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#CDN over MongoDb GridFs

This utility can be used as stand alone Content Delivery Network, using MongoDB GridFs as backend file storage. It can be built from source code or installed as already compiled binaries.

Also it can be used as a thin file storage library for your projects, based on martini framework. For example, when you use one of the cloud platforms like Heroku, with ephemeral file system for application's instances and you have to save user's data.

• on the fly crop and resize for image/png and image/jpeg mimetypes
• cache strategy, based on HTTP Last-Modified header
• additional metadata for each file & aggregated statistic for it
• forced HTTP Content-Disposition header with the file name, for download links(only if flag is specified, see below)
• buckets(MongoDB collections) as separation level
• file listings for buckets, queried by metadata or without

Let's assume that the process is already running and listening to default http://localhost:5000.

$ curl -F field=@./books.jpg http://localhost:5000/example
{
  "error": null,
  "field":"/example/5364d634952b829316000001/books.jpg"
}

Uploading with metadata is realy simple - you only should specify it as GET parameters for uploading URL:

$ curl -F field=@./books.jpg "http://localhost:5000/example?userId=1&some_another_data=useful"
...

As expected, the URL for getting is:

http://localhost:5000/example/5364d634952b829316000001/books.jpg 

or

http://localhost:5000/example/5364d634952b829316000001

That means that the filename is not necessary.
For forsed downloading specify dl GET parameter:

http://localhost:5000/example/5364d634952b829316000001/books.jpg?dl

In this case the file will not be previewed in the browser.

This works only for files with mimetypes image/png & image/jpeg! In another cases it feature will be ignored.

Specify GET parameters crop, scrop or resize for URL. Crop example:

http://localhost:5000/example/5364d634952b829316000001/books.jpg?crop=500

The value should contain one or two(separated by one non-digit character) integer as width and height in pixels. If height is not specified, it will be used width value. For example, value crop=500 will be interpreted as crop=500x500.

scrop, resize parameter works the same way.
scrop - is smart crop, based on smartcrop library.

WARNING! Smartcrop algorithm may take a long time.

To get storage usage information in bytes, based on saved metadata, GET it like this:

$ http://localhost:5000/example/_stats?userId=1
{
  "fileSize": 204789
}

If metadata is not specified, usage information will be received for the whole bucket.

To get the listing of files, based on saved metadata, GET it like this:

$ http://localhost:5000/example?userId=1
[
  "/5364d634952b829316000001/books.jpg"
]

If metadata is not specified, usage information will be received for the whole bucket.

As library for martini framework.

$ go get github.com/olebedev/cdn

Simple server.go file:

package main

import (
	"log"
	"net/http"
	"os"
	"github.com/go-martini/martini"
	"github.com/olebedev/cdn/lib"
	"labix.org/v2/mgo"
)

// Acceess handler
func Access(res http.ResponseWriter, req *http.Request) {
	// check session or something like this
}

// Set prefix for current collection name, of course, if need it
// It useful when you store another data in one database
func AutoPrefix(params martini.Params) {
	// 'coll' - parameter name, which is used
	params["coll"] = "cdn." + params["coll"]
	// Ok. Now, cdn will work with this prefix for all collections
}

func main() {
	m := martini.Classic()

	session, err := mgo.Dial("localhost")
	if err != nil {
		panic(err)
	}
	session.SetMode(mgo.Monotonic, true)
	db := session.DB("cdn")
	m.Map(db)

	logger := log.New(os.Stdout, "\x1B[36m[cdn] >>\x1B[39m ", 0)
	m.Map(logger)

	m.Group("/uploads", 
		cdn.Cdn(cdn.Config{
			// Maximum width or height with pixels to crop or resize
			// Useful to high performance
			MaxSize:  1000,
			// Show statictics and the listing of files
			ShowInfo: true,
			// If true it send URL without collection name, like this:
			// {"field":"/5364d634952b829316000001/books.jpg", "error": null}
			TailOnly: true,
		}),
		// Access logic here
		Access,
		// On the fly prefix for collection
		AutoPrefix,
	)

	logger.Println("Server started at :3000")
	m.Run()
}

Let's start it!

$ go run server.go
[cdn] >> Server started at :3000

That's all. Now you have started CDN at http://localhost:3000/uploads/.

If you want to build it from sources:

$ go get github.com/olebedev/cdn

If you don't know what is Golang, check releases page and download binaries for your platform. Untar it and type this:

$ ./cdn --help
Usage of ./cdn:
  -maxSize="1000": 
  -mongo.name="cdn": 
  -mongo.uri="localhost": 
  -port="5000": 
  -showInfo="true": 
  -tailOnly="false":

• handler for 206 HTTP Status for large file
• cache(save to GridFs croppped & resized image files)