AWS Fault Injection Service: Simulate Outages, Test Resilience

AWS Fault Injection Service (FIS) helps you test your AWS systems' resilience by simulating controlled disruptions. Here's what you need to know:

Purpose: Find and fix weak spots in your applications before real outages occur
Key features:
- Simulate resource disruptions, API issues, network problems, and resource stress
- Target specific parts of your system
- Work with other AWS tools like CloudWatch and IAM

To get started:

Set up your AWS account and IAM permissions
Create test resources (VPC, EC2 instances, RDS databases)
Make an experiment template
Run your first test
Analyze results and improve your system

Test Scenario	What It Does	Why It's Useful
EC2 instance failure	Stops or removes an EC2 instance	Shows how your app handles sudden server loss
Network issues	Slows down or cuts off network connections	Checks if your app works with poor internet
CPU overload	Makes the CPU very busy	Tests if your app can handle high demand
Storage problems	Simulates disk errors or data access issues	Checks how your app deals with data storage problems

Remember to start small, test regularly, and use the results to make your applications stronger and more reliable.

2. Before you start

2.1 Setting up your AWS account

To use AWS Fault Injection Service (AWS FIS), you need:

An active AWS account
The right permissions to use AWS FIS

2.2 Required IAM permissions

To use AWS FIS, you need specific IAM permissions:

Permission Type	Description
IAM role	Grants AWS FIS permission to run experiments
IAM policy	Allows modification of resources specified in your experiment template
Service-linked role	Named AWSServiceRoleForFIS, manages monitoring and resource selection

For more details on multi-account experiment permissions, check the AWS documentation.

2.3 Basic AWS knowledge needed

Before using AWS FIS, you should know:

Basic AWS services like EC2, ECS, EKS, RDS, and SSM
How IAM roles and permissions work

If you're new to AWS, start with the basics before using AWS FIS.

3. AWS Fault Injection Service basics

3.1 Key terms and concepts

AWS Fault Injection Service (AWS FIS) lets you test how your AWS systems handle problems. It's based on chaos engineering, which means creating controlled disruptions to see how your system responds. This helps you find weak spots and fix them.

3.2 Types of fault injections

AWS FIS offers several ways to test your system:

Fault Type	Description
Resource disruption	Stopping or terminating EC2 instances or RDS databases
API issues	Forcing failovers or slowing down API calls
Network problems	Adding delays or dropping packets in network traffic
Resource stress	Putting pressure on CPU or memory

You can target these tests at specific parts of your system, like certain EC2 instances, RDS databases, or entire Availability Zones.

3.3 Why use AWS FIS?

AWS FIS helps you:

Test your system's ability to handle problems
Find weak spots before they cause real issues
Make your applications more reliable
Work with other AWS tools like CloudWatch and IAM for better testing

4. Preparing your AWS environment

4.1 Creating test resources

Before testing with AWS FIS, set up:

Resource	Purpose
AWS account	Main access point
VPC	Network for your resources
EC2 instances or RDS databases	Targets for your tests

Follow the AWS guide to create a default VPC and EC2 instances.

4.2 Setting up IAM roles

To use AWS FIS, create an IAM role:

Role Name	Trust	Policy
AWSServiceRoleForFIS	fis.amazonaws.com	AmazonFISServiceRolePolicy

This role lets AWS FIS run tests and manage resources for you.

4.3 Creating CloudWatch alarms

Set up CloudWatch alarms to watch your resources during tests:

Metric to Monitor	Why It's Important
CPU use	Shows how busy your systems are
Memory use	Indicates if your systems have enough memory
Network traffic	Helps spot unusual activity

These alarms help you see how your system responds to the tests.

