How to define an ECR Lifecycle Policy with CloudFormation - aws-cloudformation

Question

In order to limit the number of images in a repository, I'd like to define a Lifecycle policy. Since all the stack is defined with CloudFormation, I'd like to define this policy too.
For example, my policy could be "keep only the most recent 8 images, no matter if tagged or not".

Answer 1

The solution was pretty easy, but since I could not find any example or similar questions (ECR is not mainstream, I know), let me post here the easy solution that I found, which simply requires to insert the policy as JSON into the CloudFormation definition:
MyRepository:
Type: AWS::ECR::Repository
Properties:
LifecyclePolicy:
LifecyclePolicyText: |
{
"rules": [
{
"rulePriority": 1,
"description": "Only keep 8 images",
"selection": {
"tagStatus": "any",
"countType": "imageCountMoreThan",
"countNumber": 8
},
"action": { "type": "expire" }
}]
}
Of course this is very simplistic, but it's the starting point that I was looking for

Answer 2

You can also define a reference to your PolicyText and later on your parameters.json stringify your policy.
It would look like something like this:
template.yml
Parameters:
lifecyclePolicyText:
Description: Lifecycle policy content (JSON), the policy content the pre-fixes for the microservices and the kind of policy (CountMoreThan).
Type: String
repositoryName:
Description: ECR Repository Name to which we will apply the lifecycle policies.
Type: String
registryId:
Description: AWS account identification number (12 digits)
Type: String
Default: xxxxx
Resources:
Repository:
Type: AWS::ECR::Repository
Properties:
LifecyclePolicy:
LifecyclePolicyText: !Ref lifecyclePolicyText
RegistryId: !Ref registryId
RepositoryName: !Ref repositoryName
Outputs:
Arn:
Value: !GetAtt Repository.Arn
parameters.json
[
{
"ParameterKey": "lifecyclePolicyText",
"ParameterValue": "{'rules':[{'rulePriority':1,'description':'Only keep 8 images','selection':{'tagStatus':'any','countType':'imageCountMoreThan','countNumber':8},'action':{'type':'expire'}}]}"
},
{
"ParameterKey": "repositoryName",
"ParameterValue": "xxxx"
}
]

Answer 3

| will allow you to add text inline.
AWSTemplateFormatVersion: "2010-09-09"
Resources:
ECRRepo:
Type: AWS::ECR::Repository
Properties:
RepositoryName: "images"
LifecyclePolicy:
LifecyclePolicyText: |
{
"rules": [
{
"rulePriority": 2,
"description": "Keep only one untagged image, expire all others",
"selection": {
"tagStatus": "untagged",
"countType": "imageCountMoreThan",
"countNumber": 1
},
"action": {
"type": "expire"
}
}
]
}