AWS Lambda EC2 Stop-Start

A simple AWS Lambda function for stopping/starting instances based on tags (for demo purpose).

Function behavior

This solution use two lambda functions (one for starting, one for stopping). These functions will targeting the instances based on the tags applied on them.

There is two ways to gives to Lambda functions the tags to seek.

Targeting instances with Lambda environment variables

You can tell to the functions which tags to use by specifying it in the environment variables of each function.

You can set these environment variables directly in the Terraform template. Only one thing is mandatory: you must use the syntax bellow.

• Target<DIGIT> as key
• <TAG>:<VALUE> as value

Here is few examples:

• "Target1" as key and "Project:MyProject" as value
• "Target2" as key and "Environment:Production" as value
• and so on

With this example, functions will target instances with tag "Project" (with value MyProject) AND tag "Environment" (with value "Production") applied on them.

Targeting instances with Lambda event

You can tell to the functions which tags to use by giving them into an event. If so, the target tags declared into this event will have a more precedence than target tags passed through environment variables. That mean environment variables will be ignored.

Here is an example:

{
  "Target1": "Project:MyProject",
  "Target2": "Environment:Production"
}

With this example, functions will target instances with tag "Project" (with value MyProject) AND tag "Environment" (with value "Production") applied on them.

Note about Auto Scaling Groups

If one instance is part of an ASG (Auto Scaling Group), this ASG will be suspended while the instance is stopped to avoid instance deletion.

Usage

Deployment

You can use the Terraform called "lambda-deployment.tf" for doing that. By default, the functions will be named (but these names can be changed):

• ${var.APP_NAME}-${var.ENV_NAME}-start
• ${var.APP_NAME}-${var.ENV_NAME}-stop

But you can modify that directly in the template or with tfvars files.

How to triggered the lambda function ?

These functions can be triggered exactly like all other lambda function. By CLI, for instance :

• aws lambda invoke --function-name <FUNCTION_NAME> --region eu-west-1 output.txt
• aws lambda invoke --function-name <FUNCTION_NAME> --region eu-west-1 output.txt

Note that you will need to install on your PC the AWS CLI (and Python as dependency) and set your AWS credentials correctly.

But many other ways to call these functions are possible:

• by CloudWatch Event/Rule
• by API Gateway
• by SNS/SQS
• ...

How to install a "START/STOP" like button ?

Let's assume that you want to do that on a Windows machine (but it's nearly the same thing on a Linux machine).

Here is the steps:

1. Install Python on the related machine (you may have admin rights to do that)
2. Install the AWS CLI by launching this command in cmd.exe : pip install awscli
3. Still in cmd.exe, add your credentials by typing: aws configure

Now you can create two files, like START.bat and STOP.bat and put inside the corresponding command.

aws lambda invoke --function-name <FUNCTION_NAME> --region output.txt

On the AWS IAM side, the user you will use to launch these functions must have the rights to do that. You can achieve that with this IAM policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmt1536831409355",
      "Action": [
        "lambda:InvokeFunction"
      ],
      "Effect": "Allow",
      "Resource": "*"
    }
  ]
}

IMPORTANT : the previous example, authorize the user to invoke all the functions. You can change that and put the related ARN in the resource section of the document.

License

This project is released under MIT license.