Amazon CloudFormation template snippets - Amazon CloudFormation
Nested stacksWait condition
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Amazon CloudFormation template snippets

Nested stacks

Nesting a stack in a template

This example template contains a nested stack resource called myStack. When Amazon CloudFormation creates a stack from the template, it creates the myStack, whose template is specified in the TemplateURL property. The output value StackRef returns the stack ID for myStack and the value OutputFromNestedStack returns the output value BucketName from within the myStack resource. The Outputs.nestedstackoutputname format is reserved for specifying output values from nested stacks and can be used anywhere within the containing template.

For more information, see AWS::CloudFormation::Stack.

JSON

{
    "AWSTemplateFormatVersion" : "2010-09-09",
    "Resources" : {
        "myStack" : {
	       "Type" : "AWS::CloudFormation::Stack",
	       "Properties" : {
	        "TemplateURL" : "https://s3.amazonaws.com/cloudformation-templates-us-east-1/S3_Bucket.template",
              "TimeoutInMinutes" : "60"
	       }
        }
    },
    "Outputs": {
       "StackRef": {"Value": { "Ref" : "myStack"}},
       "OutputFromNestedStack" : {
             "Value" : { "Fn::GetAtt" : [ "myStack", "Outputs.BucketName" ] }
       }
    }
}

YAML

AWSTemplateFormatVersion: '2010-09-09'
Resources:
  myStack:
    Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: https://s3.amazonaws.com/cloudformation-templates-us-east-1/S3_Bucket.template
      TimeoutInMinutes: '60'
Outputs:
  StackRef:
    Value: !Ref myStack
  OutputFromNestedStack:
    Value: !GetAtt myStack.Outputs.BucketName

Nesting a stack with input parameters in a template

This example template contains a stack resource that specifies input parameters. When Amazon CloudFormation creates a stack from this template, it uses the value pairs declared within the Parameters property as the input parameters for the template used to create the myStackWithParams stack. In this example, the InstanceType and KeyName parameters are specified.

For more information, see AWS::CloudFormation::Stack.

JSON

{
    "AWSTemplateFormatVersion" : "2010-09-09",
    "Resources" : {
        "myStackWithParams" : {
  	       "Type" : "AWS::CloudFormation::Stack",
	       "Properties" : {
	           "TemplateURL" : "https://s3.amazonaws.com/cloudformation-templates-us-east-1/EC2ChooseAMI.template",
	           "Parameters" : {
	               "InstanceType" : "t2.micro",
	               "KeyName" : "mykey"
	           }
   	       }
        }
    }
}

YAML

AWSTemplateFormatVersion: '2010-09-09'
Resources:
  myStackWithParams:
    Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: https://s3.amazonaws.com/cloudformation-templates-us-east-1/EC2ChooseAMI.template
      Parameters:
        InstanceType: t2.micro
        KeyName: mykey

Wait condition

Using a wait condition with an Amazon EC2 instance

Important

For Amazon EC2 and Auto Scaling resources, we recommend that you use a CreationPolicy attribute instead of wait conditions. Add a CreationPolicy attribute to those resources, and use the cfn-signal helper script to signal when an instance creation process has completed successfully.

If you can't use a creation policy, you view the following example template, which declares an Amazon EC2 instance with a wait condition. The wait condition myWaitCondition uses myWaitConditionHandle for signaling, uses the DependsOn attribute to specify that the wait condition will trigger after the Amazon EC2 instance resource has been created, and uses the Timeout property to specify a duration of 4500 seconds for the wait condition. In addition, the presigned URL that signals the wait condition is passed to the Amazon EC2 instance with the UserData property of the Ec2Instance resource, thus enabling an application or script running on that Amazon EC2 instance to retrieve the presigned URL and employ it to signal a success or failure to the wait condition. You need to use cfn-signal or create the application or script that signals the wait condition. The output value ApplicationData contains the data passed back from the wait condition signal.

For more information, see Creating wait conditions in a template, AWS::CloudFormation::WaitCondition, AWS::CloudFormation::WaitConditionHandle, and cfn-signal.

