AWS Documentation » Amazon ECR » User Guide » Images » Amazon ECR Lifecycle Policies

Amazon ECR Lifecycle Policies

Amazon ECR lifecycle policies enable you to specify the lifecycle management of images in a repository. A lifecycle policy is a set of one or more rules, where each rule defines an action for Amazon ECR. The actions apply to images that contain tags prefixed with the given strings. This allows the automation of cleaning up unused images, for example expiring images based on age or count. You should expect that after creating a lifecycle policy the affected images are expired within 24 hours.

Topics

• Lifecycle Policy Template
• Lifecycle Policy Parameters
• Lifecycle Policy Evaluation Rules
• Creating a Lifecycle Policy Preview
• Creating a Lifecycle Policy
• Examples of Lifecycle Policies

Lifecycle Policy Template

The contents of your lifecycle policy is evaluated before being associated with a repository. The following is the JSON syntax template for the lifecycle policy. For lifecycle policy examples, see Examples of Lifecycle Policies.

{
    "rules": [
        {
            "rulePriority": integer,
            "description": "string",
            "selection": {
                "tagStatus": "tagged"|"untagged"|"any",
                "tagPrefixList": list<string>,
                "countType": "imageCountMoreThan"|"sinceImagePushed",
                "countUnit": "string",
                "countNumber": integer
            },
            "action": {
                "type": "expire"
            }
        }
    ]
}

Note

The tagPrefixList parameter is only used if tagStatus is tagged. The countUnit parameter is only used if countType is sinceImagePushed. The countNumber parameter is only used if countType is set to imageCountMoreThan.

Lifecycle Policy Parameters

Lifecycle policies are split into the following parts:

Rule Priority

rulePriority

Type: integer

Required: yes

Sets the order in which rules are evaluated, lowest to highest. When you add rules to a lifecycle policy, you must give them each a unique value for rulePriority. Values do not need to be sequential across rules in a policy. A rule with a tagStatus value of any must have the highest value for rulePriority and be evaluated last.

Description

description

Type: string

Required: no

(Optional) Describes the purpose of a rule within a lifecycle policy.

Tag Status

tagStatus

Type: string

Required: yes

Determines whether the lifecycle policy rule that you are adding specifies a tag for an image. Acceptable options are tagged, untagged, or any. If you specify any, then all images have the rule applied to them. If you specify tagged, then you must also specify a tagPrefixList value. If you specify untagged, then you must omit tagPrefixList.

Tag Prefix List

tagPrefixList

Type: list[string]

Required: yes, only if tagStatus is set to tagged

Only used if you specified "tagStatus": "tagged". You must specify a comma-separated list of image tag prefixes on which to take action with your lifecycle policy. For example, if your images are tagged as prod, prod1, prod2, and so on, you would use the tag prefix prod to specify all of them. If you specify multiple tags, only the images with all specified tags are selected.

Count Type

countType

Type: string

Required: yes

Specify a count type to apply to the images. If countType is set to imageCountMoreThan, you also specify countNumber to create a rule that sets a limit on the number of images that exist in your repository. If countType is set to sinceImagePushed, you also specify countUnit and countNumber to specify a time limit on the images that exist in your repository.

Count Unit

countUnit

Type: string

Required: yes, only if countType is set to sinceImagePushed

Specify a count unit of days to indicate that as the unit of time, in addition to countNumber, which is the number of days.

Count Number

countNumber

Type: integer

Required: yes

Specify a count number. If the countType used is imageCountMoreThan, then the value is the maximum number of images that you want to retain in your repository. If the countType used is sinceImagePushed, then the value is the maximum age limit for your images.

Action

type

Type: string

Required: yes

Specify an action type. The supported value is expire.

Lifecycle Policy Evaluation Rules

The lifecycle policy evaluator is responsible for parsing the plaintext JSON and applying it to the images in the specified repository. The following rules should be noted when creating a lifecycle policy:

• An image is expired by exactly one or zero rules.

• An image that matches the tagging requirements of a rule cannot be expired by a rule with a lower priority.

• Rules can never mark images that are marked by higher priority rules, but can still identify them as if they haven't been expired.

• The set of rules must contain a unique set of tag prefixes.

• Only one rule is allowed to select untagged images.

• Expiration is always ordered by pushed_at_time, and always expires older images before newer ones.

• When using the tagPrefixList, an image is successfully matched if all of the tags in the tagPrefixList value are matched against any of the image's tags.

• With countType = imageCountMoreThan, images are sorted from youngest to oldest based on pushed_at_time and then all images greater than the specified count are expired.

• With countType = sinceImagePushed, all images whose pushed_at_time is older than the specified number of days based on countNumber are expired.