AWS Classroom Series – 21/May/2020

References and concepts

• Refer
• Install Visual Studio Code and Cloudformation Extension
• Format Version
• Preview of Workflows

Cloudformation Resources

• Refer Here
• In Resources section we describe/declare what resources have to be created.

"Resources" : {
    "Logical ID" : {
        "Type" : "Resource type",
        "Properties" : {
            Set of properties
        }
    }
}

Resources:
  Logical ID:
    Type: Resource type
    Properties:
      Set of properties

• Logical ID is unique id given by template designer/creator
• Every resource in AWS has a unique type and it will have set of properties
• In the Resources section, we create multiple resources as per the needs of the application / infra to be deployed

Cloudformation template to create a vpc with 4 subnets

• Make a note of manual steps
  • Create a vpc
  • Create subnet1 and select the vpc created above
  • Add three more subnets in the same way
• Create a new folder ‘vpc’ and add a file ‘vpc.json’ to it
• Now lets add the basic structure with Description and template version

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "This template is written for learning and it creates vpc with 4 subnets",
}

• Now since we need to create vpc, lets add resources section

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "This template is written for learning and it creates vpc with 4 subnets",
    "Resources": {
        
    }
}

• Lets find aws vpc cloudformation resource docs Refer Here and also look into resources section from here and then fill the template

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "This template is written for learning and it creates vpc with 4 subnets",
    "Resources": {
        "myvpc": {
            "Type": "AWS::EC2::VPC",
            "Properties": {
                "CidrBlock": "10.0.0.0/16",
                "EnableDnsHostnames": true,
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "myvpc"
                    }
                ]
            }
        }

    }
}

• Hint: If you have installed vscode extension as mentioned above, you get help (intellisense) from vscode
• Now we need to add subnets, As shown below, we need vpc id
• Lets add one subnet resource Refer Here.
• While creating template for subnet i need to give vpc id which is not yet created/known i.e. resource with subnet1 id is depending on resource with myvpc id

"subnet1": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "CidrBlock": "10.0.0.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet1"
                    }
                ],
                "VpcId": 

            }
        }

• Now lets look at documentation of vpc cf resource and navigate to Return Values section
• According to docs lets refer Ref section over here
• So adding reference to myvpc in subnet1

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "This template is written for learning and it creates vpc with 4 subnets",
    "Resources": {
        "myvpc": {
            "Type": "AWS::EC2::VPC",
            "Properties": {
                "CidrBlock": "10.0.0.0/16",
                "EnableDnsHostnames": true,
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "myvpc"
                    }
                ]
            }
        },
        "subnet1": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "CidrBlock": "10.0.0.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet1"
                    }
                ],
                "VpcId": {
                    "Ref": "myvpc"
                }
            }
        }
    }
}

• Now adding other 3 subnets to cf template

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "This template is written for learning and it creates vpc with 4 subnets",
    "Resources": {
        "myvpc": {
            "Type": "AWS::EC2::VPC",
            "Properties": {
                "CidrBlock": "10.0.0.0/16",
                "EnableDnsHostnames": true,
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "myvpc"
                    }
                ]
            }
        },
        "subnet1": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "CidrBlock": "10.0.0.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet1"
                    }
                ],
                "VpcId": {
                    "Ref": "myvpc"
                }
            }
        },
        "subnet2": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "VpcId": {
                    "Ref": "myvpc"
                },
                "CidrBlock": "10.0.1.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet2"
                    }
                ]
            }
        },
        "subnet3": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "VpcId": {
                    "Ref": "myvpc"
                },
                "CidrBlock": "10.0.2.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet3"
                    }
                ]
            }
        },
        "subnet4": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "VpcId": {
                    "Ref": "myvpc"
                },
                "CidrBlock": "10.0.3.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet4"
                    }
                ]
            }
        }
    }
}

• Now execute this tempalte and look into results
• Now if we were asked to create subnet1 in AZ -a subnet2 in Az B etc we need to understand the impact of the change which is mentioned in Update Requires section in Parameter

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Description": "This template is written for learning and it creates vpc with 4 subnets",
    "Resources": {
        "myvpc": {
            "Type": "AWS::EC2::VPC",
            "Properties": {
                "CidrBlock": "10.0.0.0/16",
                "EnableDnsHostnames": true,
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "myvpc"
                    }
                ]
            }
        },
        "subnet1": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "CidrBlock": "10.0.4.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet1"
                    }
                ],
                "VpcId": {
                    "Ref": "myvpc"
                },
                "AvailabilityZone": "ap-south-1a"
            }
        },
        "subnet2": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "VpcId": {
                    "Ref": "myvpc"
                },
                "CidrBlock": "10.0.5.0/24",

                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet2"
                    }
                ]
                ,
                "AvailabilityZone": "ap-south-1b"
            }
        },
        "subnet3": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "VpcId": {
                    "Ref": "myvpc"
                },
                "CidrBlock": "10.0.6.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet3"
                    }
                ]
                ,
                "AvailabilityZone": "ap-south-1c"
            }
        },
        "subnet4": {
            "Type": "AWS::EC2::Subnet",
            "Properties": {
                "VpcId": {
                    "Ref": "myvpc"
                },
                "CidrBlock": "10.0.7.0/24",
                "Tags": [
                    {
                        "Key": "Name",
                        "Value": "subnet4"
                    }
                ]
                ,
                "AvailabilityZone": "ap-south-1a"
            }
        }
    }
}

• Now if we execute this, new subnets will be created when the stack is updated
• After updating the stack succesfully compare subnet ids

Summary

• Format Version
• Resources
• Visual Studio Code Extension
• Reference
• Update Requires