stack.json

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Parameters": {
    "CPUAlarmHighEvalPeriods": {
      "Type": "String",
      "Default": "1"
    },
    "CPUAlarmHighThreshold": {
      "Type": "String",
      "Default": "80"
    },
    "CPUAlarmLowThreshold": {
      "Type": "String",
      "Default": "60"
    },
    "CPUAlarmLowEvalPeriods": {
      "Type": "String",
      "Default": "5"
    },
    "AlarmPeriod": {
      "Type": "String",
      "Default": "60"
    },
    "ELBConnectionDraining": {
      "Type": "String",
      "Description": "Connection draining ensures that the load balancer completes serving all in-flight requests made to a registered instance when the instance is deregistered or becomes unhealthy",
      "Default": 30
    },
    "HealthCheckGracePeriod": {
      "Type": "String",
      "Description": "The length of time in seconds after a new EC2 instance comes into service that Auto Scaling starts checking its health.",
      "Default": 600
    },
    "ImageId": {
      "Type": "String",
      "Default": "ami-bff32ccc"
    },
    "InstanceType": {
      "Type": "String",
      "Description": "The size of the instances",
      "Default": "t2.micro"
    },
    "KeyName": {
      "Type": "String",
      "Default": "mykeypair"
    },
    "MaxSize": {
      "Type": "String",
      "Description": "The maximum number of instances",
      "Default": 2
    },
    "MinSize": {
      "Type": "String",
      "Description": "The minimum number of instances",
      "Default": 1
    },
    "PublicSubnet1Id": {
      "Type": "String",
      "Default": "subnet-"
    },
    "PublicSubnet2Id": {
      "Type": "String",
      "Default": "subnet-"
    },
    "PublicSubnet3Id": {
      "Type": "String",
      "Default": "subnet-"
    },
    "UpdateMaxBatchSize": {
      "Type": "String",
      "Description": "The maximum number of instances to be killed at one time during an ASG update.",
      "Default": 1
    },
    "UpdateMinInService": {
      "Type": "String",
      "Description": "The minimum number of instances in service during an ASG update.",
      "Default": 1
    },
    "UpdatePauseTime": {
      "Type": "String",
      "Description": "The time to wait between new instances coming online and the next batch being killed during an ASG update.",
      "Default": "PT0S"
    },
    "VpcId": {
      "Type": "String",
      "Default": "vpc-"
    }
  },
  "Resources": {
    "ComponentAutoScalingGroup": {
      "Type": "AWS::AutoScaling::AutoScalingGroup",
      "UpdatePolicy": {
        "AutoScalingRollingUpdate": {
          "MinInstancesInService": {
            "Ref": "UpdateMinInService"
          },
          "MaxBatchSize": {
            "Ref": "UpdateMaxBatchSize"
          },
          "PauseTime": {
            "Ref": "UpdatePauseTime"
          }
        }
      },
      "Properties": {
        "LoadBalancerNames": [
          {
            "Ref": "ComponentElasticLoadBalancer"
          }
        ],
        "MinSize": {
          "Ref": "MinSize"
        },
        "MaxSize": {
          "Ref": "MaxSize"
        },
        "LaunchConfigurationName": {
          "Ref": "ComponentLaunchConfiguration"
        },
        "AvailabilityZones": [
          "eu-west-1a",
          "eu-west-1b",
          "eu-west-1c"
        ],
        "HealthCheckType": "ELB",
        "HealthCheckGracePeriod": {
          "Ref": "HealthCheckGracePeriod"
        }
      }
    },
    "ComponentLaunchConfiguration": {
      "Type": "AWS::AutoScaling::LaunchConfiguration",
      "Properties": {
        "KeyName": {
          "Ref": "KeyName"
        },
        "SecurityGroups": [
          {
            "Ref": "ComponentSecurityGroup"
          }
        ],
        "InstanceType": {
          "Ref": "InstanceType"
