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Category Archives: AWS

Example AWS CloudFormation template for network load balancer


We needed a public network load balancer with SSL (through AWS Certificate Manager) and took me some retry’s to get it right since most examples are based upon the classic or application load balancer so here to share:

  Terra10NetworkLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Name: t10-networkloadbalancer
      Scheme: internet-facing
      Subnets: !Ref Terra10Subnet
      Type: network
      Tags:
        - Key: Name
          Value: t10-networklb
  Terra10NetworkLoadBalancerTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      Name: t10-networklb-target
      Port: 443
      Protocol: TCP
      VpcId: !ImportValue t10-vpc-id
      TargetGroupAttributes:
        - Key: deregistration_delay.timeout_seconds
          Value: 60
      Targets:
      - Id: !Ref Terra10EC2Instance1
        Port: 443
      - Id: !Ref Terra10EC2Instance2
        Port: 443  
      Tags:
        - Key: Name
          Value: t10-networklb-target
  Terra10NetworkLoadBalancerListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
      - Type: forward
        TargetGroupArn: !Ref Terra10NetworkLoadBalancerTargetGroup
      LoadBalancerArn: !Ref Terra10NetworkLoadBalancer
      Port: '443'
      Protocol: TCP
  Terra10NetworkLoadBalancerListenerCert:
    Type: AWS::ElasticLoadBalancingV2::ListenerCertificate
    Properties:
      Certificates:
        - CertificateArn: arn:aws:acm:eu-west-1:xxxaccountxxx:certificate/123456....
      ListenerArn: !Ref Terra10NetworkLoadBalancerListener

 

Reference

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Posted by on 29-08-2018 in AWS, CloudFormation

 

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How to share values between seperated AWS CloudFormation stacks

In AWS CloudFormation templates you often have the need to make a reference to an earlier created component. For instance the unique ID of a vpc, subnet, security group or instance. You have two choices: continue with separated stacks or combine them to create a nested stack. In our case we wanted to keep seperated stacks so needed a way to export/import settings from an earlier network related CloudFormation stack holding our VPC and Subnet Identifier which the new stack uses. To share information between stacks we can export output values from the first stack and import these values in new stacks. Other stacks that are in the same AWS account and region can import the exported values.

Example of an VPC ID which we export in our network stack (named t10-cf-vpc):

######################
## OUTPUT
######################
Outputs:
    VPC:
        Description: A reference to the created VPC
        Value: !Ref VPC
        Export:
          Name: t10-vpc-id

You can easily check if the export succeeded by using the AWS CloudFormation GUI

or using the AWS CLI to get a list

 
jvzoggel$ aws cloudformation list-exports
{
"Exports": [
{
"ExportingStackId": "arn:aws:cloudformation:xxxxx:xxxxxxx:stack/t10-cf-vpc/xxxxxxxx",
"Name": "t10-vpc-id",
"Value": "vpc-xxxxxxx"
},
.....

Importing the values in new stacks

The new CloudFormation stack can make use of the exported value simple by using the !ImportValue function

Parameters:
  NetworkStackNameParameter:
    Description: Reference to the vpc-10 stack
    Type: String
    Default: 't10-cf-vpc'

Resources:
  MyTerra10SecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupName: MyTerra10SecurityGroup
      GroupDescription: MyTerra10SecurityGroup
      VpcId: !ImportValue t10-vpc-id

Note: After another stack imports an output value, you can’t delete the stack that is exporting the output value or modify the exported output value.

References:

 
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Posted by on 28-08-2018 in AWS

 

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Using CloudFormation to bootstrap EC2 instances with scripts from CodeCommit

While spinning up EC2 instances you can bootstrap them with packages, files, etc in different ways. For our stack we wanted to pull scripts from an AWS CodeCommit to make life easier.

The (bash) scripts are stored in our CodeCommit so first we need to make sure the EC2 instances, while spinning up, are allowed to access the repository. So we created an IAM Policy with these sufficient rights and attach the policy to a IAM role which we can use to attach to our EC2 instances.

AWS IAM Policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "codecommit:GitPull"
            ],
            "Resource": "arn:aws:codecommit:*:*:terra10-scripts"
        },
        {
            "Effect": "Allow",
            "Action": [
                "codecommit:Get*",
                "codecommit:BatchGetRepositories",
                "codecommit:List*"
            ],
            "Resource": "*"
        }
    ]
}

We make sure the EC2 instances uses the new IAM Role by defining IamInstanceProfile with our example IAM Role t10-ec2-role in the CloudFormation template. Further on by using the UserData segment we can execute scripts during bootstrap of the server. Install the AWSCLI is required for the credential helper

T10Controller1:
  Type: AWS::EC2::Instance
  Properties:
    ImageId: !Ref HostAMI
    InstanceType: t2.micro
    IamInstanceProfile: t10-ec2-role
    PrivateIpAddress: 10.0.11.11   
    Tags:
      - Key: Name
        Value: t10-k8s-controller1
    UserData:
      Fn::Base64: !Sub |
        #!bin/bash -xe
        apt-get update
        apt-get -y install awscli
        cd /tmp
        echo "######## git pull AWS CodeCommit files"
        sudo git config --global credential.helper '!aws codecommit credential-helper $@'
        sudo git config --global credential.UseHttpPath true
        sudo git clone https://git-codecommit.xxxxxx.amazonaws.com/v1/repos/terra10-scripts /tmp/terra10-scripts

 

 
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Posted by on 26-08-2018 in AWS

 

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AWS CloudFormation error “The parameter groupName cannot be used with the parameter subnet”

When trying to start some EC2 instance through CloudFormation I kept getting the error “The parameter groupName cannot be used with the parameter subnet”.  

The (YAML) AWS CloudFormation looks something like this:

Resources:
  KubernetesControllerSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupName: t10-sg-k8s-controller
      GroupDescription: t10-sg-k8s-controller
      ......
      Tags:
        - Key: Name
          Value: t10-sg-k8s-controller
  EC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: ami-20ee5e5d
      InstanceType: t2.micro
      KeyName: t10_kubernetes
      PrivateIpAddress: 10.0.11.11
      SubnetId:
        Fn::ImportValue:
          !Sub "t10-vpc-k8s-subnet1-id"
      SecurityGroupIds: - !Ref KubernetesControllerSecurityGroup
      Tags:
        - Key: Name
          Value: t10-k8s-controller1

So the error ended in a Google search with many hits, many questions, many suggestions, but very few real answers.

Until I saw this answer from johnhunsley:
I believe you have created a Security Group without specifying a VPC ID. You have then attempted to create a launch config which launches instances into a subnet within a VPC. Therefore, when It attempts to assign the security group to those instances it fails because it expects the security group ID rather than the name.

So I think the response from AWS is in the running for the “Worst Error Message Ever” but the solution is very simple. Don’t make the mistake of not specifying your custom VPC ID when creating a new security group.

Resources:
  KubernetesControllerSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupName: t10-sg-k8s-controller
      GroupDescription: t10-sg-k8s-controller
      ......
      VpcId: !ImportValue t10-vpc-id
      Tags:
        - Key: Name
          Value: t10-sg-k8s-controller

References

johnhunsley @ https://github.com/boto/boto/issues/350

 
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Posted by on 15-08-2018 in AWS, CloudFormation

 

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