Coce

A cover image URLs cache exposing its content as a REST web service.

In various softwares (ILS for example), Book (or other kind of resources) cover image is displayed in front of the resource. Those images are fetched automatically from providers, such as Google or Amazon. Providers propose web services to retrieve information on Books from an ID (ISBN for example).

• Google API
• Amazon Product Advertising API
• Open Library Read API

With Coce, the cover images URL from various providers are cached in a Redis server. Client send REST request to Coce which reply with cached URL, or if not available in its cache retrieving them from providers. In its request, the client specify a providers order (for example aws,gb,ol for AWS, Google, and then Open Library): Coce send the first available URL.

Installation

• Install and start a Redis server

• Install node.js libraries:

    npm install express redis aws-lib util
  

• Configure Code operation by editing config.json

  • port - port on which the server respond
  • providers - array of available providers: gb,aws,ol
  • timeout - timeout in miliseconds for the service. Above this value, Coce stops waiting response from providers
  • redis - Redis server parameters:
    • host
    • port
    • timeout
  • gb - Google Books parameters:
    • timeout - timeout of the cached URL from Google Books
  • ol - Open Library parameters:
    • timeout - timeout of the cached URL from Open Library. Affter this delay, an URL is automatically removed from the cache, and so has to be re-fetched again if requested
    • imageSize - size of images: small, medium, large
  • aws - Amazon parameters:
    • accessKeyId
    • secretAccessKey
    • associateTag
    • imageSize - size of images: SmallImage, MediumImage, LargeImage

Start

cd _Coce HOME_
node webservice.js

Service usage

To get all cover images from Open Library (ol), Google Books (gb), and Amazon (aws) for several ISBN:

http://coce.server/cover?id=9780415480635,9780821417492,2847342257,9780563533191&provider=ol,gb,aws&all

This request returns:

{
  "2847342257": {
    "aws": "http://ecx.images-amazon.com/images/I/51LYLJRtthL._SL160_.jpg"
  },
  "9780415480635": {
    "gb": "http://bks3.books.google.com/books?id=Yc30cofv4_MC&printsec=frontcover&img=1&zoom=1",
    "aws": "http://ecx.images-amazon.com/images/I/41G7N7fSFvL._SL160_.jpg"
  },
  "9780821417492": {
    "gb": "http://bks5.books.google.com/books?id=3vTqJ6ecRMIC&printsec=frontcover&img=1&zoom=1&edge=curl",
    "aws": "http://ecx.images-amazon.com/images/I/417jg7TjvYL._SL160_.jpg"
  },
  "9780563533191": {
    "ol": "http://covers.openlibrary.org/b/id/2520432-M.jpg",
    "gb": "http://bks0.books.google.com/books?id=OphMAAAACAAJ&printsec=frontcover&img=1&zoom=1",
    "aws": "http://ecx.images-amazon.com/images/I/412CFNG0QEL._SL160_.jpg"
  }
}

Without the &all parameter, the same request returns first URL per ISBN, by provider order:

http://coce.server/cover?id=9780415480635,9780821417492,2847342257,9780563533191&provider=ol,gb,aws

returns:

{
  "2847342257": "http://ecx.images-amazon.com/images/I/51LYLJRtthL._SL160_.jpg",
  "9780415480635": "http://bks3.books.google.com/books?id=Yc30cofv4_MC&printsec=frontcover&img=1&zoom=1",
  "9780821417492": "http://bks5.books.google.com/books?id=3vTqJ6ecRMIC&printsec=frontcover&img=1&zoom=1&edge=curl",
  "9780563533191": "http://covers.openlibrary.org/b/id/2520432-M.jpg"
}

By adding a callback JavaScript function to the request, Coce returns its result as JSONP:

http://coce.server/cover?id=9780415480635,9780821417492,2847342257,9780563533191&provider=ol,gb,aws&callback=populateImg

return:

    populateImg({"2847342257":"http://ecx.images-amazon.com/images/I/51LYLJRtthL._SL160_.jpg","9780415480635":"http://bks3.books.google.com/books?id=Yc30cofv4_MC&printsec=frontcover&img=1&zoom=1","9780821417492":"http://bks5.books.google.com/books?id=3vTqJ6ecRMIC&printsec=frontcover&img=1&zoom=1&edge=curl","9780563533191":"http://covers.openlibrary.org/b/id/2520432-M.jpg"})

Client-side usage

See sample-client.html for a Coce sample usage from JavaScript. It uses coceclient.js module, which is use like this:

// isbns is an array of ISBNs
var coceClient = new CoceClient('http://coceserver.com:8080', 'ol,aws,gb');
coceClient.fetch(isbns, function(isbn, url) {
  $('#isbn_'+isbn).html('<img src="+url)+'"");
});

Performance

coce is highly scalable. With all requested URLs in cache, ab test, 10000 requests, with 50 concurrent requests:

ab -n 10000 -c 50 http://localhost:8080/cover?id=9780415480635,97808?1417492,2847342257,9780563533191&provider=gb,aws

gives this result:

Document Path:          /cover?id=9780415480635,97808?1417492,2847342257,9780563533191
Document Length:        295 bytes

Concurrency Level:      50
Time taken for tests:   7.089 seconds
Complete requests:      10000
Failed requests:        0
Write errors:           0
Total transferred:      4610000 bytes
HTML transferred:       2950000 bytes
Requests per second:    1410.70 [#/sec] (mean)
Time per request:       35.443 [ms] (mean)
Time per request:       0.709 [ms] (mean, across all concurrent requests)
Transfer rate:          635.09 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    1   0.5      1       3
Processing:     9   34  16.5     32     288
Waiting:        7   29  16.4     27     278
Total:         12   35  16.5     34     290

Percentage of the requests served within a certain time (ms)
  50%     34
  66%     34
  75%     37
  80%     39
  90%     44
  95%     50
  98%     54
  99%     58
 100%    290 (longest request)