AWS Cloud Formation

 AWS Cloud Formation Template is used to automate the workload component creation using simple scripts on the cloud. Cloud Formation is an Infrastructure-as-a-code (IaaC) offering from AWS. Cloud Formation templates are similar to Terraform / Chef / Ansible- however aren't cloud agnostic. Cloud Formation templates can only be applied on AWS Cloud.

Templates

• it's a text file / YAML or JSON
• it's an input to cloud formation, used to build AWS resources
• it describes the end state of the infrastructure

Stack

• When Cloud Formation executes a template, it creates a stack.
• To update resources within a template, need to update the stack
• A set of related resources, as a single unit is called a stack

Change set

• Summarizes the impact of the update to template before applying to the stack
• Summary helps analyze the impact to live systems in PROD
• impact to existing AWS resources helps take preventive action before applying the stack update

Cloud formation template sections

• JSON or YAML definition file
• AWSTemplateFormatVersion, only valid value 2010-09-09, optional
• Description, optional
• Metadata, provides additional info about the template, optional
• Parameters, allows to pass values into the template at runtime, optional
• Mapping, set of keys & values operate as a lookup table, optional
• Conditions, place conditions to examine whether resources are created, optional
• Transform, specify transforms that cloud formation uses to process the template, optional
• Resources, defines stack resources & their properties
• Outputs, allows to return output from the stack

Intrinsic functions - "Fn::Join": "delim", [comma separated list of values]

Multiple resources - use the same script to configure multiple resources

• most commonly used since a single script covers creating all required resources

 Pseudo parameters - similar to global variables, are also intrinsic variables

 Reference

1. AWS Cloud Formation