spot-interruption-deregist-alb.yaml

Description: Deregister-targets (alb) when spot instance interruption
# spot-interruption-deregist-alb.yaml

Resources:
  EventRule:
    Type: AWS::Events::Rule
    Properties:
      Description: EventRule
      EventPattern:
        detail-type:
        - EC2 Spot Instance Interruption Warning
        source:
        - aws.ec2
      State: ENABLED
      Targets:
      - Arn: !Ref 'SnsTopic'
        Id: EventRuleAdminswich
      Targets:
      - Arn: !GetAtt 'LambdaFunction.Arn'
        Id: LambdaFunction

  LambdaPermission:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !Ref 'LambdaFunction'
      Action: lambda:InvokeFunction
      Principal: events.amazonaws.com
      SourceArn: !GetAtt 'EventRule.Arn'

  LogGroupLambda:
    Type: AWS::Logs::LogGroup
    Properties:
      LogGroupName: !Sub '/aws/lambda/${LambdaFunction}'
      RetentionInDays: 14

  LambdaRole:
    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:CreateLogGroup
                  - logs:CreateLogStream
                  - logs:PutLogEvents
                Resource: '*'
              - Effect: Allow
                Action:
                  - elasticloadbalancing:DescribeLoadBalancers
                  - elasticloadbalancing:DescribeTags
                  - elasticloadbalancing:DescribeTargetHealth
                  - elasticloadbalancing:DescribeTargetGroups
                  - elasticloadbalancing:DeregisterTargets
                Resource: '*'
              - Effect: Allow
                Action:
                  - ec2:DescribeInstances
                  - ec2:DescribeTags
                  - autoscaling:DescribeAutoScalingGroups
                Resource: '*'

  LambdaFunction:
    Type: AWS::Lambda::Function
    Properties:
      Handler: index.lambda_handler
      Role: !GetAtt 'LambdaRole.Arn'
      Code:
        ZipFile: !Sub |
          import boto3
          
          def lambda_handler(event, context):
            instance_id = event['detail']['instance-id']

            asg_name = get_asg_name(instance_id)
            if len(asg_name) > 0:
              targetgroup_arns = get_asg_targetgrouparn(asg_name)
              for targetgroup_arn in targetgroup_arns:
                target_ids = describe_target_health(targetgroup_arn,instance_id)
                if len(target_ids) > 0:
                  deregister_targets(targetgroup_arn,target_ids)

          def get_asg_name(instance_id):
            client = boto3.client('ec2')
            response = client.describe_instances(Filters=[{'Name':'instance-id', 'Values':[instance_id]}])
            StateName = response['Reservations'][0]['Instances'][0]['State']['Name']

            asg_name = ''
            if StateName == 'running':
              for tag in response['Reservations'][0]['Instances'][0]['Tags']:
                if tag['Key'] == 'aws:autoscaling:groupName':
                  asg_name = tag['Value']

            LaunchTime = response['Reservations'][0]['Instances'][0]['LaunchTime']
            AvailabilityZone = response['Reservations'][0]['Instances'][0]['Placement']['AvailabilityZone']
            InstanceType = response['Reservations'][0]['Instances'][0]['InstanceType']
            print('instance-id: ' + str(instance_id))
            print('InstanceType: ' + str(InstanceType))
            print('AvailabilityZone: ' + str(AvailabilityZone))
            print('LaunchTime: ' + str(LaunchTime))

            print('asg_name: ' + asg_name)
            return asg_name

          def get_asg_targetgrouparn(asg_name):
            client = boto3.client('autoscaling')
            response = client.describe_auto_scaling_groups(AutoScalingGroupNames=[asg_name])
            targetgroup_arns = response['AutoScalingGroups'][0]['TargetGroupARNs']
            print('targetgroup_arns:' + str(targetgroup_arns))
            return targetgroup_arns

          def describe_target_health(targetgroup_arn,instance_id):
            client = boto3.client('elbv2')
            response = client.describe_target_health(
              TargetGroupArn = targetgroup_arn
            )
            target_ids = []
            for a in response['TargetHealthDescriptions']:
              if a['Target']['Id'] == instance_id:
                if a['TargetHealth']['State'] == 'healthy':
                  target_ids.append(a['Target'])
            print('target_ids:' + str(target_ids))
            return target_ids

          def deregister_targets(targetgroup_arn,target_ids):
            client = boto3.client('elbv2')
            response = client.deregister_targets(
              TargetGroupArn = targetgroup_arn,
              Targets = target_ids,
            )

      Runtime: python3.6
      MemorySize: 128
      Timeout: 300
      Description: Deregister-targets (alb) when spot instance interruption
      Tags:
        - Key: CloudformationArn
          Value: !Ref 'AWS::StackId'