Template structure (JSON/YAML) in AWS - Step-by-Step Execution

Process Flow - Template structure (JSON/YAML)

Start Template

↓

Version

↓

Declare Parameters

↓

Define Resources

↓

Set Outputs

↓

End Template

This flow shows the main parts of an AWS CloudFormation template from start to finish.

Execution Sample

AWS

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Parameters": {},
  "Resources": {},
  "Outputs": {}
}

A minimal AWS CloudFormation template structure in JSON format.

Process Table

Step	Section	Action	Details	Result
1	Start Template	Begin parsing	Recognize template start	Template parsing started
2	Version	Read AWSTemplateFormatVersion	Version set to 2010-09-09	Version recorded
3	Parameters	Check for parameters	None defined here	No parameters to process
4	Resources	Check for resources	None defined here	No resources to create
5	Outputs	Check for outputs	None defined here	No outputs to return
6	End Template	Finish parsing	Template fully parsed	Template ready for deployment

💡 Template parsing ends after reading all main sections.

Status Tracker

Variable	Start	After Version	After Parameters	After Resources	After Outputs	Final
AWSTemplateFormatVersion	undefined	2010-09-09	2010-09-09	2010-09-09	2010-09-09	2010-09-09
Parameters	undefined	undefined	{}	{}	{}	{}
Resources	undefined	undefined	undefined	{}	{}	{}
Outputs	undefined	undefined	undefined	undefined	{}	{}

Key Moments - 3 Insights

Why do we need the AWSTemplateFormatVersion section?

It tells AWS which version of the template format you are using, ensuring compatibility. See execution_table step 2.

What happens if no Resources are defined?

No AWS resources will be created or changed. The template is valid but does nothing. See execution_table step 4.

Can Outputs be empty?

Yes, Outputs are optional and can be empty if you don't need to return any information after deployment. See execution_table step 5.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result after reading the Parameters section?

A Parameters are undefined

B Parameters contain resource definitions

C Parameters are set to an empty object {}

D Parameters cause an error

💡 Hint

Check execution_table row 3 under Result column.

At which step does the template parsing finish?

A Step 5

B Step 6

C Step 4

D Step 2

💡 Hint

Look at the last row in execution_table for the End Template step.

If you add a resource to the Resources section, which variable changes in variable_tracker?

A Resources

B Parameters

C AWSTemplateFormatVersion

D Outputs

💡 Hint

Resources variable changes after the Resources section is processed.

Concept Snapshot

AWS CloudFormation template structure:
- Start with AWSTemplateFormatVersion
- Define Parameters (optional inputs)
- Define Resources (AWS services to create)
- Define Outputs (optional results)
Each section is a JSON/YAML key
Templates must be valid JSON or YAML

Full Transcript

An AWS CloudFormation template is a text file in JSON or YAML format. It starts with a version declaration called AWSTemplateFormatVersion. Then it can have Parameters to accept inputs, Resources to define AWS services to create, and Outputs to return information after deployment. The template is read from top to bottom. If any section is missing, it is treated as empty. The template must be valid JSON or YAML to deploy successfully.

Practice

1. What is the main purpose of a cloud template written in JSON or YAML?

easy

A. To manually configure cloud resources one by one

B. To write application code for cloud functions

C. To monitor cloud resource usage in real-time

D. To describe and set up cloud resources automatically

Solution

1. Step 1: Understand what a cloud template does

   A cloud template is a file that describes cloud resources and how to create them automatically.

2. Step 2: Compare options with this purpose

   Only To describe and set up cloud resources automatically matches this description; others describe different tasks.

3. Final Answer:

   To describe and set up cloud resources automatically -> Option D

4. Quick Check:

   Cloud templates automate resource setup = D [OK]

Hint: Templates automate resource setup, not manual or monitoring tasks [OK]

Common Mistakes:

• Confusing templates with monitoring tools
• Thinking templates are for writing application code
• Assuming templates require manual resource setup

2. Which of the following is the correct top-level section name in an AWS CloudFormation JSON template?

easy

A. Resources

B. Scripts

C. Functions

D. Commands

Solution

1. Step 1: Recall AWS CloudFormation template structure

   The main sections include Parameters, Resources, Outputs, etc. 'Resources' defines the cloud resources.

2. Step 2: Identify valid section names

   Only 'Resources' is a valid top-level section; others are not used in CloudFormation templates.

3. Final Answer:

   Resources -> Option A

4. Quick Check:

   Resources section defines cloud resources = C [OK]

Hint: Remember: Resources section always defines cloud items [OK]

Common Mistakes:

• Using non-existent sections like Scripts or Commands
• Confusing function code with template sections
• Mixing up template sections with programming terms

3. Given this snippet of a CloudFormation JSON template:

{
  "Resources": {
    "MyBucket": {
      "Type": "AWS::S3::Bucket"
    }
  }
}

What resource will this template create?

medium

A. An EC2 virtual server

B. An S3 storage bucket

C. A Lambda function

D. A VPC network

Solution

1. Step 1: Read the resource type in the template

   The resource type is "AWS::S3::Bucket", which means an S3 storage bucket.

2. Step 2: Match resource type to options

   Only An S3 storage bucket matches the S3 bucket resource type.

3. Final Answer:

   An S3 storage bucket -> Option B

4. Quick Check:

   "AWS::S3::Bucket" means S3 bucket = B [OK]

Hint: Look for "Type" value to identify resource created [OK]

Common Mistakes:

• Confusing S3 bucket with EC2 or Lambda
• Ignoring the resource type string
• Assuming resource names define type

4. You wrote this YAML snippet for a CloudFormation template but it fails to deploy:

Resources:
  MyInstance:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: ami-12345678
      InstanceType: t2.micro
      SecurityGroups: my-security-group

What is the likely error?

medium

A. InstanceType is invalid for EC2

B. ImageId must be a number, not a string

C. SecurityGroups should be a list, not a single string

D. Resources section name is misspelled

Solution

1. Step 1: Check the SecurityGroups property format

   SecurityGroups expects a list of strings, but here it is a single string.

2. Step 2: Validate other properties

   ImageId is a string (correct), InstanceType is valid, Resources is spelled correctly.

3. Final Answer:

   SecurityGroups should be a list, not a single string -> Option C

4. Quick Check:

   SecurityGroups needs list format = A [OK]

Hint: Lists must be in brackets or dash format in YAML [OK]

Common Mistakes:

• Using string instead of list for SecurityGroups
• Assuming ImageId is numeric
• Misspelling Resources section

5. You want to create a reusable CloudFormation template that accepts a bucket name as input and outputs the bucket ARN. Which two sections must you include in your JSON template?

hard

A. Parameters and Outputs

B. Resources and Scripts

C. Functions and Parameters

D. Outputs and Commands

Solution

1. Step 1: Identify input and output sections needed

   To accept input like bucket name, use Parameters. To show output like ARN, use Outputs.

2. Step 2: Confirm other sections are invalid

   Scripts, Functions, Commands are not valid top-level sections in CloudFormation templates.

3. Final Answer:

   Parameters and Outputs -> Option A

4. Quick Check:

   Input = Parameters, Output = Outputs [OK]

Hint: Parameters take inputs; Outputs show results [OK]

Common Mistakes:

• Using non-existent sections like Scripts or Commands
• Confusing Resources with input/output sections
• Forgetting to include Outputs for results