fix(server): Thread request context to all relevant places

Previously background contexts where created where necessary (e.g. in
GCS interactions). Should I begin to use request timeouts or other
context-dependent things in the future, it's useful to have the actual
HTTP request context around.

This threads the request context through the application to all places
that need it.

6 files changed, 20 insertions, 23 deletions

diff --git a/tools/nixery/server/builder/builder.go b/tools/nixery/server/builder/builder.go
index 021cc662c56d..59158037e443 100644
--- a/tools/nixery/server/builder/builder.go
+++ b/tools/nixery/server/builder/builder.go
@@ -375,7 +375,7 @@ func (b *byteCounter) Write(p []byte) (n int, err error) {
 // image manifest.
 func uploadHashLayer(ctx context.Context, s *State, key string, lw layerWriter) (*manifest.Entry, error) {
 	path := "staging/" + key
-	sha256sum, size, err := s.Storage.Persist(path, func(sw io.Writer) (string, int64, error) {
+	sha256sum, size, err := s.Storage.Persist(ctx, 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()
@@ -399,7 +399,7 @@ func uploadHashLayer(ctx context.Context, s *State, key string, lw layerWriter)
 
 	// 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 = s.Storage.Move("staging/"+key, "layers/"+sha256sum)
+	err = s.Storage.Move(ctx, "staging/"+key, "layers/"+sha256sum)
 	if err != nil {
 		log.WithError(err).WithField("layer", key).
 			Error("failed to move layer from staging")
diff --git a/tools/nixery/server/builder/cache.go b/tools/nixery/server/builder/cache.go
index 07ac9746d5f0..82bd90927cd0 100644
--- a/tools/nixery/server/builder/cache.go
+++ b/tools/nixery/server/builder/cache.go
@@ -120,7 +120,7 @@ func manifestFromCache(ctx context.Context, s *State, key string) (json.RawMessa
 		return m, true
 	}
 
-	r, err := s.Storage.Fetch("manifests/" + key)
+	r, err := s.Storage.Fetch(ctx, "manifests/"+key)
 	if err != nil {
 		log.WithError(err).WithFields(log.Fields{
 			"manifest": key,
@@ -152,7 +152,7 @@ func cacheManifest(ctx context.Context, s *State, key string, m json.RawMessage)
 	go s.Cache.localCacheManifest(key, m)
 
 	path := "manifests/" + key
-	_, size, err := s.Storage.Persist(path, func(w io.Writer) (string, int64, error) {
+	_, size, err := s.Storage.Persist(ctx, path, func(w io.Writer) (string, int64, error) {
 		size, err := io.Copy(w, bytes.NewReader([]byte(m)))
 		return "", size, err
 	})
@@ -180,7 +180,7 @@ func layerFromCache(ctx context.Context, s *State, key string) (*manifest.Entry,
 		return entry, true
 	}
 
-	r, err := s.Storage.Fetch("builds/" + key)
+	r, err := s.Storage.Fetch(ctx, "builds/"+key)
 	if err != nil {
 		log.WithError(err).WithFields(log.Fields{
 			"layer":   key,
@@ -220,7 +220,7 @@ func cacheLayer(ctx context.Context, s *State, key string, entry manifest.Entry)
 
 	j, _ := json.Marshal(&entry)
 	path := "builds/" + key
-	_, _, err := s.Storage.Persist(path, func(w io.Writer) (string, int64, error) {
+	_, _, err := s.Storage.Persist(ctx, path, func(w io.Writer) (string, int64, error) {
 		size, err := io.Copy(w, bytes.NewReader(j))
 		return "", size, err
 	})
diff --git a/tools/nixery/server/main.go b/tools/nixery/server/main.go
index f4f707313f22..6ae0730906dc 100644
--- a/tools/nixery/server/main.go
+++ b/tools/nixery/server/main.go
@@ -26,7 +26,6 @@
 package main
 
 import (
-	"context"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
@@ -110,7 +109,6 @@ func writeError(w http.ResponseWriter, status int, code, message string) {
 }
 
 type registryHandler struct {
-	ctx   context.Context
 	state *builder.State
 }
 
@@ -132,7 +130,7 @@ func (h *registryHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		}).Info("requesting image manifest")
 
 		image := builder.ImageFromName(imageName, imageTag)
-		buildResult, err := builder.BuildImage(h.ctx, h.state, &image)
+		buildResult, err := builder.BuildImage(r.Context(), h.state, &image)
 
 		if err != nil {
 			writeError(w, 500, "UNKNOWN", "image build failure")
@@ -211,7 +209,6 @@ func main() {
 
