问题
I'm working on a simple REST client for Docker Registry. For private registries, name resolution is pretty simple; if the image name is myregistry.io/myimage:latest
, I look for https://myregistry.io/v2
and query the API there.
However, I notice that for docker hub, it doesn't quite work that way. If I'm looking for ubuntu
, I can expand that to docker.io/ubuntu:latest
, but https://docker.io/v2
returns a 307 redirect to https://www.docker.com/v2
, which just returns HTML. The actual registry endpoint is at https://registry-1.docker.io/v2
.
Is this just a hardcoded special case in the docker client, or is there some extra logic to looking up registry endpoints that I'm unaware of? If it is just a special case, is there more to it than always going to registry-1.docker.io
instead of docker.io
?
回答1:
The central Docker registry is a well-known special case, similar to Maven central. You can see the defaults e.g. at https://github.com/docker/docker-ce/blob/ea449e9b10cebb259e1a43325587cd9a0e98d0ff/components/engine/registry/config.go#L42:
var (
// DefaultNamespace is the default namespace
DefaultNamespace = "docker.io"
// DefaultRegistryVersionHeader is the name of the default HTTP header
// that carries Registry version info
DefaultRegistryVersionHeader = "Docker-Distribution-Api-Version"
// IndexHostname is the index hostname
IndexHostname = "index.docker.io"
// IndexServer is used for user auth and image search
IndexServer = "https://" + IndexHostname + "/v1/"
// IndexName is the name of the index
IndexName = "docker.io"
// DefaultV2Registry is the URI of the default v2 registry
DefaultV2Registry = &url.URL{
Scheme: "https",
Host: "registry-1.docker.io",
}
)
来源:https://stackoverflow.com/questions/49455033/docker-registry-name-resolution