README.md

imageDependency

A Lambda function which implements a Custom Resource for Cloud Formation that gets an Image (AMI) by name.

Installation

Create a Role with ./create-role.sh. This creates a new stack with the appropriate permissions for the function.

Deploy the lambda function with ./deploy-lambda.sh. Now the function can be used to get Images via a Cloud Formation Custom Resource.

Cloud Formation Usage

Use the function inside your Cloud Formation template by declaring a custom resource, Custom::ImageDependency.

The Custom::ImageDependency refers to a ImageName that is sent to the Lambda function and is used to lookup the Image. If no Image or more than one is found FAILED is returned.

The outputs from the Custom::ImageDependency can be referred with Fn:GetAtt.

Available values are: ImageId, CreationDate, ...

Example: "Fn::GetAtt": ["Image", "ImageId"]

Example Output

{
  ImageId: 'ami-cd4f25ba',
  ImageLocation: '143044406720/docker image 201505121634',
  State: 'available',
  OwnerId: '143044406720',
  CreationDate: '2015-05-12T14:34:36.000Z',
  Public: false,
  Architecture: 'x86_64',
  ImageType: 'machine',
  SriovNetSupport: 'simple',
  Name: 'docker image 201505121634',
  RootDeviceType: 'ebs',
  RootDeviceName: '/dev/xvda',
  VirtualizationType: 'hvm',
  Tags: '',
  Hypervisor: 'xen'
}

Extended Example with Stack

"Parameters": {
  "ImageName": {
    "Description": "Name of the Image",
    "Type": "String",
    "Default": "default"
  }
},
"Resources": {
  "Image": {
    "Type": "Custom::ImageDependency",
    "Properties": {
      "ServiceToken": { "Fn::Join": [ "", [
        "arn:aws:lambda:",
        { "Ref": "AWS::Region" },
        ":",
        { "Ref": "AWS::AccountId" },
        ":function:imageDependency"
      ] ] },
      "ImageName": { "Ref": "ImageName" }
    }
  }
  "Outputs": {
    "ImageId": {
      "Value": {
        "Fn::GetAtt": [ "Image", "ImageId" ]
      },
      "Description": "Image Id"
    }
  }
}