        },
        "IamInstanceProfile": {
          "Ref": "ComponentInstanceProfile"
        },
        "ImageId": {
          "Ref": "ImageId"
        },
        "UserData": {
          "Fn::Base64": {
            "Fn::Join": [
              "",
              [
                "#cloud-config",
                "\n",
                "runcmd:\n",
                "- yum update -y\n",
                "- yum install epel-release -y\n",
                "- yum install docker -y \n",
                "- service docker start\n",
                "- docker pull davey/hello\n",
                "- docker run -d -p 8080:9292 davey/hello\n"
              ]
            ]
          }
        }
      }
    },
    "ComponentScaleUpPolicy": {
      "Type": "AWS::AutoScaling::ScalingPolicy",
      "Properties": {
        "AutoScalingGroupName": {
          "Ref": "ComponentAutoScalingGroup"
        },
        "AdjustmentType": "ChangeInCapacity",
        "Cooldown": 240,
        "ScalingAdjustment": 1
      }
    },
    "ComponentScaleDownPolicy": {
      "Type": "AWS::AutoScaling::ScalingPolicy",
      "Properties": {
        "AutoScalingGroupName": {
          "Ref": "ComponentAutoScalingGroup"
        },
        "AdjustmentType": "ChangeInCapacity",
        "Cooldown": 60,
        "ScalingAdjustment": -1
      }
    },
    "CPUAlarmHigh": {
      "Type": "AWS::CloudWatch::Alarm",
      "Properties": {
        "AlarmDescription": "Scale-up if CPU > 80% for 1 minutes",
        "Threshold": {
          "Ref": "CPUAlarmHighThreshold"
        },
        "AlarmActions": [
          {
            "Ref": "ComponentScaleUpPolicy"
          }
        ],
        "ComparisonOperator": "GreaterThanThreshold",
        "EvaluationPeriods": {
          "Ref": "CPUAlarmHighEvalPeriods"
        },
        "MetricName": "CPUUtilization",
        "Namespace": "AWS/EC2",
        "Statistic": "Average",
        "Period": {
          "Ref": "AlarmPeriod"
        },
        "Dimensions": [
          {
            "Name": "AutoScalingGroupName",
            "Value": {
              "Ref": "ComponentAutoScalingGroup"
            }
          }
        ]
      }
    },
    "CPUAlarmLow": {
      "Type": "AWS::CloudWatch::Alarm",
      "Properties": {
        "AlarmDescription": "Scale-down if CPU < 60% for 5 minutes",
        "Threshold": {
          "Ref": "CPUAlarmLowThreshold"
        },
        "AlarmActions": [
          {
            "Ref": "ComponentScaleDownPolicy"
          }
        ],
        "ComparisonOperator": "LessThanThreshold",
        "EvaluationPeriods": {
          "Ref": "CPUAlarmLowEvalPeriods"
        },
        "MetricName": "CPUUtilization",
        "Namespace": "AWS/EC2",
        "Statistic": "Average",
        "Period": {
          "Ref": "AlarmPeriod"
        },
        "Dimensions": [
          {
            "Name": "AutoScalingGroupName",
            "Value": {
              "Ref": "ComponentAutoScalingGroup"
            }
          }
        ]
      }
    },
    "LoadBalancerSecurityGroup": {
      "Type": "AWS::EC2::SecurityGroup",
      "Properties": {
        "SecurityGroupIngress": [
          {
            "ToPort": 8080,
            "IpProtocol": "tcp",
            "FromPort": 8080,
            "CidrIp": "0.0.0.0/0"
          }
        ],
        "VpcId": {
          "Ref": "VpcId"
        },
        "GroupDescription": "An ELB group allowing access only to from the corresponding component"
      }
    },
    "ComponentSecurityGroup": {
      "Type": "AWS::EC2::SecurityGroup",
      "Properties": {
        "SecurityGroupIngress": [
          {
            "FromPort": 8080,
            "ToPort": 8080,
            "IpProtocol": "tcp",
            "SourceSecurityGroupId": {
              "Ref": "LoadBalancerSecurityGroup"
