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In some cases, you might want to create stacks that are similar but with minor tweaks. For example, you might have a template that you use for production applications. You want to create the same production stack so that you can use it for development or testing. However, for development and testing, you might not require all the extra capacity that's included in a production-level stack. Instead, you can use an environment type input parameter in order to conditionally create stack resources that are specific to production, development, or testing, as shown in the following sample:
{
"AWSTemplateFormatVersion" : "2010-09-09",
"Mappings" : {
"RegionMap" : {
"us-east-1" : { "AMI" : "ami-0ff8a91507f77f867"},
"us-west-1" : { "AMI" : "ami-0bdb828fd58c52235"},
"us-west-2" : { "AMI" : "ami-a0cfeed8"},
"eu-west-1" : { "AMI" : "ami-047bb4163c506cd98"},
"sa-east-1" : { "AMI" : "ami-07b14488da8ea02a0"},
"ap-southeast-1" : { "AMI" : "ami-08569b978cc4dfa10"},
"ap-southeast-2" : { "AMI" : "ami-09b42976632b27e9b"},
"ap-northeast-1" : { "AMI" : "ami-06cd52961ce9f0d85"}
}
},
"Parameters" : {
"EnvType" : {
"Description" : "Environment type.",
"Default" : "test",
"Type" : "String",
"AllowedValues" : ["prod", "dev", "test"],
"ConstraintDescription" : "must specify prod, dev, or test."
}
},
"Conditions" : {
"CreateProdResources" : {"Fn::Equals" : [{"Ref" : "EnvType"}, "prod"]},
"CreateDevResources" : {"Fn::Equals" : [{"Ref" : "EnvType"}, "dev"]}
},
"Resources" : {
"EC2Instance" : {
"Type" : "AWS::EC2::Instance",
"Properties" : {
"ImageId" : { "Fn::FindInMap" : [ "RegionMap", { "Ref" : "AWS::Region" }, "AMI" ]},
"InstanceType" : { "Fn::If" : [
"CreateProdResources",
"c1.xlarge",
{"Fn::If" : [
"CreateDevResources",
"m1.large",
"m1.small"
]}
]}
}
},
"MountPoint" : {
"Type" : "AWS::EC2::VolumeAttachment",
"Condition" : "CreateProdResources",
"Properties" : {
"InstanceId" : { "Ref" : "EC2Instance" },
"VolumeId" : { "Ref" : "NewVolume" },
"Device" : "/dev/sdh"
}
},
"NewVolume" : {
"Type" : "AWS::EC2::Volume",
"Condition" : "CreateProdResources",
"Properties" : {
"Size" : "100",
"AvailabilityZone" : { "Fn::GetAtt" : [ "EC2Instance", "AvailabilityZone" ]}
}
}
}
}
AWSTemplateFormatVersion: "2010-09-09"
Mappings:
RegionMap:
us-east-1:
AMI: "ami-0ff8a91507f77f867"
us-west-1:
AMI: "ami-0bdb828fd58c52235"
us-west-2:
AMI: "ami-a0cfeed8"
eu-west-1:
AMI: "ami-047bb4163c506cd98"
sa-east-1:
AMI: "ami-07b14488da8ea02a0"
ap-southeast-1:
AMI: "ami-08569b978cc4dfa10"
ap-southeast-2:
AMI: "ami-09b42976632b27e9b"
ap-northeast-1:
AMI: "ami-06cd52961ce9f0d85"
Parameters:
EnvType:
Description: Environment type.
Default: test
Type: String
AllowedValues: [prod, dev, test]
ConstraintDescription: must specify prod, dev, or test.
Conditions:
CreateProdResources: !Equals [!Ref EnvType, prod]
CreateDevResources: !Equals [!Ref EnvType, "dev"]
Resources:
EC2Instance:
Type: "AWS::EC2::Instance"
Properties:
ImageId: !FindInMap [RegionMap, !Ref "AWS::Region", AMI]
InstanceType: !If [CreateProdResources, c1.xlarge, !If [CreateDevResources, m1.large, m1.small]]
MountPoint:
Type: "AWS::EC2::VolumeAttachment"
Condition: CreateProdResources
Properties:
InstanceId: !Ref EC2Instance
VolumeId: !Ref NewVolume
Device: /dev/sdh
NewVolume:
Type: "AWS::EC2::Volume"
Condition: CreateProdResources
Properties:
Size: 100
AvailabilityZone: !GetAtt EC2Instance.AvailabilityZone
You can specify `prod`, `dev`, or `test` for the `EnvType` parameter. For each environment type, the template specifies a different instance type. The instance types can range from a large, compute-optimized instance type to a small general purpose instance type. In order to conditionally specify the instance type, the template defines two conditions in the Conditions section of the template: `CreateProdResources`, which evaluates to true if the `EnvType` parameter value is equal to `prod` and `CreateDevResources`, which evaluates to true if the parameter value is equal to `dev`.
