
 
     policy.node.addDependency(this.albTargetGroup.loadBalancerAttached);
+    this.hasCalledScaleOnRequestCount = true;
     return policy;
   }
 
@@ -1388,6 +1390,8 @@ export class AutoScalingGroup extends AutoScalingGroupBase implements
     if (props.requireImdsv2) {
       Aspects.of(this).add(new AutoScalingGroupRequireImdsv2Aspect());
     }
+
+    this.node.addValidation({ validate: () => this.validateTargetGroup() });
   }
 
   /**
@@ -1415,10 +1419,6 @@ export class AutoScalingGroup extends AutoScalingGroupBase implements
    * Attach to ELBv2 Application Target Group
    */
   public attachToApplicationTargetGroup(targetGroup: elbv2.IApplicationTargetGroup): elbv2.LoadBalancerTargetProps {
-    if (this.albTargetGroup !== undefined) {
-      throw new Error('Cannot add AutoScalingGroup to 2nd Target Group');
-    }
-
     this.targetGroupArns.push(targetGroup.targetGroupArn);
     if (targetGroup instanceof elbv2.ApplicationTargetGroup) {
       // Copy onto self if it's a concrete type. We need this for autoscaling
@@ -1765,6 +1765,16 @@ export class AutoScalingGroup extends AutoScalingGroupBase implements
       };
     }
   }
+
+
+  private validateTargetGroup(): string[] {
+    const errors = new Array<string>();
+    if (this.hasCalledScaleOnRequestCount && this.targetGroupArns.length > 1) {
+      errors.push('Cannon use multiple target groups if `scaleOnRequestCount()` is being used.');
+    }
+
+    return errors;
+  }
 }
 
 /**

packages/@aws-cdk/aws-autoscaling/package.json

@@ -82,10 +82,11 @@
   "devDependencies": {
     "@aws-cdk/assertions": "0.0.0",
     "@aws-cdk/cdk-build-tools": "0.0.0",
-    "@aws-cdk/integ-runner": "0.0.0",
     "@aws-cdk/cfn2ts": "0.0.0",
     "@aws-cdk/cloud-assembly-schema": "0.0.0",
     "@aws-cdk/cx-api": "0.0.0",
+    "@aws-cdk/integ-runner": "0.0.0",
+    "@aws-cdk/integ-tests": "0.0.0",
     "@aws-cdk/pkglint": "0.0.0",
     "@types/jest": "^27.5.2",
     "jest": "^27.5.1"

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

@@ -2,6 +2,7 @@ import { Annotations, Match, Template } from '@aws-cdk/assertions';
 import * as cloudwatch from '@aws-cdk/aws-cloudwatch';
 import * as ec2 from '@aws-cdk/aws-ec2';
 import { AmazonLinuxCpuType, AmazonLinuxGeneration, AmazonLinuxImage, InstanceType, LaunchTemplate } from '@aws-cdk/aws-ec2';
+import { ApplicationListener, ApplicationLoadBalancer, ApplicationTargetGroup } from '@aws-cdk/aws-elasticloadbalancingv2';
 import * as iam from '@aws-cdk/aws-iam';
 import * as sns from '@aws-cdk/aws-sns';
 import { testDeprecated } from '@aws-cdk/cdk-build-tools';
@@ -1864,6 +1865,61 @@ describe('auto scaling group', () => {
     })).not.toThrow();
 
