Sync an upstream registry with an Amazon ECR private registry - Amazon ECR

Sync an upstream registry with an Amazon ECR private registry

Using pull through cache rules, you can sync the contents of an upstream registry with your Amazon ECR private registry.

Amazon ECR currently supports creating pull through cache rules for the following upstream registries.

  • Docker Hub, Microsoft Azure Container Registry, GitHub Container Registry, and GitLab Container Registry (Requires authentication)

  • Amazon ECR Public, the Kubernetes container image registry, and Quay (Doesn't require authentication)

For GitLab Container Registry, Amazon ECR supports pull through cache only with GitLab software-as-a-service offering, GitLab.com.

For the upstream registries that require authentication, you must store your credentials in an AWS Secrets Manager secret. The Amazon ECR console makes it easy for you to create the Secrets Manager secret for each of the authenticated upstream registries. For more information about creating a Secrets Manager secret using the Secrets Manager console, see Storing your upstream repository credentials in an AWS Secrets Manager secret.

After you've created a pull through cache rule for the upstream registry, simply pull an image from that upstream registry using your Amazon ECR private registry URI. Amazon ECR then creates a repository and caches that image in your private registry. On your subsequent pull requests of the cached image with a given tag, Amazon ECR checks the upstream registry to see if there is a new version of the image with that specific tag and attempts to update the image in your private registry at least once every 24 hours.

Repository creation templates

Amazon ECR has added support for repository creation templates, currently in preview, which gives you the control to specify initial configurations for new repositories created by Amazon ECR on your behalf using pull through cache rules. Each template contains a repository namespace prefix which is used to match new repositories to a specific template. Templates can specify the configuration for all repository settings including resource-based access policies, tag immutability, encryption, and lifecycle policies. The settings in a repository creation template are only applied during repository creation and don't have any effect on existing repositories or repositories created using any other method. For more information, see Templates to control repositories created during a pull through cache action.

Considerations for using pull through cache rules

Consider the following when using Amazon ECR pull through cache rules.

  • Creating pull through cache rules isn't supported in the following Regions.

    • China (Beijing) (cn-north-1)

    • China (Ningxia) (cn-northwest-1)

    • AWS GovCloud (US-East) (us-gov-east-1)

    • AWS GovCloud (US-West) (us-gov-west-1)

  • AWS Lambda doesn't support pulling container images from Amazon ECR using a pull through cache rule.

  • When pulling images using pull through cache, the Amazon ECR FIPS service endpoints aren't supported the first time an image is pulled. Using the Amazon ECR FIPS service endpoints work on subsequent pulls though.

  • When a cached image is pulled through the Amazon ECR private registry URI, the image pulls are initiated by AWS IP addresses. This ensures that the image pull doesn't count against any pull rate quotas implemented by the upstream registry.

  • When a cached image is pulled through the Amazon ECR private registry URI, Amazon ECR checks the upstream repository at least once every 24 hours to verify whether the cached image is the latest version. If there is a newer image in the upstream registry, Amazon ECR attempts to update the cached image. This timer is based off the last pull of the cached image.

  • If Amazon ECR is unable to update the image from the upstream registry for any reason and the image is pulled, the last cached image will still be pulled.

  • When creating the Secrets Manager secret that contains the upstream registry credentials, the secret name must use the ecr-pullthroughcache/ prefix. The secret must also be in the same account and Region that the pull through cache rule is created in.

  • When a multi-architecture image is pulled using a pull through cache rule, the manifest list and each image referenced in the manifest list are pulled to the Amazon ECR repository. If you only want to pull a specific architecture, you can pull the image using the image digest or tag associated with the architecture rather than the tag associated with the manifest list.

  • Amazon ECR uses a service-linked IAM role, which provides the permissions needed for Amazon ECR to create the repository, retrieve the Secrets Manager secret value for authentication, and push the cached image on your behalf. The service-linked IAM role is created automatically when a pull through cache rule is created. For more information, see Amazon ECR service-linked role for pull through cache.

  • By default, the IAM principal pulling the cached image has the permissions granted to them through their IAM policy. You may use the Amazon ECR private registry permissions policy to further scope the permissions of an IAM entity. For more information, see Using registry permissions.

  • Amazon ECR repositories created using the pull through cache workflow are treated like any other Amazon ECR repository. All repository features, such as replication and image scanning are supported.

  • When Amazon ECR creates a new repository on your behalf using a pull through cache action, the following default settings are applied to the repository unless there is a matching repository creation template. You can use a repository creation template to define the settings applied to repositories created by Amazon ECR on your behalf. For more information, see Templates to control repositories created during a pull through cache action.

    • Tag immutability — Turned off, tags are mutable and can be overwritten.

    • Encryption — The default AES256 encryption is used.

    • Repository permissions — Omitted, no repository permissions policy is applied.

    • Lifecycle policy — Omitted, no lifecycle policy is applied.

    • Resource tags — Omitted, no resource tags are applied.

  • Turning on image tag immutability for repositories using a pull through cache rule will prevent Amazon ECR from updating images using the same tag.

  • When an image is pulled using the pull through cache rule for the first time a route to the internet may be required. There are certain circumstances in which a route to the internet is required so it's best to set up a route to avoid any failures. Thus, if you've configured Amazon ECR to use an interface VPC endpoint using AWS PrivateLink then you need to ensure the first pull has a route to the internet. One way to do this is to create a public subnet in the same VPC, with an internet gateway, and then route all outbound traffic to the internet from their private subnet to the public subnet. Subsequent image pulls using the pull through cache rule don't require this. For more information, see Example routing options in the Amazon Virtual Private Cloud User Guide.