AWS CloudFormation Concepts: Difference between revisions
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If (and when) creating a service role, CloudFormation is identified as "cloudformation.amazonaws.com". | If (and when) creating a service role, CloudFormation is identified as "cloudformation.amazonaws.com". | ||
=Built-In Variables= | |||
"Variables", in lack of a better name: | |||
====AWS::StackName==== | |||
====AWS::Region==== | |||
Revision as of 19:27, 13 March 2019
External
Internal
Overview
CloudFormation creates and configures resources, grouped in stacks. The resource declarations are provided as templates. One of the greatest benefits of templates and AWS CloudFormation is the ability to create a set of resources that work together to create an application or solution.
Bootstrapping Application via WS CloudFormation
Stack
A stack is a collection of AWS resources that can be managed (create, update or delete) as a single unit. Every stack is based on a template: all resources in a stack are defined by the stack's AWS CloudFormation template. Because AWS CloudFormation treats the stack resources as a single unit, they must all be created or deleted successfully for the stack to be created or deleted. If a resource cannot be created, AWS CloudFormation rolls the stack back and automatically deletes any resources that were created. If a resource cannot be deleted, any remaining resources are retained until the stack can be successfully deleted.
Nested Stack
A nested stack is a stack created as part of other stacks.
Root Stack
Stack Operations
Template
A template is a declaration of AWS resources that make up a stack. The template describes what resources are needed, and AWS CloudFormation provisions those resources in an orderly and. predictable fashion. The resources are created in parallel where possible. AWS CloudFormation deals with failure and transient issues. The templates are stored as JSON or YAML text files.
Template Structure
---
AWSTemplateFormatVersion: "version date"
Description:
<String>
Metadata:
<template metadata>
Parameters:
<set of parameters>
Mappings:
<set of mappings>
Conditions:
<set of conditions>
Transform:
<set of transforms>
Resources:
<set of resources - the only required top-level object>
Outputs:
<set of outputs>
AWSTemplateFormatVersion
Description
Input Parameters
The input parameters are declared in a template's Parameters object. A parameter contains a list of attributes that define its value and constraints against its value. The only required attribute is Type, which can be a String, Number or an AWS-specific type.
Parameters:
WebServerPort:
Default: 8888
Description: TCP/IP port for the WordPress web server
Type: Number
MinValue: 1
MaxValue: 65535
For AWS-specific parameter types, AWS CloudFormation validates input values against existing values in the user's AWS account and in the region where he or she is creating the stack before creating any stack resources.
Validation Constraints
- MinLength
- MaxLength
- Default
- AllowedValues
- AllowedPattern
Parameter Description
The parameter description is important, as it will show up in the dynamically-generated CloudFormation console (wizard) while creating the stack. Specifying examples and details is a good idea.
Metadata
Metadata section is optional, and provides information about the template itself. These details may include implementation details for specific resources.
Keys:
- AWS::CloudFormation::Init
- AWS::CloudFormation::Interface: Defines the grouping and ordering of input parameters when they are displayed in the AWS CloudFormation console. By default, the AWS CloudFormation console alphabetically sorts parameters by their logical ID.
- AWS::CloudFormation::Designer: describes how resources are laid out in the AWS CloudFormation Designer.
Conditions
The optional Conditions section contains statements that define the circumstances under which entities are created or configured.
Mappings
Resources
Resources:
<ResourceName>:
Type: <mandatory-type>
Properties: ...
A resource must have a Type attribute, which defines the kind of AWS resource should be created.
AWS::ProductIdentifier::ResourceType
Full list of resource types:
Resource declarations use a Properties attribute to specify the information used to create a resource.
Resource Name
The name used for a resource within the template is a logical name. When AWS CloudFormation creates the resource, it generates a physical name that is based on the combination of the logical name, the stack name, and a unique ID.
Resource Types
Change Set
Function
AWS CloudFormation has a number of intrinsic functions that can be used to refer to other resources and their properties.
Intrinsic Functions
Ref, Join, Split, etc:
Condition Functions
Drift
CloudFormation Designer
CloudFormation Service Role
If (and when) creating a service role, CloudFormation is identified as "cloudformation.amazonaws.com".
Built-In Variables
"Variables", in lack of a better name: