google container registry pull through cache

Question

I setup docker daemon to use https://mirror.gcr.io as a registry mirror following this guide.

In the doc, they say this

Container Registry adds frequently requested images to the cache so they are available for future requests. It also periodically removes images that are no longer requested.

Is this mirror registry just acting as a cache for some of the popular images from Docker Hub, or can it act as a cache for my own images in Docker Hub?

Answer 1

Based on the Pulling cached images section of the Pulling cached images doc

Container Registry adds frequently requested images to the cache so they are available for future requests. It also periodically removes images that are no longer requested.

This contemplates also your own images and not only public images from Docker Hub.

Looking at the daemon setup on the documentation it can be used as cache for your images because those images are in Docker Hub, not another private registry.

Please check this other answer as reference.

Answer 2

My understanding is you might be looking for something like a true "pull through cache" (e.g., what ECR has). This is unsupported as far as I can tell.

• There is a way to set a login for DockerHub but that seems mostly related to rate limits. This should work if you just want things to be in Artifact Registry, but seems more global to all of DockerHub.

• And there is an option for migrating from a third party registry, but this is not a cache either, rather a one time copy...

There are no options for a true "pull through cache" for your own images from what I can see. Their docs for their mirror say "frequently accessed public images", which if your images are private OR are not accessed by a large volume of users, I suspect they will not show up there.