JSON

{
    "AWSTemplateFormatVersion" : "2010-09-09",
    "Mappings" : {
        "RegionMap" : {
            "us-east-1" : {
                "AMI" : "ami-0ff8a91507f77f867"
            },
            "us-west-1" : {
                "AMI" : "ami-0bdb828fd58c52235"
            },
            "eu-west-1" : {
                "AMI" : "ami-047bb4163c506cd98"
            },
            "ap-northeast-1" : {
                "AMI" : "ami-06cd52961ce9f0d85"
            },
            "ap-southeast-1" : {
                "AMI" : "ami-08569b978cc4dfa10"
            }
        }
    },
    "Resources" : {
        "Ec2Instance" : {
            "Type" : "AWS::EC2::Instance",
            "Properties" : {
                "UserData" : { "Fn::Base64" : {"Ref" : "myWaitHandle"}},
                "ImageId" : { "Fn::FindInMap" : [ "RegionMap", { "Ref" : "AWS::Region" }, "AMI" ]}
            }
        },
        "myWaitHandle" : {
            "Type" : "AWS::CloudFormation::WaitConditionHandle",
            "Properties" : {
            }
        },
        "myWaitCondition" : {
            "Type" : "AWS::CloudFormation::WaitCondition",
            "DependsOn" : "Ec2Instance",
            "Properties" : {
                "Handle" : { "Ref" : "myWaitHandle" },
                "Timeout" : "4500"
            }
        }
    },
    "Outputs" : {
        "ApplicationData" : {
            "Value" : { "Fn::GetAtt" : [ "myWaitCondition", "Data" ]},
            "Description" : "The data passed back as part of signalling the WaitCondition."
        }
    }
}

YAML

AWSTemplateFormatVersion: '2010-09-09'
Mappings:
  RegionMap:
    us-east-1:
      AMI: ami-0ff8a91507f77f867
    us-west-1:
      AMI: ami-0bdb828fd58c52235
    eu-west-1:
      AMI: ami-047bb4163c506cd98
    ap-northeast-1:
      AMI: ami-06cd52961ce9f0d85
    ap-southeast-1:
      AMI: ami-08569b978cc4dfa10
Resources:
  Ec2Instance:
    Type: AWS::EC2::Instance
    Properties:
      UserData:
        Fn::Base64: !Ref myWaitHandle
      ImageId:
        Fn::FindInMap:
        - RegionMap
        - Ref: AWS::Region
        - AMI
  myWaitHandle:
    Type: AWS::CloudFormation::WaitConditionHandle
    Properties: {}
  myWaitCondition:
    Type: AWS::CloudFormation::WaitCondition
    DependsOn: Ec2Instance
    Properties:
      Handle: !Ref myWaitHandle
      Timeout: '4500'
Outputs:
  ApplicationData:
    Value: !GetAtt myWaitCondition.Data
    Description: The data passed back as part of signalling the WaitCondition.

Using the cfn-signal helper script to signal a wait condition

This example shows a cfn-signal command line that signals success to a wait condition. You need to define the command line in the UserData property of the EC2 instance.

JSON

"UserData": {
  "Fn::Base64": {
    "Fn::Join": [
      "", 
      [
         "#!/bin/bash -xe\n",
         "/opt/aws/bin/cfn-signal --exit-code 0 '", 
         {
           "Ref": "myWaitHandle"
         },
         "'\n"
      ]   
    ]
  }
}

YAML

UserData:
  'Fn::Base64':
    'Fn::Join':
      - ''
      - - |
          #!/bin/bash -xe
        - /opt/aws/bin/cfn-signal --exit-code 0 '
        - Ref: myWaitHandle
        - |
          '

Using Curl to signal a wait condition

This example shows a Curl command line that signals success to a wait condition.

curl -T /tmp/a "https://cloudformation-waitcondition-test.s3.amazonaws.com/arn%3Aaws%3Acloudformation%3Aus-east-1%3A034017226601%3Astack%2Fstack-gosar-20110427004224-test-stack-with-WaitCondition--VEYW%2Fe498ce60-70a1-11e0-81a7-5081d0136786%2FmyWaitConditionHandle?Expires=1303976584&AWSAccessKeyId=AKIAIOSFODNN7EXAMPLE&Signature=ik1twT6hpS4cgNAw7wyOoRejVoo%3D"

Where the file /tmp/a contains the following JSON structure:

{
  "Status" : "SUCCESS",
  "Reason" : "Configuration Complete",
  "UniqueId" : "ID1234",
  "Data" : "Application has completed configuration."
}

This example shows a Curl command line that sends the same success signal except it sends the JSON as a parameter on the command line.

curl -X PUT -H 'Content-Type:' --data-binary '{"Status" : "SUCCESS","Reason" : "Configuration Complete","UniqueId" : "ID1234","Data" : "Application has completed configuration."}' "https://cloudformation-waitcondition-test.s3.amazonaws.com/arn%3Aaws%3Acloudformation%3Aus-east-1%3A034017226601%3Astack%2Fstack-gosar-20110427004224-test-stack-with-WaitCondition--VEYW%2Fe498ce60-70a1-11e0-81a7-5081d0136786%2FmyWaitConditionHandle?Expires=1303976584&AWSAccessKeyId=AKIAIOSFODNN7EXAMPLE&Signature=ik1twT6hpS4cgNAw7wyOoRejVoo%3D"