Feature Request: Change EC2 instance type more easily

Question

I often change the EC2 instance type using the AWS CLI:

```
# Instance is currently running.
aws ec2 stop-instances --instance-ids i-SOMEID
# Wait up to a few minutes till the instance has shut down.
aws ec2 modify-instance-attribute --instance-id i-SOMEID --instance-type "{\"Value\": \"t3.xlarge\"}"
aws ec2 start-instances --instance-ids i-SOMEID
# Wait a few minutes
# The instance is running again.
```

However, it takes a while (up to a few minutes) for the instance to stop. Only when it is stopped, I can change the instance type and start it again. Otherwise, I get `An error occurred (IncorrectInstanceState) when calling the ModifyInstanceAttribute operation: The instance 'i-SOMEID' is not in the 'stopped' state.`

It would be great if I could stop the instance, switch the instance type, and start it again by running the 3 commands directly after the other. Then waiting a few minutes is ok, I just want the two wait times to be merged into one.

Accepted Answer

There are a few options.

Assuming your EC2 instance is being [managed by Systems Manager](https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-setting-up-ec2.html), you can use Systems Manager  [AWS-ResizeInstance](https://docs.aws.amazon.com/systems-manager-automation-runbooks/latest/userguide/automation-aws-resizeinstance.html) to change instance type. The console provides AWS CLI command to run, e.g. 
```
aws ssm start-automation-execution --document-name "AWS-ResizeInstance" --document-version "\$DEFAULT" --parameters '{"InstanceId":["i-XXXXX"],"InstanceType":["m7g.xlarge"],"SleepWait":["PT5S"],"AutomationAssumeRole":[""]}' --region ap-southeast-1
```

Since you are a developer, perhaps modify your script to get EC2 InstanceState. Wait for InstanceState to change from **running** to **stopped** before you execute start-instance
```
 aws ec2 describe-instance-status --instance-ids i-XXXXXXXX
{
    "InstanceStatuses": [
        {
            "AvailabilityZone": "ap-southeast-1a",
            "InstanceId": "i-XXXXXXXX",
            "InstanceState": {
                "Code": 16,
                "Name": "running"
            },
```

Or you can use Python to do it. Code is something like below (Reference: https://medium.com/@hasnain.hakim25/change-the-instance-type-in-aws-using-python-with-custom-metrics-memory-and-lambda-function-14f9ca5c9b77)

```
import boto3
import time

client = boto3.client('ec2')
ec2_instance = 'i-XXXXXXXX'
    
client.stop_instances(InstanceIds=[my_instance])
waiter=client.get_waiter('instance_stopped')
waiter.wait(InstanceIds=[my_instance])
    
client.modify_instance_attribute(InstanceId=ec2_instance, Attribute='instanceType', Value='t3.large')
    
 client.start_instances(InstanceIds=[my_instance])
  ```

Answer

Hello.

How about managing EC2 with CloudFormation?  
By managing EC2 with CloudFormation, you can restart the instance just by changing the instance type parameters within CloudFormation.

Feature Request: Change EC2 instance type more easily

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