In the `InstanceType` property, the template nests two `Fn::If` intrinsic functions to determine which instance type to use. If the `CreateProdResources` condition is true, the instance type is `c1.xlarge`. If the condition is false, the `CreateDevResources` condition is evaluated. If the `CreateDevResources` condition is true, the instance type is `m1.large` or else the instance type is `m1.small`.
In addition to the instance type, the production environment creates and attaches an Amazon EC2 volume to the instance. The `MountPoint` and `NewVolume` resources are associated with the `CreateProdResources` condition so that the resources are created only if the condition evaluates to true.
In this example, you can create an Amazon RDS DB instance from a snapshot. If you specify the `DBSnapshotName` parameter, AWS CloudFormation uses the parameter value as the snapshot name when creating the DB instance. If you keep the default value (empty string), AWS CloudFormation removes the `DBSnapshotIdentifier` property and creates a DB instance from scratch.
The example defines the `DBUser` and `DBPassword` parameters with their `NoEcho` property set to `true`. If you set the `NoEcho` attribute to `true`, CloudFormation returns the parameter value masked as asterisks (*****) for any calls that describe the stack or stack events, except for information stored in the locations specified below.
Using the `NoEcho` attribute does not mask any information stored in the following:
The `Metadata` template section. CloudFormation does not transform, modify, or redact any information you include in the `Metadata` section. For more information, see Metadata.
The `Outputs` template section. For more information, see Outputs.
The `Metadata` attribute of a resource definition. For more information, Metadata attribute.
We strongly recommend you do not use these mechanisms to include sensitive information, such as passwords or secrets.
Rather than embedding sensitive information directly in your AWS CloudFormation templates, we recommend you use dynamic parameters in the stack template to reference sensitive information that is stored and managed outside of CloudFormation, such as in the AWS Systems Manager Parameter Store or AWS Secrets Manager.
For more information, see the Do not embed credentials in your templates best practice.
Do not embed credentials in your templates
{
"AWSTemplateFormatVersion" : "2010-09-09",
"Parameters": {
"DBUser": {
"NoEcho": "true",
"Description" : "The database admin account username",
"Type": "String",
"MinLength": "1",
"MaxLength": "16",
"AllowedPattern" : "[a-zA-Z][a-zA-Z0-9]*",
"ConstraintDescription" : "must begin with a letter and contain only alphanumeric characters."
},
"DBPassword": {
"NoEcho": "true",
"Description" : "The database admin account password",
"Type": "String",
"MinLength": "1",
"MaxLength": "41",
"AllowedPattern" : "[a-zA-Z0-9]*",
"ConstraintDescription" : "must contain only alphanumeric characters."
},
"DBSnapshotName": {
"Description": "The name of a DB snapshot (optional)",
"Default": "",
"Type": "String"
}
},
"Conditions": {
"UseDBSnapshot": {"Fn::Not": [{"Fn::Equals" : [{"Ref" : "DBSnapshotName"}, ""]}]}
},
"Resources" : {
"MyDB" : {
"Type" : "AWS::RDS::DBInstance",
"Properties" : {
"AllocatedStorage" : "5",
"DBInstanceClass" : "db.t2.small",
"Engine" : "MySQL",
"EngineVersion" : "5.5",
"MasterUsername" : { "Ref" : "DBUser" },
"MasterUserPassword" : { "Ref" : "DBPassword" },
"DBParameterGroupName" : { "Ref" : "MyRDSParamGroup" },
"DBSnapshotIdentifier" : {
"Fn::If" : [
"UseDBSnapshot",
{"Ref" : "DBSnapshotName"},
{"Ref" : "AWS::NoValue"}
]
}
}
},
"MyRDSParamGroup" : {
"Type": "AWS::RDS::DBParameterGroup",
"Properties" : {
"Family" : "MySQL5.5",
"Description" : "CloudFormation Sample Database Parameter Group",
"Parameters" : {
"autocommit" : "1" ,
"general_log" : "1",
"old_passwords" : "0"
}
}
}
}
}
AWSTemplateFormatVersion: "2010-09-09"
Parameters:
DBUser:
NoEcho: true
Description: The database admin account username
Type: String
MinLength: 1
MaxLength: 16
AllowedPattern: "[a-zA-Z][a-zA-Z0-9]*"
ConstraintDescription: must begin with a letter and contain only alphanumeric characters.
DBPassword:
NoEcho: true
Description: The database admin account password
Type: String
MinLength: 1
MaxLength: 41
AllowedPattern: "[a-zA-Z0-9]*"
ConstraintDescription: must contain only alphanumeric characters.
