In this tutorial, we will develop a self destructing cloudformation stack.
The stack can ben named harakiri since it will delete not only the resources created but also itself after a specified duration.
The stack is best suited for timely
For example, a potential customer wants to try your SaaS before paid subscription and you do not want to be charged for the unused resources.
It would be better have a basic knowledge about CloudFormation.
AWS Cloud Formation is a infrastructure as a code that creates, updates and deletes resources with JSON or YAML configuration files.
Defining Stack
AWS Cloud Formation template has five sections:
- Mapping
- Parameters
- Conditions
- Resources
- Outputs
In the resources section we define the AWS Resources that will be created. I will keep it simple and focus on only the resources section.
Trivial Section
AWSTemplateFormatVersion: "2010-09-09"
Mappings:
RegionMap:
us-east-1:
AMI: "ami-0ff8a91507f77f867"
Parameters: {}
Conditions: {}
There is nothing fancy here. Although we are not going to create and EC2 instance, at least one region (the region you will be creating the stack)
is required. Also AMI (Amazon Machine Image) can be wrong. Just skip it.
IAM Role for The Lambda
We use lambda for triggering the stack delete process. This IAM role must be priviled to delete all resources created with stack.
You would like give full privilege this role but be safe by giving fine grained privilege by giving privilege to this role for only the resources
created with stack.
We gave privilege to this role:
- Deleting all cloud formation stacks
- Deleting all IAM roles. (This role will able to delete itself)
- Deleting all lambda functions
- Deleting all cloudwatch events and rules
Resources:
LambdaExecutionRole:
Type: AWS::IAM::Role
Properties:
AssumeRolePolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Principal:
Service:
- lambda.amazonaws.com
Action:
- sts:AssumeRole
Path: "/"
Policies:
- PolicyName: root
PolicyDocument:
Version: '2012-10-17'
Statement:
- Effect: Allow
Action:
- logs:*
Resource: arn:aws:logs:*:*:*
- Effect: Allow
Action:
- cloudformation:DeleteStack
Resource: "*"
- Effect: Allow
Action:
- iam:DeleteRolePolicy
- iam:DeleteRole
Resource: "*"
- Effect: Allow
Action:
- lambda:DeleteFunction
Resource: "*"
- Effect: Allow
Action:
- events:RemoveTargets
Resource: "*"
- Effect: Allow
Action:
- events:DeleteRule
Resource: "*"
- Effect: Allow
Action:
- lambda:RemovePermission
Resource: "*"
Lambda Function
This lambda function will trigger the stack delete process.
I prefer giving permission to lambda role fine grained which means as you added any different kind of resources, you must add delete permission for this resource to LambdaExecutionRole also. If the permissions of lambda roles lacks and, stack delete process can not completed and you continue to be charged for remainig resources.
- How does this lambda function trigger?
- Cloud Watch Rules.
We will define a cloud watch timer later. The cloud watch timer will trigger every X times but since the lambda function
will delete all resources created with stack, probably there would be no second execution.
Boto is a Python package that provides interfaces to Amazon Web Services.
import boto3
client = boto3.client('cloudformation')
def handler(event, context):
return client.delete_stack(StackName=event.StackName)
Source code of lambda function is simple. It requires a simple JSON object with a StackName property which is the name of the
Cloud Formation stack.
HarakiriLambda:
Type: AWS::Lambda::Function
Properties:
Handler: index.handler
Role: !GetAtt LambdaExecutionRole.Arn
Code:
ZipFile: |
import boto3
client = boto3.client('cloudformation')
def handler(event, context):
return client.delete_stack(
StackName=event.StackName
)
Runtime: python3.6
PermissionForEventsToInvokeLambda:
Type: AWS::Lambda::Permission
Properties:
FunctionName:
Ref: "HarakiriLambda"
Action: "lambda:InvokeFunction"
Principal: "events.amazonaws.com"
SourceArn:
Fn::GetAtt:
- "HarakiriRule"
- "Arn"
CloudWatch Timer (Rule)
We will define a cloud watch cron rule that will be executed every thirty minutes but we expect it does not executed twice about five or ten minutes after the first execution, all resources including this rule will be deleted.
We prepare a simple JSON object at line 107, for the lambda by substituting the stack name.
HarakiriRule:
Type: AWS::Events::Rule
Properties:
Description: "ScheduledRule"
ScheduleExpression: "cron(0/30 * * * ? *)"
State: "ENABLED"
Targets:
-
Arn:
Fn::GetAtt:
- "HarakiriLambda"
- "Arn"
Id: "HarakiriLambdaV1"
Input: !Sub
- "{\"StackName\": \"${Stack}\"}"
- { Stack: !Ref "AWS::StackName" }
Final
- Go to AWS Cloud Formation Console: console.aws.amazon.com/cloudformation
- Download the full template from template.yml and change the 30 minutes section to 2-3 minutes.
- Click "Create Stack" button and upload the template.
- Hit the "Next" button and give a name to your stack.
- Watch the events tabs at the bottom.
You will see the stack create process, just after 2-3 minutes, "stack delete in progress" event will appear.
From the CLI you can create the stack by typing:
aws cloudformation deploy \
--stack-name myteststack \
--capabilities CAPABILITY_IAM \
--template-file template.yml
Conclusion
I hope you enjoyed and learnt a lot.
Happy coding.
Top comments (1)
Hello friend
the github link does not found.
Could you please provide us with the full templete.
Regards