Unlock the Full Potential of HTTP Caching

Thuva Tharma | Developer @ theScore Inc. | @ttharma

RFC 2616, Section 13

So How Do We Go About Achieving This Goal?

HTTP Request/Response Headers

  > GET /thescore_logo.png
  > If-Modified-Since: Tue, 10 Aug 2013 03:51:19 GMT
  > If-None-Match: "5ee39d70f536014bdb599c1442d"

  < 200 OK
  < ...
  < Cache-Control: max-age=300
  < Expires: Tue, 10 Sep 2013 03:56:19 GMT
  < Last-Modified: Tue, 10 Sep 2013 03:51:19 GMT
  < Etag: "3bbe876fc7acb81cfe03b925fa142710"
          

Expiration: Eliminating the Need to Send Requests

This reduces network round-trips

  > GET /thescore_logo.png

  < 200 OK
  < Cache-Control: max-age=300
  < Expires: Tue, 10 Sep 2013 03:56:19 GMT
          

Validation: Eliminating the Need to Send Full Responses

This reduces network bandwidth

Last-Modified Validator

  > GET /thescore_logo.png

  < 200 OK
  < Last-Modified: Tue, 10 Sep 2013 03:51:19 GMT
          

  > GET /thescore_logo.png
  > If-Modified-Since: Tue, 10 Sep 2013 03:51:19 GMT

  < 304 Not Modified
  < Last-Modified: Tue, 10 Sep 2013 03:51:19 GMT
          

Etag Validator

  > GET /thescore_logo.png

  < 200 OK
  < Etag: "3bbe876fc7acb81cfe03b925fa142710"
          

  > GET /thescore_logo.png
  > If-None-Match: "3bbe876fc7acb81cfe03b925fa142710"

  < 304 Not Modified
  < Etag: "3bbe876fc7acb81cfe03b925fa142710"
          

Combining Expiration & Validation

  > GET /thescore_logo.png

  < 200 OK
  < Cache-Control: max-age=300
  < Etag: "3bbe876fc7acb81cfe03b925fa142710"
          

  > GET /thescore_logo.png
  > If-None-Match: "3bbe876fc7acb81cfe03b925fa142710"

  < 304 Not Modified
  < Cache-Control: max-age=300
  < Etag: "3bbe876fc7acb81cfe03b925fa142710"
          

Non-Browser Clients

If you're developing a mobile application, use a library that takes care of the caching bits for the HTTP client library that you're using:

• iOS: NSURLCache (drop-in caching for NSURLConnection)
• Android: HttpResponseCache (drop-in caching for HttpUrlConnection)

Gateway Caches

Gateway caches or reverse proxy caches let you take advantage of HTTP caching on server-side

Let's see what happens when you put a gateway cache between the client and the server

Nate makes the first request

Roel makes a request after 30 seconds

Mark makes a request after 2 minutes

Geo-Distributed Gateway Caches

Reduce network latency for your clients by distributing the gateway caches geographically

Discussion: How to Come Up with Effective Expiration & Validation Values

Thank You!

thuva.github.com/http_caching