 	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")
@@ -240,7 +237,6 @@ func main() {
 
 	// All /v2/ requests belong to the registry handler.
 	http.Handle("/v2/", &registryHandler{
-		ctx:   ctx,
 		state: &state,
 	})
 
diff --git a/tools/nixery/server/storage/filesystem.go b/tools/nixery/server/storage/filesystem.go
index 8aca20aac2d0..3fb91bc5e134 100644
--- a/tools/nixery/server/storage/filesystem.go
+++ b/tools/nixery/server/storage/filesystem.go
@@ -2,6 +2,7 @@
 package storage
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"net/http"
@@ -34,7 +35,7 @@ func (b *FSBackend) Name() string {
 	return fmt.Sprintf("Filesystem (%s)", b.path)
 }
 
-func (b *FSBackend) Persist(key string, f func(io.Writer) (string, int64, error)) (string, int64, error) {
+func (b *FSBackend) Persist(ctx context.Context, key string, f Persister) (string, int64, error) {
 	full := path.Join(b.path, key)
 	dir := path.Dir(full)
 	err := os.MkdirAll(dir, 0755)
@@ -53,12 +54,12 @@ func (b *FSBackend) Persist(key string, f func(io.Writer) (string, int64, error)
 	return f(file)
 }
 
-func (b *FSBackend) Fetch(key string) (io.ReadCloser, error) {
+func (b *FSBackend) Fetch(ctx context.Context, key string) (io.ReadCloser, error) {
 	full := path.Join(b.path, key)
 	return os.Open(full)
 }
 
-func (b *FSBackend) Move(old, new string) error {
+func (b *FSBackend) Move(ctx context.Context, old, new string) error {
 	newpath := path.Join(b.path, new)
 	err := os.MkdirAll(path.Dir(newpath), 0755)
 	if err != nil {
diff --git a/tools/nixery/server/storage/gcs.go b/tools/nixery/server/storage/gcs.go
index 749c7ba150e5..b9d70ef20488 100644
--- a/tools/nixery/server/storage/gcs.go
+++ b/tools/nixery/server/storage/gcs.go
@@ -66,8 +66,7 @@ func (b *GCSBackend) Name() string {
 	return "Google Cloud Storage (" + b.bucket + ")"
 }
 
-func (b *GCSBackend) Persist(path string, f func(io.Writer) (string, int64, error)) (string, int64, error) {
-	ctx := context.Background()
+func (b *GCSBackend) Persist(ctx context.Context, path string, f Persister) (string, int64, error) {
 	obj := b.handle.Object(path)
 	w := obj.NewWriter(ctx)
 
@@ -80,8 +79,7 @@ func (b *GCSBackend) Persist(path string, f func(io.Writer) (string, int64, erro
 	return hash, size, w.Close()
 }
 
-func (b *GCSBackend) Fetch(path string) (io.ReadCloser, error) {
-	ctx := context.Background()
+func (b *GCSBackend) Fetch(ctx context.Context, path string) (io.ReadCloser, error) {
 	obj := b.handle.Object(path)
 
 	// Probe whether the file exists before trying to fetch it
@@ -98,8 +96,7 @@ func (b *GCSBackend) Fetch(path string) (io.ReadCloser, error) {
 //
 // 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 (b *GCSBackend) Move(old, new string) error {
-	ctx := context.Background()
+func (b *GCSBackend) Move(ctx context.Context, old, new string) error {
 	creds, err := google.FindDefaultCredentials(ctx, gcsScope)
 	if err != nil {
 		return err
diff --git a/tools/nixery/server/storage/storage.go b/tools/nixery/server/storage/storage.go
index ad10d682e93a..70095cba4334 100644
--- a/tools/nixery/server/storage/storage.go
+++ b/tools/nixery/server/storage/storage.go
@@ -4,10 +4,13 @@
 package storage
 
 import (
+	"context"
 	"io"
 	"net/http"
 )
 
+type Persister = func(io.Writer) (string, int64, error)
+
 type Backend interface {
 	// Name returns the name of the storage backend, for use in
 	// log messages and such.
@@ -19,14 +22,14 @@ type Backend interface {
 	// 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)
+	Persist(context.Context, string, Persister) (string, int64, error)
 
 	// Fetch retrieves data from the storage backend.
-	Fetch(path string) (io.ReadCloser, error)
+	Fetch(ctx context.Context, 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
+	Move(ctx context.Context, old, new string) error
 
 	// Serve provides a handler function to serve HTTP requests
 	// for layers in the storage backend.