refactor(server): Introduce pluggable interface for storage backends

This abstracts over the functionality of Google Cloud Storage and
other potential underlying storage backends to make it possible to
replace these in Nixery.

The GCS backend is not yet reimplemented.
This commit is contained in:
Vincent Ambo 2019-10-27 16:49:54 +01:00 committed by Vincent Ambo
parent 7c647a538a
commit bb54c4eb3d
5 changed files with 110 additions and 228 deletions

View File

@ -28,18 +28,16 @@ import (
"io"
"io/ioutil"
"net/http"
"net/url"
"os"
"os/exec"
"sort"
"strings"
"cloud.google.com/go/storage"
"github.com/google/nixery/server/config"
"github.com/google/nixery/server/layers"
"github.com/google/nixery/server/manifest"
"github.com/google/nixery/server/storage"
log "github.com/sirupsen/logrus"
"golang.org/x/oauth2/google"
)
// The maximum number of layers in an image is 125. To allow for
@ -47,19 +45,16 @@ import (
// use up is set at a lower point.
const LayerBudget int = 94
// API scope needed for renaming objects in GCS
const gcsScope = "https://www.googleapis.com/auth/devstorage.read_write"
// HTTP client to use for direct calls to APIs that are not part of the SDK
var client = &http.Client{}
// State holds the runtime state that is carried around in Nixery and
// passed to builder functions.
type State struct {
Bucket *storage.BucketHandle
Cache *LocalCache
Cfg config.Config
Pop layers.Popularity
Storage storage.Backend
Cache *LocalCache
Cfg config.Config
Pop layers.Popularity
}
// Image represents the information necessary for building a container image.
@ -349,53 +344,6 @@ func prepareLayers(ctx context.Context, s *State, image *Image, result *ImageRes
return entries, nil
}
// renameObject renames an object in the specified Cloud Storage
// bucket.
//
// The Go API for Cloud Storage does not support renaming objects, but
// the HTTP API does. The code below makes the relevant call manually.
func renameObject(ctx context.Context, s *State, old, new string) error {
bucket := s.Cfg.Bucket
creds, err := google.FindDefaultCredentials(ctx, gcsScope)
if err != nil {
return err
}
token, err := creds.TokenSource.Token()
if err != nil {
return err
}
// as per https://cloud.google.com/storage/docs/renaming-copying-moving-objects#rename
url := fmt.Sprintf(
"https://www.googleapis.com/storage/v1/b/%s/o/%s/rewriteTo/b/%s/o/%s",
url.PathEscape(bucket), url.PathEscape(old),
url.PathEscape(bucket), url.PathEscape(new),
)
req, err := http.NewRequest("POST", url, nil)
req.Header.Add("Authorization", "Bearer "+token.AccessToken)
_, err = client.Do(req)
if err != nil {
return err
}
// It seems that 'rewriteTo' copies objects instead of
// renaming/moving them, hence a deletion call afterwards is
// required.
if err = s.Bucket.Object(old).Delete(ctx); err != nil {
log.WithError(err).WithFields(log.Fields{
"new": new,
"old": old,
}).Warn("failed to delete renamed object")
// this error should not break renaming and is not returned
}
return nil
}
// layerWriter is the type for functions that can write a layer to the
// multiwriter used for uploading & hashing.
//
@ -430,33 +378,32 @@ func (b *byteCounter) Write(p []byte) (n int, err error) {
// The return value is the layer's SHA256 hash, which is used in the
// image manifest.
func uploadHashLayer(ctx context.Context, s *State, key string, lw layerWriter) (*manifest.Entry, error) {
staging := s.Bucket.Object("staging/" + key)
path := "staging/" + key
sha256sum, size, err := s.Storage.Persist(path, func(sw io.Writer) (string, int64, error) {
// Sets up a "multiwriter" that simultaneously runs both hash
// algorithms and uploads to the storage backend.
shasum := sha256.New()
counter := &byteCounter{}
multi := io.MultiWriter(sw, shasum, counter)
// Sets up a "multiwriter" that simultaneously runs both hash
// algorithms and uploads to the bucket
sw := staging.NewWriter(ctx)
shasum := sha256.New()
counter := &byteCounter{}
multi := io.MultiWriter(sw, shasum, counter)
err := lw(multi)
sha256sum := fmt.Sprintf("%x", shasum.Sum([]byte{}))
return sha256sum, counter.count, err
})
err := lw(multi)
if err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to create and upload layer")
log.WithError(err).WithFields(log.Fields{
"layer": key,
"backend": s.Storage.Name(),
}).Error("failed to create and store layer")
return nil, err
}
if err = sw.Close(); err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to upload layer to staging")
}
sha256sum := fmt.Sprintf("%x", shasum.Sum([]byte{}))
// Hashes are now known and the object is in the bucket, what
// remains is to move it to the correct location and cache it.
err = renameObject(ctx, s, "staging/"+key, "layers/"+sha256sum)
err = s.Storage.Move("staging/"+key, "layers/"+sha256sum)
if err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to move layer from staging")
@ -464,8 +411,6 @@ func uploadHashLayer(ctx context.Context, s *State, key string, lw layerWriter)
return nil, err
}
size := counter.count
log.WithFields(log.Fields{
"layer": key,
"sha256": sha256sum,

