AiL – Baby’s First CloudFormation Stack

As previously discussed, I’m doing a small series of posts around bringing the AWS infrastructure that I use into the current era, and putting it all into CloudFormation. In this post, I’m going to cover setting up the first stack. This is going to set up a Virtual Private Cloud (or VPC), which is where the rest of the stuff I make later will sit.

What’s a Virtual Private Cloud?

A VPC is a virtual network of virtual servers. It’s your own mini-slice of the AWS cloud, and the machines within the VPC are aware of each other – in fact, they are on their own subnet (or subnets).

Why use a VPC?

You don’t have to set up a VPC to use AWS. You can simply create servers. That’s what I’ve been doing up until now. It’s just that it’s a bit limited.

I want to use a VPC for two big reasons:

  • I want to be able to use more recent/powerful/cheaper machine images, with OpsWorks. They’re only available if I also use a VPC.
  • I want to use an Elastic Load Balancer, in part to manage HTTPS certificates and connections. This requires a VPC and subnets.

Setting up the Stack

Here’s my config, at this particular stage:

AWSTemplateFormatVersion: '2010-09-09'
Global configuration that could be used by multiple related stacks
# Metadata: # no metadata
Type: String
Stack Environment Prefix.
# We need at least one resource. The VPC is the logical one to include here.
Type: AWS::EC2::VPC
# The range of ip addresses used in the VPC. Subnets will be inside this.
# Using the /16 lets me easily have subnets that don't overlap without
# needing to remember bit masks.
CidrBlock: # ->
EnableDnsSupport: true # If false, the servers don't seem to get access to DNS at all.
InstanceTenancy: default
- Key: Name
Value: !Sub "${Environment} VPC"
Description: The ID for the Virtual Private Cloud; needed by more or less everything.
Value: !Ref VPC
Name: !Sub "${Environment}::VPC"
view raw Globals.yaml hosted with ❤ by GitHub

I put the VPC into its own file, because I don’t want to delete it when tearing down an environment for the sake of testing. There’s lots of things that get annoying to re-create if the VPC is changed (cough OpsWorks stacks) – so we put the VPC in its own file. (Later, when I bring in nested stacks, this will not be in the nested stack).

Break It Down

First, note that I use YAML for my CloudFormation files. I’m not a huge fan of YAML in general, but the JSON option doesn’t allow you to use comments, and comments are essential. (Sidebar: when parsing JSON, always enable comments. It’s non-standard, but it’s useful). Using YAML also lets me use a more convenient shorthand for accessing some inbuilt functions (the Sub one is used here). I strongly suggest you do the same.

The Parameters block provides me with some configuration options. It allows me, if I want, to create different instances of the stack. In this case, I use an Environment parameter. This particular parameter is common to all my stack files, and I use it to separate test stacks from the prod ones. (I could also do this with AWS sub-accounts)

The Resources block specifies what this file provides. Here I set up the Virtual Private Cloud.

Finally, in the Outputs section, I export the VPC reference out, so that other files can link to it.

Author: Robert Watkins

My name is Robert Watkins. I am a software developer and have been for over 20 years now. I currently work for people, but my opinions here are in no way endorsed by them (which is cool; their opinions aren’t endorsed by me either). My main professional interests are in Java development, using Agile methods, with a historical focus on building web based applications. I’m also a Mac-fan and love my iPhone, which I’m currently learning how to code for. I live and work in Brisbane, Australia, but I grew up in the Northern Territory, and still find Brisbane too cold (after 22 years here). I’m married, with two children and one cat. My politics are socialist in tendency, my religious affiliation is atheist (aka “none of the above”), my attitude is condescending and my moral standing is lying down.

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