Creating an ALB Target Group in CloudFormation - amazon-web-services

Question

I'm trying to create an Application Load Balancer in CloudFormation, with a target group that forwards traffic to EC2 instances. Here is the relevant snippet, where ELBSubnets, ECSCluster, taskdefinition, and VpcId are passed in as parameters:
"EcsElasticLoadBalancer" : {
"Type" : "AWS::ElasticLoadBalancingV2::LoadBalancer",
"Properties" : {
"Subnets" : { "Ref" : "ELBSubnets" },
"SecurityGroups": [
{ "Ref": "ELBAccessSecurityGroup" }
]
}
},
"LoadBalancerListener": {
"Type": "AWS::ElasticLoadBalancingV2::Listener",
"Properties": {
"DefaultActions": [{
"Type": "forward",
"TargetGroupArn": { "Ref": "TargetGroup" }
}],
"LoadBalancerArn": { "Ref": "EcsElasticLoadBalancer" },
"Port": 80,
"Protocol": "HTTP"
}
},
"TargetGroup": {
"Type": "AWS::ElasticLoadBalancingV2::TargetGroup",
"Properties": {
"Name": { "Fn::Join": [ "-", [ { "Ref": "AWS::StackName" }, "TargetGroup" ] ] },
"Port": 80,
"Protocol": "HTTP",
"VpcId": { "Ref": "VpcId" }
},
"DependsOn": [ "EcsElasticLoadBalancer" ]
},
"service": {
"Type": "AWS::ECS::Service",
"Properties" : {
"Cluster": { "Ref": "ECSCluster" },
"DesiredCount": "1",
"LoadBalancers": [
{
"ContainerName": "main-app",
"ContainerPort": 3000,
"TargetGroupArn": { "Ref": "TargetGroup" }
}
],
"Role" : {"Ref":"ECSServiceRole"},
"TaskDefinition" : {"Ref":"taskdefinition"}
}
},
"ECSServiceRole": {
"Type": "AWS::IAM::Role",
"Properties": {
"AssumeRolePolicyDocument": {
"Statement": [
{
"Effect": "Allow",
"Principal": {
"Service": [
"ecs.amazonaws.com"
]
},
"Action": [
"sts:AssumeRole"
]
}
]
},
"Path": "/",
"Policies": [
{
"PolicyName": "ecs-service",
"PolicyDocument": {
"Statement": [
{
"Effect": "Allow",
"Action": [
"elasticloadbalancing:Describe*",
"elasticloadbalancing:DeregisterInstancesFromLoadBalancer",
"elasticloadbalancing:RegisterInstancesWithLoadBalancer",
"ec2:Describe*",
"ec2:AuthorizeSecurityGroupIngress"
],
"Resource": "*"
}
]
}
}
]
}
}
I get the following error when creating the service:
The target group with targetGroupArn arn:aws:elasticloadbalancing:us-east-1:xxxxxxxx:targetgroup/AlbServiceStack-TargetGroup/6ba9c037c26cdb36 does not have an associated load balancer.
What am I missing? In the documentation there doesn't seem to be a way to specify a load balancer for the target group.

Answer 1

Got it working - the problem was twofold:
The following lines were missing from the Role PolicyDocument:
"elasticloadbalancing:DeregisterTargets"
"elasticloadbalancing:RegisterTargets"
The service needed "DependsOn": [ "LoadBalancerListener" ] as an additional attribute.
Updated template looks like this:
"EcsElasticLoadBalancer" : {
"Type" : "AWS::ElasticLoadBalancingV2::LoadBalancer",
"Properties" : {
"Subnets" : { "Ref" : "ELBSubnets" },
"SecurityGroups": [
{ "Ref": "ELBAccessSecurityGroup" }
]
}
},
"LoadBalancerListener": {
"Type": "AWS::ElasticLoadBalancingV2::Listener",
"Properties": {
"DefaultActions": [{
"Type": "forward",
"TargetGroupArn": { "Ref": "TargetGroup" }
}],
"LoadBalancerArn": { "Ref": "EcsElasticLoadBalancer" },
"Port": 80,
"Protocol": "HTTP"
}
},
"TargetGroup": {
"Type": "AWS::ElasticLoadBalancingV2::TargetGroup",
"Properties": {
"Name": { "Fn::Join": [ "-", [ { "Ref": "AWS::StackName" }, "TargetGroup" ] ] },
"Port": 80,
"Protocol": "HTTP",
"VpcId": { "Ref": "VpcId" }
},
"DependsOn": [ "EcsElasticLoadBalancer" ]
},
"service": {
"Type": "AWS::ECS::Service",
"DependsOn": [ "LoadBalancerListener" ],
"Properties" : {
"Cluster": { "Ref": "ECSCluster" },
"DesiredCount": "1",
"LoadBalancers": [
{
"ContainerName": "main-app",
"ContainerPort": 3000,
"TargetGroupArn": { "Ref": "TargetGroup" }
}
],
"Role" : {"Ref":"ECSServiceRole"},
"TaskDefinition" : {"Ref":"taskdefinition"}
}
},
"ECSServiceRole": {
"Type": "AWS::IAM::Role",
"Properties": {
"AssumeRolePolicyDocument": {
"Statement": [
{
"Effect": "Allow",
"Principal": {
"Service": [
"ecs.amazonaws.com"
]
},
"Action": [
"sts:AssumeRole"
]
}
]
},
"Path": "/",
"Policies": [
{
"PolicyName": "ecs-service",
"PolicyDocument": {
"Statement": [
{
"Effect": "Allow",
"Action": [
"elasticloadbalancing:Describe*",
"elasticloadbalancing:DeregisterInstancesFromLoadBalancer",
"elasticloadbalancing:RegisterInstancesWithLoadBalancer",
"ec2:Describe*",
"ec2:AuthorizeSecurityGroupIngress",
"elasticloadbalancing:DeregisterTargets",
"elasticloadbalancing:RegisterTargets"
],
"Resource": "*"
}
]
}
}
]
}
}