How to stop/start an EC2 instance on a schedule within an autoscale group without terminating the instance?

Question

If you have have an autoscaling group, how do you go about start/stopping the instances (not launch/terminate) ? The default behaviour is only for launching an

Answer 1

First and foremost, the AWS autoscaling group is a container for multiple instances that are based on a launch configuration. If we are able to disable the processes that trigger up/down scaling, we are back to the container that just holds instances.

In order to disable these processes, we need to use the suspend-processes command from AWS-CLI. For this example, I will use powershell, but its just as easy to write in bash:

# suspend HealthCheck and ReplaceUnhealthy processes, you may find another combination works better for you.
$asGroup = "nameOfYourAutoScalingGroup" ;
aws autoscaling suspend-processes `
    --auto-scaling-group-name $asGroup `
    --scaling-processes HealthCheck ReplaceUnhealthy ;

# verify the change
awsp autoscaling describe-auto-scaling-groups `
    --auto-scaling-group-name $asGroup ;

For my purposes, I wanted the instances to be online between 7am and 7pm to reduce costs. These instances are used between our development and QA teams, and they prefer to keep the state of the server from day to day.

NOTE: in the circumstance where the EC2 instance becomes corrupt or accidentally terminated, our team is fine with rollbacking back to the latest AMI (they really just want the logs to persist, but if they are lost, it isn't the end of the world)

Next we'll require a script to start/stop the servers, here I have it as 2 scripts, but you can easily optimize it into one script and pass an argument in:

# in our case, we want to perform this to all autoscaling groups
# you'll need Powershell 3.0+ in order to use ConvertFrom-Json
$asGroups = aws autoscaling describe-auto-scaling-groups --query 'AutoScalingGroups[*].{Name:AutoScalingGroupName,Instances:Instances[*].InstanceId}' ;
$asGroups = "{ asGroups: $asGroups }" | ConvertFrom-Json ;

# foreach autoscaling group, go through each instance and start
foreach ($asGroup in $($asGroups.asGroups)) {

    echo "AS: $($asGroup.Name)" ;
    foreach ($instance in $asGroup.instances) {
        echo "starting instance: $instance";
        aws ec2 start-instances `
            --instance-ids $instance ;
    }
}

# in our case, we want to perform this to all autoscaling groups
# you'll need Powershell 3.0+ in order to use ConvertFrom-Json
$asGroups = awsp autoscaling describe-auto-scaling-groups --query 'AutoScalingGroups[*].{Name:AutoScalingGroupName,Instances:Instances[*].InstanceId}' ;
$asGroups = "{ asGroups: $asGroups }" | ConvertFrom-Json ;

# foreach autoscaling group, go through each instance and stop
foreach ($asGroup in $($asGroups.asGroups)) {

    echo "AS: $($asGroup.Name)" ;
    foreach ($instance in $asGroup.instances) {
        echo "stopping instance: $instance";
        awsp ec2 stop-instances `
            --instance-ids $instance ;
    }
}

The last step would be to add it to the Scheduled Tasks on a control server (I'm currently just using my desktop which never turns off). Attached is an example of the exported Schedule Task, runs weekly Mon, Tue, Wed, Thurs, Friday at 7am.

  
    2014-08-22T13:13:02.2103946
    localhost\Administrator
  
  
    
      2014-08-22T07:00:00
      true
      
        
          
          
          
          
          
        
        1
      
    
  
  
    
      localhost\Administrator
      InteractiveToken
      LeastPrivilege
    
  
  
    IgnoreNew
    true
    true
    true
    false
    false
    
      true
      false
    
    true
    true
    false
    false
    false
    P3D
    7
  
  
    
      C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
      -ExecutionPolicy ByPass c:\tasks\AWS-Autoscaling-EC2-Start-Morning.ps1
      c:\tasks
    
  

You'll need to make the "Stop" version of this task to stop servers at 7pm. Just change your start boundary to 2014-08-22T19:00:00 and update -ExecutionPolicy ByPass c:\tasks\AWS-Autoscaling-EC2-Start-Morning.ps1 to the correct ps1.