> ## 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 FIS experiment CloudWatch Dashboard

> This lesson demonstrates using a CloudWatch dashboard to monitor an Auto Scaling Group during a Fault Injection Simulator experiment.

In this lesson, we’ll leverage a pre-configured [Amazon CloudWatch](https://aws.amazon.com/cloudwatch/) dashboard to monitor an [Auto Scaling Group (ASG)](https://docs.aws.amazon.com/autoscaling/ec2/userguide/auto-scaling-groups.html) during a [Fault Injection Simulator (FIS)](https://aws.amazon.com/fis/) experiment. This setup provides real-time insights into ELB health checks and ASG instance status, enabling you to track scaling behavior and resilience under controlled failures.

<Callout icon="lightbulb" color="#1CB2FE">
  * An AWS FIS experiment configured to terminate or impair EC2 instances
  * An ASG with `minCapacity` set to a desired level
  * A CloudWatch dashboard pre-populated with the relevant widgets
</Callout>

## Dashboard Widgets Overview

| Widget Name          | Metrics Displayed                        | Purpose                                    |
| -------------------- | ---------------------------------------- | ------------------------------------------ |
| ELB Host HealthCheck | Healthy vs. unhealthy instances          | Monitors ELB health check results          |
| ASG Instance Checks  | Total, pending, and in-service instances | Tracks scaling events and lifecycle status |

## How to Interpret the Charts

1. **ELB Host HealthCheck**
   * **Baseline**: Starts with 2 healthy instances.
   * **During FIS**: One instance is terminated → healthy count drops to 1.
   * **Recovery**: ASG’s `minCapacity=2` triggers a replacement → healthy count returns to 2.

2. **ASG Instance Checks**
   * **Pending**: Instances being initialized after launch.
   * **InService**: Fully operational, serving traffic.
   * The graph pattern mirrors the ELB health trend, reflecting when the ASG spins up replacement instances.

<Frame>
  ![The image shows a dashboard with two graphs: one for ELB Host HealthCheck displaying healthy and unhealthy counts, and another for ASG Instance Checks showing total, pending, and in-service instances over time.](https://kodekloud.com/kk-media/image/upload/v1752871783/notes-assets/images/Chaos-Engineering-Demo-FIS-experiment-CloudWatch-Dashboard/elb-healthcheck-asg-instance-dashboard.jpg)
</Frame>

<Callout icon="triangle-alert" color="#FF6B6B">
  If you terminate multiple instances at once or set a high desired capacity, the ASG may launch many replacements simultaneously. Monitor the **ASG Instance Checks** widget to avoid unexpected resource costs.
</Callout>

## Conclusion

By correlating the ELB Host HealthCheck and ASG Instance Checks charts, you gain a clear, real-time view of how FIS-induced failures impact instance health and auto scaling. This dashboard becomes a powerful tool for validating the resiliency and fault tolerance of your AWS infrastructure.

## References

* [Amazon CloudWatch](https://aws.amazon.com/cloudwatch/)
* [AWS Fault Injection Simulator (FIS)](https://aws.amazon.com/fis/)
* [Auto Scaling Groups](https://docs.aws.amazon.com/autoscaling/ec2/userguide/auto-scaling-groups.html)

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