View File

@ -114,24 +114,18 @@ func (c *LocalCache) localCacheLayer(key string, e manifest.Entry) {
}
// Retrieve a manifest from the cache(s). First the local cache is
// checked, then the GCS-bucket cache.
// checked, then the storage backend.
func manifestFromCache(ctx context.Context, s *State, key string) (json.RawMessage, bool) {
if m, cached := s.Cache.manifestFromLocalCache(key); cached {
return m, true
}
obj := s.Bucket.Object("manifests/" + key)
// Probe whether the file exists before trying to fetch it.
_, err := obj.Attrs(ctx)
r, err := s.Storage.Fetch("manifests/" + key)
if err != nil {
return nil, false
}
r, err := obj.NewReader(ctx)
if err != nil {
log.WithError(err).WithField("manifest", key).
Error("failed to retrieve manifest from bucket cache")
log.WithError(err).WithFields(log.Fields{
"manifest": key,
"backend": s.Storage.Name(),
})
return nil, false
}
@ -139,8 +133,10 @@ func manifestFromCache(ctx context.Context, s *State, key string) (json.RawMessa
m, err := ioutil.ReadAll(r)
if err != nil {
log.WithError(err).WithField("manifest", key).
Error("failed to read cached manifest from bucket")
log.WithError(err).WithFields(log.Fields{
"manifest": key,
"backend": s.Storage.Name(),
}).Error("failed to read cached manifest from storage backend")
return nil, false
}
@ -155,21 +151,17 @@ func manifestFromCache(ctx context.Context, s *State, key string) (json.RawMessa
func cacheManifest(ctx context.Context, s *State, key string, m json.RawMessage) {
go s.Cache.localCacheManifest(key, m)
obj := s.Bucket.Object("manifests/" + key)
w := obj.NewWriter(ctx)
r := bytes.NewReader([]byte(m))
path := "manifests/" + key
_, size, err := s.Storage.Persist(path, func(w io.Writer) (string, int64, error) {
size, err := io.Copy(w, bytes.NewReader([]byte(m)))
return "", size, err
})
size, err := io.Copy(w, r)
if err != nil {
log.WithError(err).WithField("manifest", key).
Error("failed to cache manifest to GCS")
return
}
if err = w.Close(); err != nil {
log.WithError(err).WithField("manifest", key).
Error("failed to cache manifest to GCS")
log.WithError(err).WithFields(log.Fields{
"manifest": key,
"backend": s.Storage.Name(),
}).Error("failed to cache manifest to storage backend")
return
}
@ -177,7 +169,8 @@ func cacheManifest(ctx context.Context, s *State, key string, m json.RawMessage)
log.WithFields(log.Fields{
"manifest": key,
"size": size,
}).Info("cached manifest to GCS")
"backend": s.Storage.Name(),
}).Info("cached manifest to storage backend")
}
// Retrieve a layer build from the cache, first checking the local
@ -187,16 +180,12 @@ func layerFromCache(ctx context.Context, s *State, key string) (*manifest.Entry,
return entry, true
}
obj := s.Bucket.Object("builds/" + key)
_, err := obj.Attrs(ctx)
r, err := s.Storage.Fetch("builds/" + key)
if err != nil {
return nil, false
}
r, err := obj.NewReader(ctx)
if err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to retrieve cached layer from GCS")
log.WithError(err).WithFields(log.Fields{
"layer": key,
"backend": s.Storage.Name(),
}).Warn("failed to retrieve cached layer from storage backend")
return nil, false
}
@ -205,8 +194,10 @@ func layerFromCache(ctx context.Context, s *State, key string) (*manifest.Entry,
jb := bytes.NewBuffer([]byte{})
_, err = io.Copy(jb, r)
if err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to read cached layer from GCS")
log.WithError(err).WithFields(log.Fields{
"layer": key,
"backend": s.Storage.Name(),
}).Error("failed to read cached layer from storage backend")
return nil, false
}
@ -227,24 +218,19 @@ func layerFromCache(ctx context.Context, s *State, key string) (*manifest.Entry,
func cacheLayer(ctx context.Context, s *State, key string, entry manifest.Entry) {
s.Cache.localCacheLayer(key, entry)
obj := s.Bucket.Object("builds/" + key)
j, _ := json.Marshal(&entry)
path := "builds/" + key
_, _, err := s.Storage.Persist(path, func(w io.Writer) (string, int64, error) {
size, err := io.Copy(w, bytes.NewReader(j))
return "", size, err
})
w := obj.NewWriter(ctx)
_, err := io.Copy(w, bytes.NewReader(j))
if err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to cache layer")
return
log.WithError(err).WithFields(log.Fields{
"layer": key,
"backend": s.Storage.Name(),
}).Error("failed to cache layer")
}
if err = w.Close(); err != nil {
log.WithError(err).WithField("layer", key).
Error("failed to cache layer")
return
}
return
}