            }
          }
        ],
        "VpcId": {
          "Ref": "VpcId"
        },
        "GroupDescription": "A component security group allowing access only from the corresponding ELB"
      }
    },
    "ELBRule": {
      "Type": "AWS::ElasticLoadBalancingV2::ListenerRule",
      "Properties": {
        "Actions": [
          {
            "TargetGroupArn": {
              "Ref": "ELBTargetGroup"
            },
            "Type": "forward"
          }
        ],
        "Conditions": [
          {
            "Field": "path-pattern"
          }
        ],
        "ListenerArn": {
          "Ref": "ELBListen"
        },
        "Priority": 1
      }
    },
    "ELBListen": {
      "Type": "AWS::ElasticLoadBalancingV2::Listener",
      "Properties": {
        "DefaultActions": [
          {
            "TargetGroupArn": {
              "Ref": "ELBTargetGroup"
            },
            "Type": "forward"
          }
        ],
        "LoadBalancerArn": {
          "Ref": "ComponentElasticLoadBalancer"
        },
        "Port": 8080,
        "Protocol": "HTTP"
      }
    },
    "ELBTargetGroup": {
      "Type": "AWS::ElasticLoadBalancingV2::TargetGroup",
      "Properties": {
        "HealthCheckIntervalSeconds": "15",
        "HealthCheckPath": "/status",
        "HealthCheckPort": "8080",
        "HealthCheckProtocol": "HTTP",
        "HealthCheckTimeoutSeconds": 300,
        "HealthyThresholdCount": 3,
        "Port": 8080,
        "Protocol": "HTTP",
        "Targets": [
          {
            "Ref": "ComponentAutoScalingGroup"
          }
        ],
        "UnhealthyThresholdCount": 5,
        "VpcId": {
          "Ref": "VpcId"
        }
      }
    },
    "ComponentElasticLoadBalancer": {
      "Type": "AWS::ElasticLoadBalancingV2::LoadBalancer",
      "Properties": {
        "Name": "ALB",
        "Subnets": [
          {
            "Ref": "PublicSubnet1Id"
          },
          {
            "Ref": "PublicSubnet2Id"
          },
          {
            "Ref": "PublicSubnet3Id"
          }
        ],
        "SecurityGroups": [
          {
            "Ref": "LoadBalancerSecurityGroup"
          }
        ]
      }
    },
    "ComponentInstanceProfile": {
      "Type": "AWS::IAM::InstanceProfile",
      "Properties": {
        "Path": "/",
        "Roles": [
          {
            "Ref": "DefaultRole"
          }
        ]
      }
    },
    "EC2ComponentPolicy": {
      "Type": "AWS::IAM::Policy",
      "Properties": {
        "PolicyDocument": {
          "Statement": [
            {
              "Action": [
                "cloudwatch:*"
              ],
              "Resource": [
                "*"
              ],
              "Effect": "Allow"
            },
            {
              "Action": [
                "cloudformation:Describe*"
              ],
              "Resource": [
                "*"
              ],
              "Effect": "Allow"
            },
            {
              "Action": [
                "ec2:Describe*"
              ],
              "Resource": [
                "*"
              ],
              "Effect": "Allow"
            }
          ]
        },
        "PolicyName": "EC2ComponentPolicy",
        "Roles": [
          {
            "Ref": "DefaultRole"
          }
        ]
      }
    },
    "DefaultRole": {
      "Type": "AWS::IAM::Role",
      "Properties": {
        "Path": "/",
        "AssumeRolePolicyDocument": {
          "Statement": [
            {
              "Action": [
                "sts:AssumeRole"
              ],
              "Effect": "Allow",
              "Principal": {
                "Service": [
                  "ec2.amazonaws.com"
                ]
              }
            }
          ]
        }
      }
    }
  }
}