In CDK, how do you enable `associatePublicIpAddress` in an AutoScalingGroup that has a `mixedInstancesPolicy`?

Question

I'm using AWS CDK and am trying to enable the associatePublicIpAddress property for an AutoScalingGroup that's using a launch template.

My first attempt was to just set `associatePublicIpAddress: true`, but I get this error (https://github.com/aws/aws-cdk/blob/master/packages/%40aws-cdk/aws-autoscaling/lib/auto-scaling-group.ts#L1526-L1528)

```typescript
// first attempt
new asg.AutoScalingGroup(this, 'ASG', {
  associatePublicIpAddress: true, // here
  minCapacity: 1,
  maxCapacity: 1,
  vpc,
  vpcSubnets: {
    subnetType: SubnetType.PUBLIC,
    onePerAz: true,
    availabilityZones: [availabilityZone],
  },
  mixedInstancesPolicy: {
    instancesDistribution: {
      spotMaxPrice: '1.00',
      onDemandPercentageAboveBaseCapacity: 0,
    },
    launchTemplate: new LaunchTemplate(this, 'LaunchTemplate', {
      securityGroup: this._securityGroup,
      role,
      instanceType
      machineImage,
      userData: UserData.forLinux(),
    }),
    launchTemplateOverrides: [
      {
        instanceType: InstanceType.of(
          InstanceClass.T4G,
          InstanceSize.NANO
        ),
      },
    ],
  },
  keyName,
})
```

```typescript
// I hit this error from the CDK
    if (props.associatePublicIpAddress) {
      throw new Error('Setting \'associatePublicIpAddress\' must not be set when \'launchTemplate\' or \'mixedInstancesPolicy\' is set');
    }
```

My second attempt was to not set `associatePublicIpAddress` and see if it gets set automatically because the AutoScalingGroup is in a public availablity zone with an internet gateway. However, it still doesn't provision a public ip address.

Has anyone been able to create an autoscaling group with a mix instance policy and an associated public ip?

Accepted Answer

You're setting associatePublicIpAddress on the ASG. You need to either set it on the launch template; or change the subnets default behavior to associatePublicIpAddress=true. Just having an IGW doesn't automatically change this setting for the subnet, and the default is false except for the default subnets in your default VPC

The code function you linked is called "verifyNoLaunchConfigPropIsGiven"; meaning those properties were for launch configurations (the older feature that has since been replaced by launch templates)

In CDK, how do you enable `associatePublicIpAddress` in an AutoScalingGroup that has a `mixedInstancesPolicy`?

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