View File

@ -18,42 +18,11 @@
package config
import (
"io/ioutil"
"os"
"cloud.google.com/go/storage"
log "github.com/sirupsen/logrus"
"golang.org/x/oauth2/google"
)
// Configure GCS URL signing in the presence of a service account key
// (toggled if the user has set GOOGLE_APPLICATION_CREDENTIALS).
func signingOptsFromEnv() *storage.SignedURLOptions {
path := os.Getenv("GOOGLE_APPLICATION_CREDENTIALS")
if path == "" {
return nil
}
key, err := ioutil.ReadFile(path)
if err != nil {
log.WithError(err).WithField("file", path).Fatal("failed to read service account key")
}
conf, err := google.JWTConfigFromJSON(key)
if err != nil {
log.WithError(err).WithField("file", path).Fatal("failed to parse service account key")
}
log.WithField("account", conf.Email).Info("GCS URL signing enabled")
return &storage.SignedURLOptions{
Scheme: storage.SigningSchemeV4,
GoogleAccessID: conf.Email,
PrivateKey: conf.PrivateKey,
Method: "GET",
}
}
func getConfig(key, desc, def string) string {
value := os.Getenv(key)
if value == "" && def == "" {
@ -70,13 +39,11 @@ func getConfig(key, desc, def string) string {
// Config holds the Nixery configuration options.
type Config struct {
Bucket string // GCS bucket to cache & serve layers
Signing *storage.SignedURLOptions // Signing options to use for GCS URLs
Port string // Port on which to launch HTTP server
Pkgs PkgSource // Source for Nix package set
Timeout string // Timeout for a single Nix builder (seconds)
WebDir string // Directory with static web assets
PopUrl string // URL to the Nix package popularity count
Port string // Port on which to launch HTTP server
Pkgs PkgSource // Source for Nix package set
Timeout string // Timeout for a single Nix builder (seconds)
WebDir string // Directory with static web assets
PopUrl string // URL to the Nix package popularity count
}
func FromEnv() (Config, error) {
@ -86,10 +53,8 @@ func FromEnv() (Config, error) {
}
return Config{
Bucket: getConfig("BUCKET", "GCS bucket for layer storage", ""),
Port: getConfig("PORT", "HTTP port", ""),
Pkgs: pkgs,
Signing: signingOptsFromEnv(),
Timeout: getConfig("NIX_TIMEOUT", "Nix builder timeout", "60"),
WebDir: getConfig("WEB_DIR", "Static web file dir", ""),
PopUrl: os.Getenv("NIX_POPULARITY_URL"),

