Get Docker Alternate Tags for a Docker Image

[Stephen.Schaff]

Kubernetes has an issue where if you use the latest tag, it sometimes will not pull the image, even when it has changed. So I am trying to write a script that will get a different, more unique tag, for use in my helm charts.

The standard Docker REST API does not have anything that can do in in a reasonable number of calls. (You have to get a list of ALL the tags, and then iterate through them one at a time looking to see which ones have a digest that matches the "latest" tag.)

I am wondering if ProGet has something better built into it. Does ProGet have a way to get the other tags on a Docker Image?

Basically, I am looking for the list of tags found on this page:

Except that I would start with the latest tag and end up with the 1.0.9 tag as the result.

[rhessinger]

Hi @Stephen-Schaff,

The latest tag is a bit odd. Each client handles it differently and I have found most clients will not repull a newer version if latest has already been pulled once. According to Docker's API (and Kubernetes), a client is supposed to pull the manifest from the server and compare it with the currently downloaded image and update if there is any difference, but I have found that does not always work. You can configure Kubernetes to always pull an image, but I cannot confirm how well it works.

As for getting a list of tags, we basically have two ways.

What it sounds like you are looking for is to just get a list of alternative tags. The only way to do this is to use our native API and using the DockerImages_GetTags method and grouping by DockerImage_Id.

The other way to get a list of tags would be to use the docker API itself. This way will get all tags associated with a repository, not just the alternative tags. To do this:

1. Make a get request to http://<your proget server>/v2/_auth with an Authorization header with the value of Basic <BASE 64 encoded username:password>
2. The response will be a JSON object. Take the value in the token property
3. Make a GET request to list all tags to http://<your proget server>/v2/<feed name>/<image>/tags/list (ex: `http://proget.localhost/v2/defaultdocker6/dotnet/core/aspnet/tags/list)
   1. In the header include an Authorization header with a value Bearer <token from step 1>
4. This will return a JSON object that has an array property called tags

That will get you a list of tags using the Docker API.

Hope this helps!

Thanks,
Rich