# CfnAutoScalingRollingUpdate

To specify how AWS CloudFormation handles rolling updates for an Auto Scaling group, use the AutoScalingRollingUpdate policy.

Rolling updates enable you to specify whether AWS CloudFormation updates instances that are in an Auto Scaling
group in batches or all at once.

- Source: [`core/lib/cfn-resource-policy.ts`](https://github.com/aws/aws-cdk/blob/v2.274.0/packages/aws-cdk-lib/core/lib/cfn-resource-policy.ts#L173)
- Type last changed: v2.188.0 · 4 Apr 2025

## Example

```ts
// The code below shows an example of how to instantiate this type.
// The values are placeholders you should change.
import * as cdk from 'aws-cdk-lib';
const cfnAutoScalingRollingUpdate: cdk.CfnAutoScalingRollingUpdate = {
  maxBatchSize: 123,
  minActiveInstancesPercent: 123,
  minInstancesInService: 123,
  minSuccessfulInstancesPercent: 123,
  pauseTime: 'pauseTime',
  suspendProcesses: ['suspendProcesses'],
  waitOnResourceSignals: false,
};
```

## Properties

- `maxBatchSize`: number — Specifies the maximum number of instances that AWS CloudFormation updates.

- `minActiveInstancesPercent`: number — Specifies the percentage of instances in an Auto Scaling group that must remain in service while AWS CloudFormation updates old instances.

  You can specify a value from 0 to 100. AWS CloudFormation rounds to the nearest tenth of a percent.
  For example, if you update five instances with a minimum active percentage of 50, three instances must remain in service.

- `minInstancesInService`: number — Specifies the minimum number of instances that must be in service within the Auto Scaling group while AWS CloudFormation updates old instances.

- `minSuccessfulInstancesPercent`: number — Specifies the percentage of instances in an Auto Scaling rolling update that must signal success for an update to succeed.

  You can specify a value from 0 to 100. AWS CloudFormation rounds to the nearest tenth of a percent. For example, if you
  update five instances with a minimum successful percentage of 50, three instances must signal success.

  If an instance doesn't send a signal within the time specified in the PauseTime property, AWS CloudFormation assumes
  that the instance wasn't updated.

  If you specify this property, you must also enable the WaitOnResourceSignals and PauseTime properties.

- `pauseTime`: string — The amount of time that AWS CloudFormation pauses after making a change to a batch of instances to give those instances time to start software applications.

  For example, you might need to specify PauseTime when scaling up the number of
  instances in an Auto Scaling group.

  If you enable the WaitOnResourceSignals property, PauseTime is the amount of time that AWS CloudFormation should wait
  for the Auto Scaling group to receive the required number of valid signals from added or replaced instances. If the
  PauseTime is exceeded before the Auto Scaling group receives the required number of signals, the update fails. For best
  results, specify a time period that gives your applications sufficient time to get started. If the update needs to be
  rolled back, a short PauseTime can cause the rollback to fail.

  Specify PauseTime in the ISO8601 duration format (in the format PT#H#M#S, where each # is the number of hours, minutes,
  and seconds, respectively). The maximum PauseTime is one hour (PT1H).

- `suspendProcesses`: string[] — Specifies the Auto Scaling processes to suspend during a stack update.

  Suspending processes prevents Auto Scaling from
  interfering with a stack update. For example, you can suspend alarming so that Auto Scaling doesn't execute scaling
  policies associated with an alarm. For valid values, see the ScalingProcesses.member.N parameter for the SuspendProcesses
  action in the Auto Scaling API Reference.

- `waitOnResourceSignals`: boolean — Specifies whether the Auto Scaling group waits on signals from new instances during an update.

  Use this property to
  ensure that instances have completed installing and configuring applications before the Auto Scaling group update proceeds.
  AWS CloudFormation suspends the update of an Auto Scaling group after new EC2 instances are launched into the group.
  AWS CloudFormation must receive a signal from each new instance within the specified PauseTime before continuing the update.
  To signal the Auto Scaling group, use the cfn-signal helper script or SignalResource API.

  To have instances wait for an Elastic Load Balancing health check before they signal success, add a health-check
  verification by using the cfn-init helper script. For an example, see the verify_instance_health command in the Auto Scaling
  rolling updates sample template.