View File

@ -32,9 +32,7 @@ import (
"io/ioutil"
"net/http"
"regexp"
"time"
"cloud.google.com/go/storage"
"github.com/google/nixery/server/builder"
"github.com/google/nixery/server/config"
"github.com/google/nixery/server/layers"
@ -59,49 +57,6 @@ var (
layerRegex = regexp.MustCompile(`^/v2/([\w|\-|\.|\_|\/]+)/blobs/sha256:(\w+)$`)
)
// layerRedirect constructs the public URL of the layer object in the Cloud
// Storage bucket, signs it and redirects the user there.
//
// Signing the URL allows unauthenticated clients to retrieve objects from the
// bucket.
//
// The Docker client is known to follow redirects, but this might not be true
// for all other registry clients.
func constructLayerUrl(cfg *config.Config, digest string) (string, error) {
log.WithField("layer", digest).Info("redirecting layer request to bucket")
object := "layers/" + digest
if cfg.Signing != nil {
opts := *cfg.Signing
opts.Expires = time.Now().Add(5 * time.Minute)
return storage.SignedURL(cfg.Bucket, object, &opts)
} else {
return ("https://storage.googleapis.com/" + cfg.Bucket + "/" + object), nil
}
}
// prepareBucket configures the handle to a Cloud Storage bucket in which
// individual layers will be stored after Nix builds. Nixery does not directly
// serve layers to registry clients, instead it redirects them to the public
// URLs of the Cloud Storage bucket.
//
// The bucket is required for Nixery to function correctly, hence fatal errors
// are generated in case it fails to be set up correctly.
func prepareBucket(ctx context.Context, cfg *config.Config) *storage.BucketHandle {
client, err := storage.NewClient(ctx)
if err != nil {
log.WithError(err).Fatal("failed to set up Cloud Storage client")
}
bkt := client.Bucket(cfg.Bucket)
if _, err := bkt.Attrs(ctx); err != nil {
log.WithError(err).WithField("bucket", cfg.Bucket).Fatal("could not access configured bucket")
}
return bkt
}
// Downloads the popularity information for the package set from the
// URL specified in Nixery's configuration.
func downloadPopularity(url string) (layers.Popularity, error) {
@ -218,16 +173,15 @@ func (h *registryHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
layerMatches := layerRegex.FindStringSubmatch(r.RequestURI)
if len(layerMatches) == 3 {
digest := layerMatches[2]
url, err := constructLayerUrl(&h.state.Cfg, digest)
storage := h.state.Storage
err := storage.ServeLayer(digest, w)
if err != nil {
log.WithError(err).WithField("layer", digest).Error("failed to sign GCS URL")
writeError(w, 500, "UNKNOWN", "could not serve layer")
return
log.WithError(err).WithFields(log.Fields{
"layer": digest,
"backend": storage.Name(),
}).Error("failed to serve layer from storage backend")
}
w.Header().Set("Location", url)
w.WriteHeader(303)
return
}
@ -243,7 +197,6 @@ func main() {
}
ctx := context.Background()
bucket := prepareBucket(ctx, &cfg)
cache, err := builder.NewCache()
if err != nil {
log.WithError(err).Fatal("failed to instantiate build cache")
@ -259,10 +212,9 @@ func main() {
}
state := builder.State{
Bucket: bucket,
Cache: &cache,
Cfg: cfg,
Pop: pop,
Cache: &cache,
Cfg: cfg,
Pop: pop,
}
log.WithFields(log.Fields{

34
server/storage/storage.go Normal file
View File

@ -0,0 +1,34 @@
// Package storage implements an interface that can be implemented by
// storage backends, such as Google Cloud Storage or the local
// filesystem.
package storage
import (
"io"
"net/http"
)
type Backend interface {
// Name returns the name of the storage backend, for use in
// log messages and such.
Name() string
// Persist provides a user-supplied function with a writer
// that stores data in the storage backend.
//
// It needs to return the SHA256 hash of the data written as
// well as the total number of bytes, as those are required
// for the image manifest.
Persist(string, func(io.Writer) (string, int64, error)) (string, int64, error)
// Fetch retrieves data from the storage backend.
Fetch(path string) (io.ReadCloser, error)
// Move renames a path inside the storage backend. This is
// used for staging uploads while calculating their hashes.
Move(old, new string) error
// Serve provides a handler function to serve HTTP requests
// for layers in the storage backend.
ServeLayer(digest string, w http.ResponseWriter) error
}