tvl-depot/fun/quinistry

Quinistry

A simple Docker registry quine.

What?

This is an example project for a from-scratch implementation of an HTTP server compatible with the Docker Registry V2 protocol.

It serves a single image called quinistry:latest which is a Docker image that runs quinistry itself, therefore it is a sort of Docker registry quine.

The official documentation does not contain enough information to actually implement this protocol (which I assume is intentional), but a bit of trial&error lead there anyways. I've added comments to parts of the code to clear up things that may be helpful to other developers in the future.

Example

# Run quinistry:
vincent@urdhva ~/go/src/github.com/tazjin/quinistry (git)-[master] % ./quinistry
2017/03/16 14:11:56 Starting quinistry

# Pull the quinistry image from itself:
vincent@urdhva ~ % docker pull localhost:8080/quinistry
Using default tag: latest
latest: Pulling from quinistry
7bf1a8b18466: Already exists
Digest: sha256:d5cd4490901ef04b4e28e4ccc03a1d25fe3461200cf4d7166aab86fcd495e22e
Status: Downloaded newer image for localhost:8080/quinistry:latest

# Quinistry will log:
2017/03/16 14:14:03 Acknowleding V2 API: GET /v2/
2017/03/16 14:14:03 Serving manifest: GET /v2/quinistry/manifests/latest
2017/03/16 14:14:03 Serving config: GET /v2/quinistry/blobs/sha256:fbb165c48849de16017aa398aa9bb08fd1c00eaa7c150b6c2af37312913db279

# Run the downloaded image:
vincent@urdhva ~ % docker run -p 8090:8080 localhost:8080/quinistry
2017/03/16 13:15:18 Starting quinistry

# And download it again from itself:
vincent@urdhva ~ % docker pull localhost:8090/quinistry
Using default tag: latest
latest: Pulling from quinistry
7bf1a8b18466: Already exists
Digest: sha256:11141d95ddce0bac9ffa32ab1e8bc94748ed923e87762c68858dc41d11a46d3f
Status: Downloaded newer image for localhost:8090/quinistry:latest

Building

Quinistry creates a Docker image that only contains a statically linked main binary. As this package makes use of net/http, Go will (by default) link against libc for DNS resolution and create a dynamic binary instead.

To disable this, build the project with -tags netgo:

go build -tags netgo