> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Demo Creating a composite alarm
> This article provides a step-by-step guide to creating a composite alarm in AWS using CloudFormation, including resource provisioning and alarm configuration.
## Prerequisites
Ensure you define the `LatestAmiId` parameter before deploying the stack. For example:
```yaml theme={null}
Parameters:
LatestAmiId:
Type: AWS::SSM::Parameter::Value
Default: /aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2
```
## CloudFormation Template Overview
This CloudFormation template provisions the following AWS resources:
| Resource | Description | CloudFormation Type |
| ----------------------------- | --------------------------------------------------- | ------------------------------------- |
| Security Group | SSH access for EC2 instances | AWS::EC2::SecurityGroup |
| Launch Configuration | Launches `t2.micro` instances with latest AMI | AWS::AutoScaling::LaunchConfiguration |
| Auto Scaling Group (ASG) | Scales between 2 and 20 instances, 1-minute metrics | AWS::AutoScaling::AutoScalingGroup |
| Scale-Up Policy | Increases ASG capacity by 1 instance | AWS::AutoScaling::ScalingPolicy |
| CloudWatch Alarm: HighCPU | Triggers when CPU > 80% | AWS::CloudWatch::Alarm |
| CloudWatch Alarm: VeryHighCPU | Triggers when CPU > 90% | AWS::CloudWatch::Alarm |
| CloudWatch Alarm: HighASGSize | Triggers when ASG size > 10 | AWS::CloudWatch::Alarm |
### Core Resources
```yaml theme={null}
Resources:
MyEC2SecurityGroup:
Type: 'AWS::EC2::SecurityGroup'
Properties:
GroupDescription: EC2 Security Group for the Auto Scaling Group instances
SecurityGroupIngress:
- IpProtocol: tcp
FromPort: '22'
ToPort: '22'
CidrIp: 0.0.0.0/0
LaunchConfiguration:
Type: 'AWS::AutoScaling::LaunchConfiguration'
Properties:
ImageId: !Ref LatestAmiId
InstanceType: t2.micro
SecurityGroups:
- Ref: MyEC2SecurityGroup
AutoScalingGroup:
Type: 'AWS::AutoScaling::AutoScalingGroup'
Properties:
AvailabilityZones: Fn::GetAZs: ''
LaunchConfigurationName: Ref: LaunchConfiguration
MinSize: '2'
MaxSize: '20'
DesiredCapacity: '2'
MetricsCollection:
- Granularity: 1Minute
ScaleUpPolicy:
Type: 'AWS::AutoScaling::ScalingPolicy'
Properties:
AutoScalingGroupName: Ref: AutoScalingGroup
AdjustmentType: ChangeInCapacity
ScalingAdjustment: '1'
Cooldown: '300'
```
### CloudWatch Alarms Definition
| Alarm Name | Metric | Threshold | Period | Namespace |
| ---------------- | ------------------- | --------- | ------ | --------------- |
| HighCPUUsage | CPUUtilization | 80% | 300s | AWS/EC2 |
| VeryHighCPUUsage | CPUUtilization | 90% | 300s | AWS/EC2 |
| HighASGSize | GroupTotalInstances | 10 | 300s | AWS/AutoScaling |
```yaml theme={null}
HighCPUAlarm:
Type: 'AWS::CloudWatch::Alarm'
Properties:
AlarmName: HighCPUUsage
AlarmDescription: Alarm when CPU exceeds 80 percent
Namespace: AWS/EC2
MetricName: CPUUtilization
Statistic: Average
Period: '300'
EvaluationPeriods: '1'
Threshold: '80'
ComparisonOperator: GreaterThanThreshold
Dimensions:
- Name: AutoScalingGroupName
Value: Ref: AutoScalingGroup
VeryHighCPUAlarm:
Type: 'AWS::CloudWatch::Alarm'
Properties:
AlarmName: VeryHighCPUUsage
AlarmDescription: Alarm when CPU exceeds 90 percent
Namespace: AWS/EC2
MetricName: CPUUtilization
Statistic: Average
Period: '300'
EvaluationPeriods: '1'
Threshold: '90'
ComparisonOperator: GreaterThanThreshold
Dimensions:
- Name: AutoScalingGroupName
Value: Ref: AutoScalingGroup
HighASGSizeAlarm:
Type: 'AWS::CloudWatch::Alarm'
Properties:
AlarmName: HighASGSize
AlarmDescription: Alarm when ASG size exceeds 10
Namespace: AWS/AutoScaling
MetricName: GroupTotalInstances
Statistic: Average
Period: '300'
EvaluationPeriods: '1'
Threshold: '10'
ComparisonOperator: GreaterThanThreshold
Dimensions:
- Name: AutoScalingGroupName
Value: Ref: AutoScalingGroup
```
### Outputs
```yaml theme={null}
Outputs:
AutoScalingGroupName:
Description: The name of the Auto Scaling Group
Value: Ref: AutoScalingGroup
```
Although the ASG can scale up to 20 instances, our threshold is set at >10 for demonstration.
## Deploy the CloudFormation Stack
1. Open the AWS [CloudFormation Console](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/).
2. Choose **Create stack** > **Upload a template file**, and select your `composite_alarm.yaml`.
3. Click **Next**, set **Stack name** to `CompositeAlarmInfra`, and keep default parameters.
4. Submit and wait \~4–5 minutes until status is `CREATE_COMPLETE`.
5. On **Outputs**, copy the **AutoScalingGroupName**.
## Verify CloudWatch Alarms
Navigate to **CloudWatch > Alarms**. You should see:
* **HighASGSize**
* **HighCPUUsage**
* **VeryHighCPUUsage**
Initial states will be `OK` or `Insufficient Data`.
## Create the Composite Alarm
1. Select the three child alarms.
2. Go to **Actions > Create composite alarm**.
3. Define the rule:
```text theme={null}
ALARM(HighCPUUsage) OR ALARM(VeryHighCPUUsage) OR ALARM(HighASGSize)
```
4. Configure notifications (e.g., an SNS topic) and an optional suppressor alarm.
5. Enter **Name** and **Description** (Markdown supported).
After creation, you’ll see four alarms, all in `OK` state.
## Test the Composite Alarm
To trigger the alarm:
1. In the EC2 Console, open your ASG > **Details** > **Edit**.
2. Set **Min** and **Desired** capacity to `12`, then save.
After one metric period, **HighASGSize** will fire and the composite alarm will trigger.
Check your email for the SNS notification.
## Cleanup
1. Delete the CloudFormation stack.
2. In CloudWatch, select the composite alarm and choose **Actions > Delete**.
Deleting the composite alarm must be done manually—it is not removed by the CloudFormation stack.
This completes the guide to building and testing an AWS composite alarm using CloudFormation, Auto Scaling, and CloudWatch.