3 instances behind load balancer.

Author: MartinRixham

cloudformation.json

@@ -6,10 +6,6 @@
       "Type": "String",
       "Default": "t3.micro"
     },
-    "DesiredCapacity": {
-      "Type": "Number",
-      "Default": 2
-    },
     "ECSAMI": {
       "Type": "AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>",
       "Default": "/aws/service/ecs/optimized-ami/amazon-linux-2/recommended/image_id"
@@ -52,6 +48,15 @@
         "MapPublicIpOnLaunch": true
       }
     },
+    "PublicSubnet3": {
+      "Type": "AWS::EC2::Subnet",
+      "Properties": {
+        "VpcId": { "Ref": "VPC" },
+        "CidrBlock": "10.0.3.0/24",
+        "AvailabilityZone": { "Fn::Select": [ 2, { "Fn::GetAZs": "" } ] },
+        "MapPublicIpOnLaunch": true
+      }
+    },
     "PublicRouteTable": {
       "Type": "AWS::EC2::RouteTable",
       "Properties": {
@@ -81,6 +86,13 @@
         "RouteTableId": { "Ref": "PublicRouteTable" }
       }
     },
+    "SubnetRouteTableAssociation3": {
+      "Type": "AWS::EC2::SubnetRouteTableAssociation",
+      "Properties": {
+        "SubnetId": { "Ref": "PublicSubnet3" },
+        "RouteTableId": { "Ref": "PublicRouteTable" }
+      }
+    },
     "InstanceSecurityGroup": {
       "Type": "AWS::EC2::SecurityGroup",
       "Properties": {
@@ -102,6 +114,24 @@
         ]
       }
     },
+    "ALBSecurityGroup": {
+      "Type": "AWS::EC2::SecurityGroup",
+      "Properties": {
+        "VpcId": { "Ref": "VPC" },
+        "GroupDescription": "Allow inbound HTTP from anywhere",
+        "SecurityGroupIngress": [
+          {
+            "IpProtocol": "tcp",
+            "FromPort": 80,
+            "ToPort": 80,
+            "CidrIp": "0.0.0.0/0"
+          }
+        ],
+        "SecurityGroupEgress": [
+          { "IpProtocol": "-1", "CidrIp": "0.0.0.0/0" }
+        ]
+      }
+    },
     "InstanceRole": {
       "Type": "AWS::IAM::Role",
       "Properties": {
@@ -161,17 +191,51 @@
         }
       }
     },
+    "ApplicationLoadBalancer": {
+      "Type": "AWS::ElasticLoadBalancingV2::LoadBalancer",
+      "Properties": {
+        "Name": "ClusterALB",
+        "Scheme": "internet-facing",
+        "Subnets": [{ "Ref": "PublicSubnet1" }, { "Ref": "PublicSubnet2" }, { "Ref": "PublicSubnet3" }],
+        "SecurityGroups": [{ "Ref": "ALBSecurityGroup" }]
+      }
+    },
+    "ALBTargetGroup": {
+      "Type": "AWS::ElasticLoadBalancingV2::TargetGroup",
+      "Properties": {
+        "VpcId": { "Ref": "VPC" },
+        "Port": 80,
+        "Protocol": "HTTP",
+        "TargetType": "instance",
+        "HealthCheckPath": "/"
+      }
+    },
+    "ALBListener": {
+      "Type": "AWS::ElasticLoadBalancingV2::Listener",
+      "Properties": {
+        "LoadBalancerArn": { "Ref": "ApplicationLoadBalancer" },
+        "Port": 80,
+        "Protocol": "HTTP",
+        "DefaultActions": [
+          {
+            "Type": "forward",
+            "TargetGroupArn": { "Ref": "ALBTargetGroup" }
+          }
+        ]
+      }
+    },
     "AutoScalingGroup": {
       "Type": "AWS::AutoScaling::AutoScalingGroup",
       "Properties": {
-        "VPCZoneIdentifier": [ { "Ref": "PublicSubnet1" }, { "Ref": "PublicSubnet2" } ],
+        "VPCZoneIdentifier": [ { "Ref": "PublicSubnet1" }, { "Ref": "PublicSubnet2" }, { "Ref": "PublicSubnet3" } ],
         "LaunchTemplate": {
           "LaunchTemplateId": { "Ref": "LaunchTemplate" },
           "Version": { "Fn::GetAtt": [ "LaunchTemplate", "LatestVersionNumber" ] }
         },
-        "DesiredCapacity": { "Ref": "DesiredCapacity" },
+        "DesiredCapacity": 3,
         "MinSize": "1",
-        "MaxSize": "4"
+        "MaxSize": "4",
+        "TargetGroupARNs":[{ "Ref":"ALBTargetGroup" } ]
       }
     }
   }