> ## 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.

# Create FIS Experiment

> This guide explains how to define and launch an AWS FIS experiment using actions, targets, and stop conditions while applying guardrails.

AWS Fault Injection Simulator (FIS) helps you test the resilience of your applications by safely inducing faults. In this guide, we’ll define and launch an FIS experiment using three core components: **Actions**, **Targets**, and **Stop Conditions**. You’ll also learn how to apply guardrails to contain the blast radius.

***

## Table of Contents

1. [Core Components](#core-components)
2. [Prerequisites](#prerequisites)
3. [Step 1: Define the Action](#step-1-define-the-action)
4. [Step 2: Specify the Target](#step-2-specify-the-target)
5. [Step 3: Add a Stop Condition](#step-3-add-a-stop-condition)
6. [Step 4: Launch the Experiment](#step-4-launch-the-experiment)
7. [Cleanup](#cleanup)
8. [Links and References](#links-and-references)

***

## Core Components

| Component          | Description                                                                               | Example                                       |
| ------------------ | ----------------------------------------------------------------------------------------- | --------------------------------------------- |
| **Action**         | The fault you inject into the system.                                                     | Terminating an EC2 instance                   |
| **Target**         | The resource(s) on which the action runs.                                                 | EC2 instances identified by tag `Service=api` |
| **Stop Condition** | A criterion—such as a CloudWatch alarm—that halts and rolls back the experiment when met. | CPU utilization > 80% for 5 minutes           |

<Callout icon="lightbulb" color="#1CB2FE">
  Stop conditions are optional but **strongly recommended**. They prevent runaway experiments and ensure safety.
</Callout>

***

## Prerequisites

* AWS CLI v2 installed and configured
* IAM role with permissions:
  * `fis:CreateExperimentTemplate`
  * `fis:StartExperiment`
  * `ec2:TerminateInstances`
  * `cloudwatch:DescribeAlarms`
* EC2 instances tagged with `FaultInject=true`

***

## Step 1: Define the Action

We’ll terminate EC2 instances tagged for the experiment. Use the following snippet in your experiment template:

```json theme={null}
"actions": {
  "terminateInstances": {
    "actionId": "aws:ec2:terminate-instances",
    "description": "Terminate targeted EC2 instances",
    "parameters": {
      "instances": ["${TargetInstanceIDs}"]
    }
  }
}
```

***

## Step 2: Specify the Target

Identify EC2 instances by tag. You can also use resource IDs or ARNs.

```json theme={null}
"targets": {
  "TargetInstanceIDs": {
    "resourceType": "aws:ec2:instance",
    "resourceTags": {
      "FaultInject": "true"
    }
  }
}
```

***

## Step 3: Add a Stop Condition

Define a CloudWatch alarm that stops the experiment when CPU usage exceeds 80% for 5 minutes:

```json theme={null}
"stopConditions": [
  {
    "source": "aws:cloudwatch:alarm",
    "value": "arn:aws:cloudwatch:us-east-1:123456789012:alarm:HighCPUAlarm"
  }
]
```

<Callout icon="triangle-alert" color="#FF6B6B">
  Ensure your CloudWatch alarm ARN is correct. A misconfigured stop condition may not trigger, leaving experiments running longer than intended.
</Callout>

***

## Step 4: Launch the Experiment

Combine the components into a single template and create it with the AWS CLI:

```bash theme={null}
aws fis create-experiment-template \
  --tags Name=TerminateEC2Test \
  --description "Terminate EC2 instances with guardrails" \
  --role-arn arn:aws:iam::123456789012:role/AWSFISRole \
  --actions file://actions.json \
  --targets file://targets.json \
  --stop-conditions file://stop-conditions.json
```

Once the template is created, start the experiment:

```bash theme={null}
aws fis start-experiment \
  --experiment-template-id et-0123456789abcdef0
```

***

## Cleanup

After testing, delete your experiment template to avoid orphaned resources:

```bash theme={null}
aws fis delete-experiment-template \
  --experiment-template-id et-0123456789abcdef0
```

***

## Links and References

* [AWS Fault Injection Simulator Developer Guide](https://docs.aws.amazon.com/fis/latest/userguide/)
* [AWS CLI Command Reference: FIS](https://docs.aws.amazon.com/cli/latest/reference/fis/index.html)
* [Creating CloudWatch Alarms](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/AlarmThatSendsEmail.html)

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