Building Blocks

Templates components

• Resources: AWS resources declared in the template (can use !Ref function to refer to others resources in the same YAML file)
• Parameters: the dynamic inputs (use with !Ref function)
• Mappings: the static variables (use with !FindInMap[ MapName, TopLevelKey, SecondLevelKey ] function)
• Outputs: export to be used by other stacks (other stacks use !ImportValue function to reference). Exported output names must be unique within region
• Conditionals: List of conditions to perform resource creation (!If, !Not, !Equal...)
• Metadata

Templates helpers:

• References
• Functions

Rollbacks

• Stack Creation Fails:
  • Default: everything rolls back (gets deleted)
  • Option to disable rollback and troubleshoot what happened
• Stack Update Fails:
  • The stack automatically rolls back to the previous known working state
  • Ability to see in the log what happened and error messages

Tips:

• Can I create a dynamic amount of resources?

  • No, you can't. Everything in CloudFormation templates has to be declared. Can't perform code generation here

• Is every AWS Service supported in CloudFormation's resources?

  • Almost. Only a select few niches are not there yet
  • You can work around that using AWS Lambda Custom Resources

• Exported output names must be unique within region

• !GetAtt