   });
+
+  describe('multiple target groups', () => {
+    let asg: autoscaling.AutoScalingGroup;
+    let stack: cdk.Stack;
+    let vpc: ec2.IVpc;
+    let alb: ApplicationLoadBalancer;
+    let listener: ApplicationListener;
+
+    beforeEach(() => {
+      stack = new cdk.Stack(undefined, 'MyStack', { env: { region: 'us-east-1', account: '1234' } });
+      vpc = mockVpc(stack);
+      alb = new ApplicationLoadBalancer(stack, 'alb', {
+        vpc,
+        internetFacing: true,
+      });
+
+      listener = alb.addListener('Listener', {
+        port: 80,
+        open: true,
+      });
+
+      asg = new autoscaling.AutoScalingGroup(stack, 'MyFleet', {
+        instanceType: ec2.InstanceType.of(ec2.InstanceClass.M4, ec2.InstanceSize.MICRO),
+        machineImage: new ec2.AmazonLinuxImage(),
+        vpc,
+      });
+    });
+
+    test('Adding two application target groups should succeed validation', () => {
+      const atg1 = new ApplicationTargetGroup(stack, 'ATG1', { port: 443 });
+      const atg2 = new ApplicationTargetGroup(stack, 'ATG2', { port: 443 });
+
+      listener.addTargetGroups('tgs', { targetGroups: [atg1, atg2] });
+
+      asg.attachToApplicationTargetGroup(atg1);
+      asg.attachToApplicationTargetGroup(atg2);
+
+      expect(asg.node.validate()).toEqual([]);
+    });
+
+    test('Adding two application target groups should fail validation validate if `scaleOnRequestCount()` has been called', () => {
+      const atg1 = new ApplicationTargetGroup(stack, 'ATG1', { port: 443 });
+      const atg2 = new ApplicationTargetGroup(stack, 'ATG2', { port: 443 });
+
+      listener.addTargetGroups('tgs', { targetGroups: [atg1, atg2] });
+
+      asg.attachToApplicationTargetGroup(atg1);
+      asg.attachToApplicationTargetGroup(atg2);
+
+      asg.scaleOnRequestCount('requests-per-minute', { targetRequestsPerMinute: 60 });
+
+      expect(asg.node.validate()).toContainEqual('Cannon use multiple target groups if `scaleOnRequestCount()` is being used.');
+    });
+  });
+
 });
 
 function mockVpc(stack: cdk.Stack) {

packages/@aws-cdk/aws-autoscaling/test/integ.asg-w-elbv2.js.snapshot/LambdaTestDefaultTestDeployAssert1AF2B360.assets.json

@@ -0,0 +1,19 @@
+{
+  "version": "22.0.0",
+  "files": {
+    "21fbb51d7b23f6a6c262b46a9caee79d744a3ac019fd45422d988b96d44b2a22": {
+      "source": {
+        "path": "LambdaTestDefaultTestDeployAssert1AF2B360.template.json",
+        "packaging": "file"
+      },
+      "destinations": {
+        "current_account-current_region": {
+          "bucketName": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}",
+          "objectKey": "21fbb51d7b23f6a6c262b46a9caee79d744a3ac019fd45422d988b96d44b2a22.json",
+          "assumeRoleArn": "arn:${AWS::Partition}:iam::${AWS::AccountId}:role/cdk-hnb659fds-file-publishing-role-${AWS::AccountId}-${AWS::Region}"
+        }
+      }
+    }
+  },
+  "dockerImages": {}
+}

packages/@aws-cdk/aws-autoscaling/test/integ.asg-w-elbv2.js.snapshot/LambdaTestDefaultTestDeployAssert1AF2B360.template.json

@@ -0,0 +1,36 @@
+{
+ "Parameters": {
+  "BootstrapVersion": {
+   "Type": "AWS::SSM::Parameter::Value<String>",
+   "Default": "/cdk-bootstrap/hnb659fds/version",
+   "Description": "Version of the CDK Bootstrap resources in this environment, automatically retrieved from SSM Parameter Store. [cdk:skip]"
+  }
+ },
+ "Rules": {
+  "CheckBootstrapVersion": {
+   "Assertions": [
+    {
+     "Assert": {
+      "Fn::Not": [
+       {
+        "Fn::Contains": [
+         [
+          "1",
+          "2",
+          "3",
+          "4",
+          "5"
+         ],
+         {
+          "Ref": "BootstrapVersion"
+         }
+        ]
+       }
+      ]
+     },
+     "AssertDescription": "CDK bootstrap stack version 6 required. Please run 'cdk bootstrap' with a recent version of the CDK CLI."
+    }
+   ]
+  }
+ }
+}

packages/@aws-cdk/aws-autoscaling/test/integ.asg-w-elbv2.js.snapshot/aws-cdk-asg-atg-integ.assets.json

@@ -0,0 +1,19 @@
+{
+  "version": "22.0.0",
+  "files": {
+    "6e4ba6d1c10cb8a0be78abd30ef94d231f8913f1cd4b02c0b62b8626f3425c00": {
+      "source": {
+        "path": "aws-cdk-asg-atg-integ.template.json",
+        "packaging": "file"
+      },
+      "destinations": {
+        "current_account-current_region": {
+          "bucketName": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}",
+          "objectKey": "6e4ba6d1c10cb8a0be78abd30ef94d231f8913f1cd4b02c0b62b8626f3425c00.json",
+          "assumeRoleArn": "arn:${AWS::Partition}:iam::${AWS::AccountId}:role/cdk-hnb659fds-file-publishing-role-${AWS::AccountId}-${AWS::Region}"
+        }
+      }
+    }
+  },
+  "dockerImages": {}
+}