// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
// The nixery server implements a container registry that transparently builds
// container images based on Nix derivations.
//
// The Nix derivation used for image creation is responsible for creating
// objects that are compatible with the registry API. The targeted registry
// protocol is currently Docker's.
//
// When an image is requested, the required contents are parsed out of the
// request and a Nix-build is initiated that eventually responds with the
// manifest as well as information linking each layer digest to a local
// filesystem path.
package main
import (
"context"
"encoding/json"
"fmt"
"io/ioutil"
"net/http"
"regexp"
"github.com/google/nixery/server/builder"
"github.com/google/nixery/server/config"
"github.com/google/nixery/server/layers"
"github.com/google/nixery/server/storage"
log "github.com/sirupsen/logrus"
)
// ManifestMediaType is the Content-Type used for the manifest itself. This
// corresponds to the "Image Manifest V2, Schema 2" described on this page:
//
// https://docs.docker.com/registry/spec/manifest-v2-2/
const manifestMediaType string = "application/vnd.docker.distribution.manifest.v2+json"
// This variable will be initialised during the build process and set
// to the hash of the entire Nixery source tree.
var version string = "devel"
// Regexes matching the V2 Registry API routes. This only includes the
// routes required for serving images, since pushing and other such
// functionality is not available.
var (
manifestRegex = regexp.MustCompile(`^/v2/([\w|\-|\.|\_|\/]+)/manifests/([\w|\-|\.|\_]+)$`)
layerRegex = regexp.MustCompile(`^/v2/([\w|\-|\.|\_|\/]+)/blobs/sha256:(\w+)$`)
)
// Downloads the popularity information for the package set from the
// URL specified in Nixery's configuration.
func downloadPopularity(url string) (layers.Popularity, error) {
resp, err := http.Get(url)
if err != nil {
return nil, err
}
if resp.StatusCode != 200 {
return nil, fmt.Errorf("popularity download from '%s' returned status: %s\n", url, resp.Status)
}
j, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, err
}
var pop layers.Popularity
err = json.Unmarshal(j, &pop)
if err != nil {
return nil, err
}
return pop, nil
}
// Error format corresponding to the registry protocol V2 specification. This
// allows feeding back errors to clients in a way that can be presented to
// users.
type registryError struct {
Code string `json:"code"`
Message string `json:"message"`
}
type registryErrors struct {
Errors []registryError `json:"errors"`
}
func writeError(w http.ResponseWriter, status int, code, message string) {
err := registryErrors{
Errors: []registryError{
{code, message},
},
}
json, _ := json.Marshal(err)
w.WriteHeader(status)
w.Header().Add("Content-Type", "application/json")
w.Write(json)
}
type registryHandler struct {
ctx context.Context
state *builder.State
}
func (h *registryHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// Acknowledge that we speak V2 with an empty response
if r.RequestURI == "/v2/" {
return
}
// Serve the manifest (straight from Nix)
manifestMatches := manifestRegex.FindStringSubmatch(r.RequestURI)
if len(manifestMatches) == 3 {
imageName := manifestMatches[1]
imageTag := manifestMatches[2]
log.WithFields(log.Fields{
"image": imageName,
"tag": imageTag,
}).Info("requesting image manifest")
image := builder.ImageFromName(imageName, imageTag)
buildResult, err := builder.BuildImage(h.ctx, h.state, &image)
if err != nil {
writeError(w, 500, "UNKNOWN", "image build failure")
log.WithError(err).WithFields(log.Fields{
"image": imageName,
"tag": imageTag,
}).Error("failed to build image manifest")
return
}
// Some error types have special handling, which is applied
// here.
if buildResult.Error == "not_found" {
s := fmt.Sprintf("Could not find Nix packages: %v", buildResult.Pkgs)
writeError(w, 404, "MANIFEST_UNKNOWN", s)
log.WithFields(log.Fields{
"image": imageName,
"tag": imageTag,
"packages": buildResult.Pkgs,
}).Warn("could not find Nix packages")
return
}
// This marshaling error is ignored because we know that this
// field represents valid JSON data.
manifest, _ := json.Marshal(buildResult.Manifest)
w.Header().Add("Content-Type", manifestMediaType)
w.Write(manifest)
return
}
// Serve an image layer. For this we need to first ask Nix for
// the manifest, then proceed to extract the correct layer from
// it.
layerMatches := layerRegex.FindStringSubmatch(r.RequestURI)
if len(layerMatches) == 3 {
digest := layerMatches[2]
storage := h.state.Storage
err := storage.ServeLayer(digest, r, w)
if err != nil {
log.WithError(err).WithFields(log.Fields{
"layer": digest,
"backend": storage.Name(),
}).Error("failed to serve layer from storage backend")
}
return
}
log.WithField("uri", r.RequestURI).Info("unsupported registry route")
w.WriteHeader(404)
}
func main() {
cfg, err := config.FromEnv()
if err != nil {
log.WithError(err).Fatal("failed to load configuration")
}
var s storage.Backend
switch cfg.Backend {
case config.GCS:
s, err = storage.NewGCSBackend()
case config.FileSystem:
s, err = storage.NewFSBackend()
}
if err != nil {
log.WithError(err).Fatal("failed to initialise storage backend")
}
log.WithField("backend", s.Name()).Info("initialised storage backend")
ctx := context.Background()
cache, err := builder.NewCache()
if err != nil {
log.WithError(err).Fatal("failed to instantiate build cache")
}
var pop layers.Popularity
if cfg.PopUrl != "" {
pop, err = downloadPopularity(cfg.PopUrl)
if err != nil {
log.WithError(err).WithField("popURL", cfg.PopUrl).
Fatal("failed to fetch popularity information")
}
}
state := builder.State{
Cache: &cache,
Cfg: cfg,
Pop: pop,
Storage: s,
}
log.WithFields(log.Fields{
"version": version,
"port": cfg.Port,
}).Info("starting Nixery")
// All /v2/ requests belong to the registry handler.
http.Handle("/v2/", ®istryHandler{
ctx: ctx,
state: &state,
})
// All other roots are served by the static file server.
webDir := http.Dir(cfg.WebDir)
http.Handle("/", http.FileServer(webDir))
log.Fatal(http.ListenAndServe(":"+cfg.Port, nil))
}