5. Making an experiment template

5.1 Opening the AWS FIS console

To create an experiment template:

Go to the AWS FIS console: https://console.aws.amazon.com/fis/
Click on Experiment templates in the menu

5.2 Setting up experiment actions

Actions are the tests AWS FIS runs on your resources. To add actions:

Click Add action
Name your action
Pick the action type
Set the action details

Action Example	Duration	Purpose
Network disruption	2 minutes	Test system response to connection loss
EC2 instance stop	5 minutes	Check recovery from sudden instance failure

5.3 Choosing targets

Targets are the resources you want to test. To set targets:

Click Edit on the auto-created target
Pick the resource type (e.g., EC2, RDS)
Choose how to select the target (e.g., by tag, by ID)

Target Type	Selection Method	Example
EC2 instance	By tag	All instances tagged "Test"
RDS database	By ID	Specific database "prod-db-1"

5.4 Adding stop conditions

Stop conditions end the test if something goes wrong. To add a stop condition:

Click Add stop condition
Pick a CloudWatch alarm you made earlier

5.5 Linking IAM roles

Link an IAM role to let AWS FIS run the test:

Choose Use an existing IAM role
Pick the IAM role you made for AWS FIS

6. Running your first test

6.1 Starting the experiment

To run your first test:

Go to the AWS FIS console
Select your experiment template
Click Start experiment
Enter a unique client token

The client token helps identify the experiment and stops accidental duplicate runs.

6.2 Watching the test progress

During the test:

Use the AWS FIS console to track progress
See which actions are happening
Check which targets are being affected

6.3 Understanding the results

After the test ends:

Step	Action
1	Look at the experiment report
2	Check which actions were done
3	See which targets were affected
4	Note any errors that happened

Use CloudWatch metrics and logs to get more details about how your system behaved during the test.

7. Common test scenarios

Here are some basic test scenarios you can use with AWS Fault Injection Service to check how well your applications handle problems:

7.1 EC2 instance failure

Test what happens when an EC2 instance stops working by turning it off or removing it. This helps you see how your application deals with sudden instance problems.

7.2 Network issues

Check how your application handles network problems like slow connections or no connection at all. This test shows if your application can work when the network isn't perfect.

7.3 CPU overload

See how your application performs when the CPU is very busy. This test helps you understand if your application can handle lots of work or many users at once.

7.4 Storage problems

Test how your application reacts when storage doesn't work right. This could be disk errors or not being able to read or write data.

Test Scenario	What It Does	Why It's Useful
EC2 instance failure	Stops or removes an EC2 instance	Shows how your app handles sudden server loss
Network issues	Slows down or cuts off network connections	Checks if your app works with poor internet
CPU overload	Makes the CPU very busy	Tests if your app can handle high demand
Storage problems	Simulates disk errors or data access issues	Checks how your app deals with data storage problems

These tests help you find weak spots in your application before they cause real problems for users.

8. Tips for effective testing

8.1 Creating useful experiments

When making tests with AWS Fault Injection Service:

Copy real-world problems
Set clear goals for your system
Guess how your system will react to issues

Test Example	What It Does	Why It's Useful
EC2 instance stops	Turns off a server	Shows how your app handles server loss
Network slows down	Makes internet connection poor	Checks if your app works with bad internet

8.2 Keeping tests safe

To run safe tests:

Use a test environment, not your live system
Have a plan to undo changes if needed
Start small and grow your tests slowly

8.3 Regular testing and updates

To get the most from AWS Fault Injection Service:

Action	Frequency	Purpose
Run tests	Every new release	Find problems early
Update test plans	When system changes	Keep tests useful
Review results	After each test	Learn and improve

9. Automating your tests

9.1 Using AWS CLI for experiments

You can use the AWS Command Line Interface (CLI) to run tests with AWS Fault Injection Service (FIS). This helps you add testing to your development process.

