Ec2 and Elastic load Balancer - amazon-web-services

Question

Please consider this scenario:
I want to deploy a CloudFormation stack with the basic required resources for an Elastic Load Balancer to route traffic to the EC2.
I have stripped bellow template from a template that has a VPC, InternetGateway, VPCGatewayAttachment, RouteTable, Route, SubnetRouteTableAssociation, attached to it.
I did so because I thought AWS will provision a default VPC for me.
Mappings:
NetworkToSubnet:
"10.0.0.0":
PubSubnetZoneA: "10.0.10.0/24"
PrivSubnetZoneA: "10.0.20.0/24"
PubSubnetZoneB: "10.0.30.0/24"
PrivSubnetZoneB: "10.0.40.0/24"
Resources:
# Internet accessable subnet in the first availability zone
PubSubnetZoneA:
Type: 'AWS::EC2::Subnet'
Properties:
AvailabilityZone:
Fn::Select:
- '0'
- Fn::GetAZs:
Ref: 'AWS::Region'
CidrBlock:
Fn::FindInMap:
- NetworkToSubnet
- '10.0.0.0'
- PubSubnetZoneA
MapPublicIpOnLaunch: 'True'
Tags:
- Key: 'Name'
Value:
'Fn::Join': [ ':', [ 'Public', 'Zone A', !Ref 'AWS::StackName' ] ]
# Non-internet accessable subnet in the first availability zone
PrivSubnetZoneA:
Type: 'AWS::EC2::Subnet'
Properties:
AvailabilityZone:
Fn::Select:
- '0'
- Fn::GetAZs:
Ref: 'AWS::Region'
CidrBlock:
Fn::FindInMap:
- NetworkToSubnet
- '10.0.0.0'
- PrivSubnetZoneA
MapPublicIpOnLaunch: 'False'
Tags:
- Key: 'Name'
Value:
'Fn::Join': [ ':', [ 'Private', 'Zone A', !Ref 'AWS::StackName' ] ]
# Internet accessable subnet in the second availability zone
PubSubnetZoneB:
Type: 'AWS::EC2::Subnet'
Properties:
AvailabilityZone:
Fn::Select:
- '1'
- Fn::GetAZs:
Ref: 'AWS::Region'
CidrBlock:
Fn::FindInMap:
- NetworkToSubnet
- '10.0.0.0'
- PubSubnetZoneB
MapPublicIpOnLaunch: 'True'
Tags:
- Key: 'Name'
Value:
'Fn::Join': [ ':', [ 'Public', 'Zone B', !Ref 'AWS::StackName' ] ]
# Non-internet accessable subnet in the second availability zone
PrivSubnetZoneB:
Type: 'AWS::EC2::Subnet'
Properties:
AvailabilityZone:
Fn::Select:
- '1'
- Fn::GetAZs:
Ref: 'AWS::Region'
CidrBlock:
Fn::FindInMap:
- NetworkToSubnet
- '10.0.0.0'
- PrivSubnetZoneB
MapPublicIpOnLaunch: 'False'
Tags:
- Key: 'Name'
Value:
'Fn::Join': [ ':', [ 'Private', 'Zone B', !Ref 'AWS::StackName' ] ]
# EC2 Security Group Allowing Port 22 and 80 from anywhere
EC2SecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: 'SSH and Port 80'
SecurityGroupIngress:
- IpProtocol: tcp
FromPort: 22
ToPort: 22
CidrIp: 0.0.0.0/0
- IpProtocol: tcp
FromPort: 80
ToPort: 80
SourceSecurityGroupId:
Ref: ELBSecurityGroup
# ELB Security Group allowing Port 80 from anywhere
ELBSecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: 'SSH and Port 80'
SecurityGroupIngress:
- IpProtocol: tcp
FromPort: 80
ToPort: 80
CidrIp: 0.0.0.0/0
# Linux Instance with Apache running on Port 80
AmazonLinuxInstance:
Type: AWS::EC2::Instance
Properties:
ImageId: ami-0ffd774e02309201f
InstanceInitiatedShutdownBehavior: stop
InstanceType: t2.nano
Monitoring: 'true'
NetworkInterfaces:
- AssociatePublicIpAddress: 'true'
DeviceIndex: '0'
GroupSet:
- !Ref EC2SecurityGroup
Tenancy: default
UserData:
Fn::Base64: !Sub |
#!/bin/bash -xe
cd /tmp
yum update -y
yum install -y httpd24
echo "Healthy" > /var/www/html/index.html
service httpd start
/opt/aws/bin/cfn-signal \
-e $? \
--stack ${AWS::StackName} \
--resource AmazonLinuxInstance \
--region ${AWS::Region}
# Target Group
EC2TargetGroup:
Type: AWS::ElasticLoadBalancingV2::TargetGroup
Properties:
HealthCheckIntervalSeconds: 30
HealthCheckProtocol: HTTP
HealthCheckTimeoutSeconds: 15
HealthyThresholdCount: 5
Matcher:
HttpCode: '200'
Name: EC2TargetGroup
Port: 80
Protocol: HTTP
TargetGroupAttributes:
- Key: deregistration_delay.timeout_seconds
Value: '20'
Targets:
- Id:
Ref: AmazonLinuxInstance
Port: 80
UnhealthyThresholdCount: 3
Tags:
- Key: Name
Value: EC2TargetGroup
- Key: Port
Value: 80
#ELB (ALB)
ALBListener:
Type: AWS::ElasticLoadBalancingV2::Listener
Properties:
DefaultActions:
- Type: forward
TargetGroupArn:
Ref: EC2TargetGroup
LoadBalancerArn:
Ref: ApplicationLoadBalancer
Port: 80
Protocol: HTTP
ApplicationLoadBalancer:
Type: AWS::ElasticLoadBalancingV2::LoadBalancer
Properties:
Scheme: internet-facing # or internal
Outputs:
ALBHostName:
Description: 'Application Load Balancer Hostname'
Value:
!GetAtt ApplicationLoadBalancer.DNSName
EC2Instance:
Description: 'EC2 Instance'
Value:
Ref: AmazonLinuxInstance
EC2TargetGroup:
Description: 'EC2 Target Group'
Value:
Ref: EC2TargetGroup
ApplicationLoadBalancer:
Description: 'Application Load Balancer'
Value:
Ref: ApplicationLoadBalancer
When provisioning the stack provided I get the following errors:
The following resource(s) failed to create: [PubSubnetZoneB, PrivSubnetZoneA,
PrivSubnetZoneB, ApplicationLoadBalancer, ELBSecurityGroup, PubSubnetZoneA]. Rollback
requested by user.
At least two subnets in two different Availability Zones must be specified (Service:
AmazonElasticLoadBalancing; Status Code: 400; Error Code: ValidationError; Request ID: 000-
0000-0000-0000-0000; Proxy: null)
What are the minimum required resources for an ELB to have, so it can direct traffic to an EC2?

Answer 1

The error is saying At least two subnets in two different Availability Zones must be specified.
From AWS::ElasticLoadBalancingV2::LoadBalancer - AWS CloudFormation:
Subnets
The IDs of the subnets. You can specify only one subnet per Availability Zone. You must specify either subnets or subnet mappings.
[Application Load Balancers] You must specify subnets from at least two Availability Zones. When you specify subnets for an existing Application Load Balancer, they replace the previously enabled subnets.
Thus, you need to add Subnets to your Load Balancer definition. It must be at least two subnets, each in different Availability Zones.