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style(main): Reflow comments to 80 characters maximum

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This commit is contained in:
Vincent Ambo 2019-07-23 22:56:18 +01:00
parent db1086a5bb
commit 8314568199
1 changed files with 51 additions and 42 deletions
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93
tools/nixery/main.go
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@ -40,31 +40,31 @@ type config struct {
port string // Port on which to launch HTTP server
}
// ManifestMediaType is the Content-Type used for the manifest itself.
// This corresponds to the "Image Manifest V2, Schema 2" described on
// this page:
// 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"
// Image represents the information necessary for building a container image. This can
// be either a list of package names (corresponding to keys in the nixpkgs set) or a
// Nix expression that results in a *list* of derivations.
// Image represents the information necessary for building a container image.
// This can be either a list of package names (corresponding to keys in the
// nixpkgs set) or a Nix expression that results in a *list* of derivations.
type image struct {
// Name of the container image.
name string
// Names of packages to include in the image. These must correspond directly to
// top-level names of Nix packages in the nixpkgs tree.
// Names of packages to include in the image. These must correspond
// directly to top-level names of Nix packages in the nixpkgs tree.
packages []string
}
// BuildResult represents the output of calling the Nix derivation responsible for building
// registry images.
// BuildResult represents the output of calling the Nix derivation responsible
// for building registry images.
//
// The `layerLocations` field contains the local filesystem paths to each individual image layer
// that will need to be served, while the `manifest` field contains the JSON-representation of
// the manifest that needs to be served to the client.
// The `layerLocations` field contains the local filesystem paths to each
// individual image layer that will need to be served, while the `manifest`
// field contains the JSON-representation of the manifest that needs to be
// served to the client.
//
// The later field is simply treated as opaque JSON and passed through.
type BuildResult struct {
@ -78,7 +78,8 @@ type BuildResult struct {
// imageFromName parses an image name into the corresponding structure which can
// be used to invoke Nix.
//
// It will expand convenience names under the hood (see the `convenienceNames` function below).
// It will expand convenience names under the hood (see the `convenienceNames`
// function below).
func imageFromName(name string) image {
packages := strings.Split(name, "/")
return image{
@ -87,15 +88,15 @@ func imageFromName(name string) image {
}
}
// convenienceNames expands convenience package names defined by Nixery which let users
// include commonly required sets of tools in a container quickly.
// convenienceNames expands convenience package names defined by Nixery which
// let users include commonly required sets of tools in a container quickly.
//
// Convenience names must be specified as the first package in an image.
//
// Currently defined convenience names are:
//
// * `shell`: Includes bash, coreutils and other common command-line tools
// * `builder`: Includes the standard build environment, as well as everything from `shell`
// * `builder`: All of the above and the standard build environment
func convenienceNames(packages []string) []string {
shellPackages := []string{"bashInteractive", "coreutils", "moreutils", "nano"}
builderPackages := append(shellPackages, "stdenv")
@ -109,8 +110,8 @@ func convenienceNames(packages []string) []string {
}
}
// Call out to Nix and request that an image be built. Nix will, upon success, return
// a manifest for the container image.
// Call out to Nix and request that an image be built. Nix will, upon success,
// return a manifest for the container image.
func buildImage(ctx *context.Context, cfg *config, image *image, bucket *storage.BucketHandle) ([]byte, error) {
packages, err := json.Marshal(image.packages)
if err != nil {
@ -139,7 +140,7 @@ func buildImage(ctx *context.Context, cfg *config, image *image, bucket *storage
log.Println("Error starting nix-build:", err)
return nil, err
}
log.Printf("Started Nix image build for ''%s'", image.name)
log.Printf("Started Nix image build for '%s'", image.name)
stdout, _ := ioutil.ReadAll(outpipe)
stderr, _ := ioutil.ReadAll(errpipe)
@ -157,8 +158,9 @@ func buildImage(ctx *context.Context, cfg *config, image *image, bucket *storage
return nil, err
}
// The build output returned by Nix is deserialised to add all contained layers to the
// bucket. Only the manifest itself is re-serialised to JSON and returned.
// The build output returned by Nix is deserialised to add all
// contained layers to the bucket. Only the manifest itself is
// re-serialised to JSON and returned.
var result BuildResult
err = json.Unmarshal(buildOutput, &result)
if err != nil {
@ -175,19 +177,20 @@ func buildImage(ctx *context.Context, cfg *config, image *image, bucket *storage
return json.Marshal(result.Manifest)
}
// uploadLayer uploads a single layer to Cloud Storage bucket. Before writing any data
// the bucket is probed to see if the file already exists.
// uploadLayer uploads a single layer to Cloud Storage bucket. Before writing
// any data the bucket is probed to see if the file already exists.
//
// If the file does exist, its MD5 hash is verified to ensure that the stored file is
// not - for example - a fragment of a previous, incomplete upload.
// If the file does exist, its MD5 hash is verified to ensure that the stored
// file is not - for example - a fragment of a previous, incomplete upload.
func uploadLayer(ctx *context.Context, bucket *storage.BucketHandle, layer string, path string, md5 []byte) error {
layerKey := fmt.Sprintf("layers/%s", layer)
obj := bucket.Object(layerKey)
// Before uploading a layer to the bucket, probe whether it already exists.
// Before uploading a layer to the bucket, probe whether it already
// exists.
//
// If it does and the MD5 checksum matches the expected one, the layer upload
// can be skipped.
// If it does and the MD5 checksum matches the expected one, the layer
// upload can be skipped.
attrs, err := obj.Attrs(*ctx)
if err == nil && bytes.Equal(attrs.MD5, md5) {
@ -215,11 +218,11 @@ func uploadLayer(ctx *context.Context, bucket *storage.BucketHandle, layer strin
return nil
}
// layerRedirect constructs the public URL of the layer object in the Cloud Storage bucket
// and redirects the client there.
// layerRedirect constructs the public URL of the layer object in the Cloud
// Storage bucket and redirects the client there.
//
// The Docker client is known to follow redirects, but this might not
// be true for all other registry clients.
// The Docker client is known to follow redirects, but this might not be true
// for all other registry clients.
func layerRedirect(w http.ResponseWriter, cfg *config, digest string) {
log.Printf("Redirecting layer '%s' request to bucket '%s'\n", digest, cfg.bucket)
url := fmt.Sprintf("https://storage.googleapis.com/%s/layers/%s", cfg.bucket, digest)
@ -227,12 +230,13 @@ func layerRedirect(w http.ResponseWriter, cfg *config, digest string) {
w.WriteHeader(303)
}
// 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.
// 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.
// 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) *storage.BucketHandle {
client, err := storage.NewClient(*ctx)
if err != nil {
@ -274,13 +278,17 @@ func main() {
log.Printf("Starting Kubernetes Nix controller on port %s\n", cfg.port)
log.Fatal(http.ListenAndServe(":"+cfg.port, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
// When running on AppEngine, HTTP traffic should be redirected
// to HTTPS.
//
// This is achieved here by enforcing HSTS (with a one week duration) on responses.
// This is achieved here by enforcing HSTS (with a one week
// duration) on responses.
if r.Header.Get("X-Forwarded-Proto") == "http" && strings.Contains(r.Host, "appspot.com") {
w.Header().Add("Strict-Transport-Security", "max-age=604800")
}
// Serve an index page to anyone who visits the registry's base URL:
// Serve an index page to anyone who visits the registry's base
// URL:
if r.RequestURI == "/" {
index, _ := ioutil.ReadFile(cfg.web + "/index.html")
w.Header().Add("Content-Type", "text/html")
@ -312,8 +320,9 @@ func main() {
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.
// 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]