weasel

package module

v0.1.1 Latest Latest Go to latest Published: Jan 28, 2020 License: Apache-2.0 Imports: 19 Imported by: 0

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Repository

github.com/google/weasel

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README ¶

yummy-weasel

A simple frontend (App Engine app) that serves content from a Google Cloud Storage (GCS) bucket, while allowing for:

HTTPS on custom domain
support for Service Worker (works only over HTTPS)
HTTP/2 push
more robust redirect from naked custom domain
serving directly from naked custom domain
keep the deployment/publishing flow using just the existing GCS bucket, which has proven to be fast and reliable, with partial content updates.
dynamic server-side logic

design

The design is simple. Suppose you have a static website www.example.com, served directly from a GCS gs://www.example.com.

A very simplified picture of the serving path can be shown as follows.

+-----+    GET http://www.example.com/dir/index.html
| GCS |  <-----------------------------------------+  visitor
+-----+                                                 :-/

Weasel enhancement consists of modifying the serving path to:

+-----+   (2) GET gs://www.example.com/dir/index.html
| GCS |  <------------------------------+--------+
+-----+                                 | yummy  |
                                        | weasel |
                                        +--------+
                                           ↑  |
                                      (1)  |  | (3)
         GET https://www.example.com/dir/  |  ↓ Link: <asset>; rel=preload

                                         visitor
                                           :-)

A visitor requests the website page. Note that /index.html is now optional. Due to GCS restrictions, such suffixes were previously required for sub-folders, but with this approach they no longer need to be specified. Also, requests can (and will) be made over HTTPS.
Weasel fetches the object content from the original GCS bucket and caches it locally. This step is necessary only if the object hasn't been cached already or the cache has expired. Cache expiration and invalidation is based on GCS object cache-control header settings.
Weasel responds with the GCS object contents. Note that we can optionally push additional assets related to the requested file by using Link: <asset>; rel=preload header supported by GFE.

license

Apache License 2.0.

This is not an official Google product.

Documentation ¶

Overview ¶

Package weasel provides means for serving content from a Google Cloud Storage (GCS) bucket, suitable for hosting on Google App Engine. See README.md for the design details.

This package is a work in progress and makes no API stability promises.

Index ¶

Variables
func ValidMethod(m string) bool
type CORS
type FetchError
- func (e *FetchError) Error() string
type Object
- func (o *Object) Redirect() string
- func (o *Object) RedirectCode() int
type Storage

Constants ¶

This section is empty.

Variables ¶

View Source

var DefaultStorage = &Storage{
	Base:  "https://storage.googleapis.com",
	Index: "index.html",
	CORS: CORS{
		Origin: []string{"*"},
		MaxAge: "86400",
	},
}

DefaultStorage is a Storage with sensible default parameters.

Functions ¶

func ValidMethod ¶

func ValidMethod(m string) bool

ValidMethod reports whether m is a supported HTTP method.

Types ¶

type CORS ¶

type CORS struct {
	Origin []string // allowed origins
	MaxAge string   // preflight cache, in seconds
}

CORS is a Storage cross-origin settings.

type FetchError ¶

type FetchError struct {
	Msg  string
	Code int
}

FetchError contains error code and message from a GCS response.

func (*FetchError) Error ¶

func (e *FetchError) Error() string

Error returns formatted FetchError.

type Object ¶

type Object struct {
	Meta map[string]string
	Body io.ReadCloser
}

Object represents a single GCS object.

func (*Object) Redirect ¶

func (o *Object) Redirect() string

Redirect returns o's redirect URL, zero string otherwise.

func (*Object) RedirectCode ¶

func (o *Object) RedirectCode() int

RedirectCode returns o's HTTP response code for redirect. It defaults to http.StatusMovedPermanently.

type Storage ¶

type Storage struct {
	Base  string // GCS service base URL, e.g. "https://storage.googleapis.com".
	Index string // Appended to an object name in certain cases, e.g. "index.html".
	CORS  CORS
}

Storage incapsulates configuration params for retrieveing and serving GCS objects.

func (*Storage) CacheKey ¶

func (s *Storage) CacheKey(bucket, name string) string

CacheKey returns a key to cache an object under, computed from s.Base, bucket and then name.

func (*Storage) HandleChangeHook ¶

func (s *Storage) HandleChangeHook(w http.ResponseWriter, r *http.Request)

HandleChangeHook handles Object Change Notifications as described at https://cloud.google.com/storage/docs/object-change-notification. It removes objects from cache.

func (*Storage) Open ¶

func (s *Storage) Open(ctx context.Context, bucket, name string) (*Object, error)

Open retrieves GCS object name of the bucket from cache or network. Objects fetched from the network are cached before returning from this function.

func (*Storage) OpenFile ¶

func (s *Storage) OpenFile(ctx context.Context, bucket, name string) (*Object, error)

OpenFile abstracts Open and treats object name like a file path.

func (*Storage) PurgeCache ¶

func (s *Storage) PurgeCache(ctx context.Context, bucket, name string) error

PurgeCache removes cached object from memcache. It does not return an error in the case of cache miss.

func (*Storage) ServeObject ¶

func (s *Storage) ServeObject(w http.ResponseWriter, r *http.Request, o *Object) error

ServeObject writes object o to w, with optional body and CORS headers, based on the in-flight request r.

func (*Storage) Stat ¶

func (s *Storage) Stat(ctx context.Context, bucket, name string) (*Object, error)

Stat is similar to Read except the returned Object.Body may be nil. In the case where Body is not nil, calling Body.Close() is not required.

Source Files ¶

View all Source files

Directories ¶

Path	Synopsis
internal Package internal contains utilities internal to the weasel packages.	Package internal contains utilities internal to the weasel packages.
server Package server provides a simple frontend in form of an App Engine app built atop the weasel.Storage.	Package server provides a simple frontend in form of an App Engine app built atop the weasel.Storage.

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