Amazon Web Services CloudFormationis a free service that provides Amazon Web Service (AWS) customers with the tools they need to create and manage the infrastructure a particular software application requires to run on Amazon Web Services
CloudFormation has two parts: templates and stacks. A template is a JavaScript Object Notation (JSON) text file. The file, which is declarative and not scripted, defines what AWS resources or non-AWS resources are required to run the application. ( I will walk you through with the example at the end of this article )
When the template is submitted to the service, CloudFormation creates the necessary resources in the customer's account and builds a running of the template, putting dependencies and data flows in the right order automatically. The running instance is called a stack.
We can make changes to the stack after it’s been deployed by using CloudFormation tools and an editing process that is similar to version control. When a stack is deleted, all related resources are deleted automatically as well.
advantage of CloudFormation is that it allows developers to automate service provisioning steps in a fairly simple way. There is no extra charge for AWS CloudFormation; customers only pay for the AWS resources that are required to run their applications.
Example
Below is self explanatory example of sample template
{
"AWSTemplateFormatVersion" : "2010-09-09",
##This is mandatory
"Description" : "AWS CloudFormation Sample Template EC2_Instance_With_Ephemeral_Drives: Example to show how to attach ephemeral drives using EC2 block device mappings. **WARNING** This template creates an Amazon EC2 instance. You will be billed for the AWS resources used if you create a stack from this template.",
"Parameters" : {
"KeyName": {
"Description" : "Name of an existing EC2 KeyPair to enable SSH access to the web server",
"Type": "AWS::EC2::KeyPair::KeyName",
"ConstraintDescription" : "must be the name of an existing EC2 KeyPair."
},
##This is parameter for spinningup new EC2-Instance and its pre-requsites
"InstanceType" : {
"Description" : "WebServer EC2 instance type",
"Type" : "String",
"Default" : "t2.small", ## Instance type , there are lot more instance type but I choose t2.small for example
"ConstraintDescription" : "must be a valid EC2 instance type."
},
"SSHLocation": {
"Description": "Lockdown SSH access to the bastion host (default can be accessed from anywhere)",
"Type": "String",
"MinLength": "9",
"MaxLength": "18",
"Default": "0.0.0.0/0", ##Mandatory field as we need to access server from IP range , 0.0.0.0/0 means over the internet and nyone can access it
"AllowedPattern": "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})/(\\d{1,2})",
"ConstraintDescription": "must be a valid CIDR range of the form x.x.x.x/x."
}
},
"Mappings" : {
"AWSInstanceType2Arch" : {
"t1.micro" : { "Arch" : "PV64" }
},
"AWSRegionArch2AMI" : { #provide region and their respectvie images (AMID with ID)
"us-east-1" : {"PV64" : "ami-2a69aa47", "HVM64" : "ami-6869aa05", "HVMG2" : "ami-920f8984"},
"us-west-2" : {"PV64" : "ami-7f77b31f", "HVM64" : "ami-7172b611", "HVMG2" : "ami-54d44234"}
},
"Resources" : {
"EC2Instance" : {
"Type" : "AWS::EC2::Instance",
"Properties" : {
"KeyName" : { "Ref" : "KeyName" },
"InstanceType" : { "Ref" : "InstanceType" },
"ImageId" : { "Fn::FindInMap" : [ "AWSRegionArch2AMI", { "Ref" : "AWS::Region" },
{ "Fn::FindInMap" : [ "AWSInstanceType2Arch", { "Ref" : "InstanceType" }, "Arch" ] } ] },
"SecurityGroups" : [{ "Ref" : "EC2SecurityGroup" }],
"BlockDeviceMappings" : [
{
"DeviceName" : "/dev/sdc",
"VirtualName" : "ephemeral0"
}
]
}
},
"EC2SecurityGroup" : {
"Type" : "AWS::EC2::SecurityGroup", #this will create secutiry group with given ingress rule port number and cidr range
"Properties" : {
"GroupDescription" : "SSH access",
"SecurityGroupIngress" : [{ "IpProtocol" : "tcp", "FromPort" : "22", "ToPort" : "22", "CidrIp" : { "Ref" : "SSHLocation" }}]
}
}
},
"Outputs" : {
"Instance" : {
"Value" : { "Fn::GetAtt" : [ "EC2Instance", "PublicDnsName" ] },
"Description" : "DNS Name of the newly created EC2 instance"
}
}
}
