Announcing SPDY support
Today we're announcing SPDY protocol support for your AppHarbor applications. SPDY is an experimental protocol pioneered by Google which is designed to minimize latency of web pages. It is available immediately on all shared and dedicated load balancers in the US and EU regions. Among other things it allows for efficient use of available bandwidth by multiplexing concurrent streams over a single TCP connection and compressing HTTP headers. Here's an example of SPDY in action from last year's Google I/O:
The performance benefits that can be realized with SPDY of course depends on your application and user demographic. If your web pages include many resources (javascript, css, images etc) served directly from your domain you'll likely see some pretty significant performance improvements in supported browsers. For instance, SPDY can eliminate the need for CSS sprites as all images can be downloaded in parallel. If you use a CDN the performance benefits will be limited as the resources fetched externally won't be served through SPDY (unless the CDN supports it). You'll also need to use HTTPS since SPDY relies on SSL. AppHarbor offer piggyback, SNI and IP-based SSL to help you with that.
Chrome and newer versions of Firefox and Opera supports SPDY and it seems like Internet Explorer 11 will support it too. AppHarbor supports draft 2 of the SPDY protocol. We also recommend reading the SPDY white paper and this CloudFlare blog post to learn more about SPDY.
To enable SPDY on an existing application simply click the button on your application's settings page. SPDY is enabled by default on all new applications. Since the protocol and the nginx implementation we use are still considered experimental it'll continue to be configurable for a while.
You can test your application on SPDYCheck.org or you can install the SPDY indicator for Chrome or Firefox to confirm that SPDY is enabled.
Update (May 29, 2013): SPDY is temporarily disabled on shared load balancers while we investigate a configuration issue.