DBSnapshotName:
Description: The name of a DB snapshot (optional)
Default: ""
Type: String
Conditions:
UseDBSnapshot: !Not [!Equals [!Ref DBSnapshotName, ""]]
Resources:
MyDB:
Type: "AWS::RDS::DBInstance"
Properties:
AllocatedStorage: 5
DBInstanceClass: db.t2.small
Engine: MySQL
EngineVersion: 5.5
MasterUsername: !Ref DBUser
MasterUserPassword: !Ref DBPassword
DBParameterGroupName: !Ref MyRDSParamGroup
DBSnapshotIdentifier: !If [UseDBSnapshot, !Ref DBSnapshotName, !Ref "AWS::NoValue"]
MyRDSParamGroup:
Type: "AWS::RDS::DBParameterGroup"
Properties:
Family: MySQL5.5
Description: CloudFormation Sample Database Parameter Group
Parameters:
autocommit: 1
general_log: 1
old_passwords: 0
The `UseDBSnapshot` condition evaluates to true only if the `DBSnapshotName` is not an empty string. If the `UseDBSnapshot` condition evaluates to true, AWS CloudFormation uses the `DBSnapshotName` parameter value for the `DBSnapshotIdentifier` property. If the condition evaluates to false, AWS CloudFormation removes the `DBSnapshotIdentifier` property. The `AWS::NoValue` pseudo parameter removes the corresponding resource property when it is used as a return value.
In this example, you can use an Amazon EC2 security group that has already been created or you can create a new security group, which is specified in the template. For the `ExistingSecurityGroup` parameter, you can specify the `default` security group name or `NONE`. If you specify `default`, AWS CloudFormation uses a security group that has already been created and is named `default`. If you specify `NONE`, AWS CloudFormation creates the security group that's defined in the template.
{
"Parameters" : {
"ExistingSecurityGroup" : {
"Description" : "An existing security group ID (optional).",
"Default" : "NONE",
"Type" : "String",
"AllowedValues" : ["default", "NONE"]
}
},
"Conditions" : {
"CreateNewSecurityGroup" : {"Fn::Equals" : [{"Ref" : "ExistingSecurityGroup"}, "NONE"] }
},
"Resources" : {
"MyInstance" : {
"Type" : "AWS::EC2::Instance",
"Properties" : {
"ImageId" : "ami-0ff8a91507f77f867",
"SecurityGroups" : [{
"Fn::If" : [
"CreateNewSecurityGroup",
{"Ref" : "NewSecurityGroup"},
{"Ref" : "ExistingSecurityGroup"}
]
}]
}
},
"NewSecurityGroup" : {
"Type" : "AWS::EC2::SecurityGroup",
"Condition" : "CreateNewSecurityGroup",
"Properties" : {
"GroupDescription" : "Enable HTTP access via port 80",
"SecurityGroupIngress" : [ {
"IpProtocol" : "tcp",
"FromPort" : "80",
"ToPort" : "80",
"CidrIp" : "0.0.0.0/0"
} ]
}
}
},
"Outputs" : {
"SecurityGroupId" : {
"Description" : "Group ID of the security group used.",
"Value" : {
"Fn::If" : [
"CreateNewSecurityGroup",
{"Ref" : "NewSecurityGroup"},
{"Ref" : "ExistingSecurityGroup"}
]
}
}
}
}
Parameters:
ExistingSecurityGroup:
Description: An existing security group ID (optional).
Default: NONE
Type: String
AllowedValues:
- default
- NONE
Conditions:
CreateNewSecurityGroup: !Equals [!Ref ExistingSecurityGroup, NONE]
Resources:
MyInstance:
Type: "AWS::EC2::Instance"
Properties:
ImageId: "ami-0ff8a91507f77f867"
SecurityGroups: !If [CreateNewSecurityGroup, !Ref NewSecurityGroup, !Ref ExistingSecurityGroup]
NewSecurityGroup:
Type: "AWS::EC2::SecurityGroup"
Condition: CreateNewSecurityGroup
Properties:
GroupDescription: Enable HTTP access via port 80
SecurityGroupIngress:
-
IpProtocol: tcp
FromPort: 80
ToPort: 80
CidrIp: 0.0.0.0/0
Outputs:
SecurityGroupId:
Description: Group ID of the security group used.
Value: !If [CreateNewSecurityGroup, !Ref NewSecurityGroup, !Ref ExistingSecurityGroup]
To determine whether to create the `NewSecurityGroup` resource, the resource is associated with the `CreateNewSecurityGroup` condition. The resource is created only when the condition is true (when the `ExistingSecurityGroup` parameter is equal to `NONE`).
In the `SecurityGroups` property, the template uses the `Fn::If` intrinsic function to determine which security group to use. If the `CreateNewSecurityGroup` condition evaluates to true, the security group property references the `NewSecurityGroup` resource. If the `CreateNewSecurityGroup` condition evaluates to false, the security group property references the `ExistingSecurityGroup` parameter (the `default` security group).
Lastly, the template conditionally outputs the security group ID. If the `CreateNewSecurityGroup` condition evaluates to true, AWS CloudFormation outputs the security group ID of the `NewSecurityGroup` resource. If the condition is false, AWS CloudFormation outputs the security group ID of the `ExistingSecurityGroup` resource.