cfn-look-up-ami-ids

AWS Lambda blueprint to lookup AMI IDs by AMI Name

This blueprint mirrors the blueprint of the same name provide by AWS, with the following enhancements:

• Removes the restriction on looking up only AMI IDs owned by Amazon
• Uses a new parameter, AmiNameSearchString, as the match pattern against AMI Names. Previously, the pattern was hard-coded in the blueprint
• Improves error logging when the pattern does not match any images

Lambda Execution Role

Before creating the Lambda function, first create an IAM role with the following policy to use with this blueprint. For convenience, name the role something like cfn-look-up-ami-ids.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "logs:CreateLogGroup",
        "logs:CreateLogStream",
        "logs:PutLogEvents"
      ],
      "Resource": "arn:aws:logs:*:*:*"
    },
    {
      "Effect": "Allow",
      "Action": [ "ec2:DescribeImages" ],
      "Resource": "*"
    }
  ]
}

CloudFormation Example Usage

Use a CloudFormation Parameter to define the pattern to match against when searching for the AMI by Name. In the example below, the default value of the parameter AmiNameStringSearch is set to match the naming pattern Amazon uses for their Windows Server 2012 R2 AMIs.

  "Parameters" : {
    "AmiNameSearchString" : {
        "Description" : "Search pattern to match against an AMI Name",
        "Type" : "String",
        "Default" : "Windows_Server-2012-R2_RTM-English-64Bit-Base-*"
    }
  }

Call the Lambda function using a custom CloudFormation resource. This resource will return with an attribute named Id containing the AMI ID. Use the function Fn::GetAtt to reference this attribute within the ImageId property of the instance (or launch configuration).

  "Resources" : {
    "AmiIdLookup": {
      "Type": "Custom::AmiIdLookup",
      "Properties": {
        "ServiceToken": {
          "Fn::Join" : [
            ":",
            [
              "arn:aws:lambda",
              { "Ref" : "AWS::Region" },
              { "Ref" : "AWS::AccountId" },
              "function:cfn-look-up-ami-ids"
            ]
          ]
        },
        "Region": { "Ref" : "AWS::Region" },
        "AmiNameSearchString": { "Ref" : "AmiNameSearchString" }
      }
    },
    "MyInstance" :
    {
      "Type" : "AWS::EC2::Instance",
      "Properties" : {
        "ImageId": { "Fn::GetAtt": [ "AmiIdLookup", "Id" ] },
        # ... elided ...
      }
    }
  }