ec2-start-stop-lambda-cloudwatch.yaml

# Usage:
    #   aws cloudformation --region <region> create-stack --stack-name <stack name> --template-body file://vpc-fargate.yaml
    
    # This template will:
    #   Create a cron rule in Event Bridge
    #   Also create corresponding Lambda functions and link the rules
    #   Which will automate the task of stopping and starting ec2 instances 
    #   
    #   Example:- This may help you to save some cost by automatically stopping your instances every night
    


AWSTemplateFormatVersion: '2010-09-09'
Description: Lambda function with cfn-response.
Parameters: 
  instances: 
    Default: i-0b7e303c1cb46a2fe
    Description: Instance ID's seperated by commers 
    Type: String
  Region:
    Default: ap-southeast-1 
    Description: region only 1 region supported 
    Type: String
  StopScheduled: 
    Default: cron(0 13 ? * MON-SAT *)
    Description: enter an Schedule expression example cron(0 20 ? * MON-SAT *) see https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html
    Type: String
  StartScheduled: 
    Default: cron(0 1 ? * MON-SAT *)
    Description: enter an Schedule expression example cron(0 8 ? * MON-SAT *) see https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html
    Type: String
Resources:
  StopEC2Instances:
    Type: AWS::Lambda::Function
    Properties:
      Runtime: python3.8
      Role: !GetAtt Role.Arn
      Handler: index.lambda_handler
      Timeout: 60
      Environment:
         Variables:
          instances: !Ref instances
          Region: !Ref Region
      Code:
        ZipFile: |
          import json
          import re
          import os
          import boto3
          
          def lambda_handler(event, context):
            # TODO implement
            instances_str = os.environ['instances']
            region = os.environ['Region']
            ec2 = boto3.client('ec2', region_name=region)
            instances= re.findall(r"i-[0-9a-z]{17}|i-[0-9a-z]{8}", instances_str)
            print('stopped your instances: ' + str(instances) + "in Region "+ region)
            ec2.stop_instances(InstanceIds=instances)
            
            return {
              'statusCode': 200,
              'body': json.dumps('stopped your instances: ' + str(instances))
            }
      Description: Function that stops instances
  permissionForEventsToInvokeStopEC2Instances:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !GetAtt StopEC2Instances.Arn
      Action: lambda:InvokeFunction
      Principal: events.amazonaws.com
      "SourceArn" : !GetAtt StopScheduledRule.Arn

  StartEC2Instances:
    Type: AWS::Lambda::Function
    Properties:
      Runtime: python3.8
      Role: !GetAtt Role.Arn
      Handler: index.lambda_handler
      Timeout: 60
      Environment:
         Variables:
          instances: !Ref instances
          Region: !Ref Region
      Code:
        ZipFile: |
          import json
          import re
          import os
          import boto3
          
          def lambda_handler(event, context):
            # TODO implement
            instances_str = os.environ['instances']
            region = os.environ['Region']
            ec2 = boto3.client('ec2', region_name=region)
            instances= re.findall(r"i-[0-9a-z]{17}|i-[0-9a-z]{8}", instances_str)
            print('started your instances: ' + str(instances)+ "in Region "+ region)
            ec2.start_instances(InstanceIds=instances)
            
            return {
              'statusCode': 200,
              'body': json.dumps('started your instances: ' + str(instances))
            }
      Description: Function that started instances
  permissionForEventsToInvokeStartEC2Instances:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !GetAtt StartEC2Instances.Arn
      Action: lambda:InvokeFunction
      Principal: events.amazonaws.com
      "SourceArn" : !GetAtt StartScheduledRule.Arn

  Role:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
              - lambda.amazonaws.com
            Action:
              - 'sts:AssumeRole'
      Path: /
      ManagedPolicyArns:
        - "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
      Policies:
        - PolicyName: Ec2permissions
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action:
                - "ec2:StartInstances"
                - "ec2:StopInstances"
                Resource: '*'
                

  StopScheduledRule: 
    Type: AWS::Events::Rule
    Properties: 
      Description: "ScheduledRule"
      ScheduleExpression: !Ref StopScheduled
      State: "ENABLED"
      Targets: 
        - 
          Arn: !GetAtt StopEC2Instances.Arn
          Id: "TargetFunctionV1"
  StartScheduledRule: 
    Type: AWS::Events::Rule
    Properties: 
      Description: "ScheduledRule"
      ScheduleExpression: !Ref StartScheduled
      State: "ENABLED"
      Targets: 
        - 
          Arn: !GetAtt StartEC2Instances.Arn
          Id: "TargetFunctionV1"