Add support for HTTP redirection for push and pull

[proppy]

So that storage driver can decide to redirect to vendor upload and serving static URLs instead of serving the content dynamically.

[samalba]

:+1:

Apparently Docker follows the redirections, so it'll work out of the box if the Registry serves 302 for pulling the layers.

I'd make this optional in the config though since it's related to the storage backend being used.

[ghost]

Fantastic, I was about to ask this as well. Thank you!

[ghost]

Hello, Is this already available in the current release?

[samalba]

No, it's something that has been only discussed so far. But we accept pull requests :-)

[pwaller]

This feature is important to me, and should be important to you, too!

I want to run the registry on a puny machine so I don't have to pay much for that machine.

Currently, I host my images on S3. If I run the registry on a puny machine and launch several machines who simultaneously pull, I get a thundering herd which kills the puny machine. If the puny machine just did a HTTP 302 redirect to a pre-signed S3 URL, then it wouldn't have to have any data flowing through it except for the HTTP request. S3 can handle pushing the bytes to the server in a distributed manner, as S3 is good at.

[pwaller]

I can't see any way of pulling this off with the current StorageDriver interface. Is there any space to fit in the required interfaces for a HTTP-redirecting storage driver in docker-registry-ng?

[zmmwl]

@samalba Is this available now? I still can't get redirection yet.