To create a test template with AWS CLI:

Make a JSON file with your test details
Use the aws fis create-experiment-template command
Start the test with aws fis start-experiment

Here's an example of a JSON file for a test template:

{
  "actions": {
    "terminate-instance": {
      "actionId": "terminate-instance",
      "description": "Stop an EC2 instance",
      "actionType": "aws:ec2:stopInstances",
      "targets": {
        "instances": "EC2InstancesTarget"
      },
      "parameters": {}
    }
  },
  "description": "Test EC2 instance failure",
  "roleArn": "arn:aws:iam::<ACCOUNT_ID>:role/<ROLE_NAME>",
  "stopConditions": [],
  "targets": {
    "EC2InstancesTarget": {
      "resourceType": "aws:ec2:instance",
      "selectionMode": "COUNT(1)",
      "filters": [
        {
          "path": "tags.your-key",
          "values": [
            "your-value"
          ]
        }
      ]
    }
  }
}

Replace <ACCOUNT_ID>, <ROLE_NAME>, your-key, and your-value with your own details.

9.2 Adding tests to CI/CD pipelines

You can add FIS tests to your CI/CD pipeline. This runs tests every time you update your code.

For example, use AWS CodePipeline to:

Detect code changes
Run your normal tests
Run FIS tests
Deploy if all tests pass

This helps catch problems early.

9.3 Scheduling regular tests

Running tests often helps keep your system strong. You can set up FIS to run tests on a schedule.

Scheduling Option	How to Set It Up	Benefits
Daily tests	Use AWS CloudWatch Events	Catch daily issues
Weekly tests	Use AWS CloudWatch Events	Find less common problems
After major changes	Add to your deployment process	Test new code right away

Regular testing helps you find and fix issues before they affect users.

10. Improving system reliability

10.1 Reading test results

After running a test with AWS FIS, you'll get a report showing how your system handled the fake outage. To understand these results:

Look at key numbers like error rates and response times
Check how your system used resources during the test
Note any parts that didn't work well or failed

10.2 Finding weak spots

By looking closely at your test results, you can spot areas in your system that need work. Use this table to help identify problems:

What to Look For	Why It Matters
Parts that didn't recover	These could cause long outages
Overloaded resources	May lead to slow performance or crashes
High error rates	Could mean poor user experience
Slow response times	Might frustrate users or cause timeouts

10.3 Making system improvements

Once you know where the problems are, you can fix them. Here's how to make your system stronger:

Improvement	How It Helps
Add backup systems	Keeps things running if one part fails
Spread out the workload	Stops any one part from getting too busy
Update your design	Makes your system better at handling problems
Test often	Helps you catch and fix issues early

11. Fixing common problems

11.1 When experiments fail

Sometimes, AWS FIS experiments don't work as planned. Here's how to fix common issues:

Check the AWS FIS console for error messages
Look over your experiment template for mistakes
Make sure you have the right permissions

11.2 Unexpected system reactions

Your system might act strangely during a test. To avoid this:

Action	Purpose
Watch system performance	Spot problems early
Use safety measures	Stop small issues from getting bigger
Test how your system handles failures	Find weak spots

11.3 Permission issues

Not having the right permissions is a common problem. To fix this:

Give the right permissions to IAM users and roles
Let AWS FIS run tests for you
Use service-linked roles to make managing permissions easier

Permission Type	What It Does
Identity-based policies	Control what users and roles can do
AWS FIS permissions	Allow AWS FIS to run tests
Service-linked roles	Make it easier to manage permissions

12. Wrap-up

12.1 Key points to remember

This guide showed you how to use AWS Fault Injection Service (FIS) to test your applications for outages. Here's what to keep in mind:

Key Point	Description
Start small	Begin with simple tests and slowly make them harder
Watch closely	Look at how your system acts during and after tests
Find weak spots	Use test results to see where your system needs work
Test often	Set up automatic tests to check your system regularly

12.2 Next steps

Now that you know how to use AWS FIS, it's time to put it to work:

Set up your first test using the steps in this guide
Run the test and look at the results
Fix any problems you find
Make your tests harder over time
Keep testing and fixing to make your applications stronger