EC2 Auto Scaling Group Simple Scaling policy with AWS CLI

Here I will show you how to configure Simple Scaling Policy for EC2 Auto Scaling Group with AWS CLI.

Simple Scaling Policy with CloudWatch alarms

Amazon EC2 Auto Scaling Group supports 3 types of dynamic scaling --
1. Target Tracking Scaling
2. Simple Scaling
3. Step Scaling

Simple Scaling:

Simple scaling policy allows you to define CloudWatch alarms based on which scale in/out is triggered. Instances can be added or removed from the Auto Scaling Group or can be set to achieve a desired capacity with each alarms action.

Here I will configure the scale out and scale in for high CPU usage alert and low CPU usage alert respectively.

Let’s start -

Step 1: Create an EC2 Launch Template

#Please modify the parameters before execution
aws ec2 create-launch-template \
     --launch-template-name AutoScaleLaunchTemplate \
     --version-description Version_1 \
     --region us-east-1 \
     --launch-template-data '{ "NetworkInterfaces": [{ "DeviceIndex": 0, "Groups": ["sg-05e7a69c323bdd40f"] }], "ImageId": "ami-02e136e904f3da870", "InstanceType": "t2.micro", "KeyName": "EC2KeyPair" }'

Step 2: Deploy the Auto Scaling Group

#Please modify the parameters before execution
aws autoscaling create-auto-scaling-group \
     --auto-scaling-group-name DemoAutoScalingGroup \
     --launch-template LaunchTemplateId=lt-0e321233cce2818d2 \
     --min-size 1 \
     --max-size 4\
     --vpc-zone-identifier "subnet-00db35de81dff856b,subnet-0c4c6c468be60a37f,subnet-08b515f135d99437e"

EC2 Auto Scaling Group created

Step 3: Configure the Simple Scaling policies

Execute the below script to set a scale out policy. It will increase the capacity of the auto scaling group by 1.

#Scale out policy 
aws autoscaling put-scaling-policy \
    --policy-name demoSimpleScaleOutPolicy \
    --auto-scaling-group-name DemoAutoScalingGroup \
    --scaling-adjustment +1 \
    --adjustment-type ChangeInCapacity

Execute the below script to set a scale in policy. It will decrease the capacity of the auto scaling group by 1.

#Scale in policy
aws autoscaling put-scaling-policy \
    --policy-name demoSimpleScaleInPolicy \
    --auto-scaling-group-name DemoAutoScalingGroup \
    --scaling-adjustment -1 \
    --adjustment-type ChangeInCapacity \
    --cooldown 180

Copy the both Policy ARN, will be used in the next steps.

Step 4: Create and associate CloudWatch alarms with the policies

Below script will create a CloudWatch alarm which will be triggered if the Average CPU utilization of the Auto Scaling Group goes above or at 70% for at least 3 consecutive evaluation periods of 3 minutes. Scale out policy will be in action whenever this alarm gets triggered.

#CloudWatch Alarm for scale out
aws cloudwatch put-metric-alarm \
    --alarm-name SimpleScalingAlarmHighAddCapacity \
    --metric-name CPUUtilization \
    --namespace AWS/EC2 --statistic Average \
    --period 180 --evaluation-periods 3 --threshold 70 \
    --comparison-operator GreaterThanOrEqualToThreshold \
    --dimensions "Name=AutoScalingGroupName, Value=DemoAutoScalingGroup" \
    --alarm-actions "arn:aws:autoscaling:us-east-1:XXXXYYYYZZZZZ:scalingPolicy:43ed4879-a778-41d5-8e51-53740bc7c7c7:autoScalingGroupName/DemoAutoScalingGroup:policyName/demoSimpleScaleOutPolicy"

Below script will create a CloudWatch alarm which will be triggered if the Average CPU utilization of the Auto Scaling Group goes below or at 50% for at least 3 consecutive evaluation periods of 3 minutes. Scale in policy will be in action whenever this alarm gets triggered.

#CloudWatch Alarm for scale in
aws cloudwatch put-metric-alarm \
    --alarm-name SimpleScalingAlarmHighRemoveCapacity \
    --metric-name CPUUtilization \
    --namespace AWS/EC2 --statistic Average \
    --period 180 --evaluation-periods 3 --threshold 50 \
    --comparison-operator LessThanOrEqualToThreshold \
    --dimensions "Name=AutoScalingGroupName, Value=DemoAutoScalingGroup" \
    --alarm-actions "arn:aws:autoscaling:us-east-1:XXXXYYYYZZZZ:scalingPolicy:3ea5a0cf-14e5-40d3-82b3-b02159464bae:autoScalingGroupName/DemoAutoScalingGroup:policyName/demoSimpleScaleInPolicy"

Simple Scaling Policies configured

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Thank you for reading this. Enjoy and also read my other blogs of EC2 Auto Scaling setup with AWS CLI.

Configure Scheduled Scaling Actions for EC2 Auto Scaling Group with AWS CLI

EC2 Auto Scaling Target Tracking Policy with AWS CLI