(aws-autoscaling): Build guardrail to prevent availability risk by instance profile deletion/recreation during migration to LT #34283
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jungseoklee
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bug
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bot
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@aws-cdk/aws-autoscaling
|
Hey, thank you for reporting this issue regarding the potential availability risk during migration from Launch Configuration to Launch Template. Current behavior:
// In AutoScalingGroup constructor when using Launch Configuration
const iamProfile = new iam.CfnInstanceProfile(this, 'InstanceProfile', {
roles: [this.role.roleName],
});
// In LaunchTemplate constructor
const iamProfile = new iam.CfnInstanceProfile(this, 'Profile', {
roles: [this.role.roleName],
});
Users can currently mitigate this issue by explicitly specifying a rolling update policy when migrating: // When migrating from Launch Configuration to Launch Template
new autoscaling.AutoScalingGroup(this, 'ASG', {
// ... other properties ...
launchTemplate: myLaunchTemplate,
updatePolicy: autoscaling.UpdatePolicy.rollingUpdate({
maxBatchSize: 1,
minInstancesInService: 1,
pauseTime: Duration.minutes(5),
waitOnResourceSignals: true,
}),
});This ensures instances are properly replaced during the migration, preventing the availability issue. I do agree with your proposed solution to add a Instead of automatically applying a default rolling update policy (which might not be suitable for all users), the property could enforce that users explicitly define their own rolling update policy: // In the AutoScalingGroup constructor
if (props.migrateToLaunchTemplate === true && !props.updatePolicy) {
throw new ValidationError(
'When migrateToLaunchTemplate is true, you must also provide an updatePolicy ' +
'to ensure instances are properly replaced during migration. ' +
'This prevents instances from referencing a deleted IAM instance profile. ' +
'Use UpdatePolicy.rollingUpdate() to define your rolling update settings.',
this
);
}This approach: If you are interested in implementing this feature, please feel free to open a Pull Request. The contribution guidelines can be found here. Marking as feature request P2 |
ykethan
added
p2
feature-request
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Thanks for taking a look! Your understanding is correct, and I agree with your suggestion. |
Describe the bug
Hi CDK community,
Today, AutoScalingGroup construct creates IAM instance profile using role provided by a customer. When a customer updates an existing Auto Scaling group associated with Launch Configuration to use Launch Template, i.e. passing Launch Template as an input for AutoScalingGroup construct AND creates Launch Template using role, IAM instance profile is deleted and re-created due to change in CFN logical ID. If IAM instance profile is referenced, it can end up with losing access.
This issue is about addressing the risk in AutoScalingGroup construct by building safety guardrail, e.g. enforcing RollingUpdate or throwing validation error.
Regression Issue
Last Known Working CDK Version
No response
Expected Behavior
An deleted IAM instance profile should not be referenced.
Current Behavior
An deleted IAM instance profile is referenced.
Reproduction Steps
role.AUTOSCALING_GENERATE_LAUNCH_TEMPLATEfeature flag.role.Possible Solution
A high-level proposal is to enforce RollingUpdate when migrating Launch Template from Launch Configuration. Here are implementation details:
migrateToLaunchTemplate?attribute to AutoScalingGroup construct.UpdatePolicy.rollingUpdate()whenmigrateToLaunchTemplateis true.In this way, we can guarantee that existing EC2 instances based on Launch Configuration are terminated and new EC2 instances based on Launch Template are launched, which always uses IAM instance profile defined by Launch Template.
Additional Information/Context
No response
CDK CLI Version
Applicable to every versions before AutoScalingGroup is created with Launch Template by default
Framework Version
No response
Node.js Version
Applicable to every version
OS
Applicable to every OS
Language
TypeScript
Language Version
No response
Other information
No response
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