What is Railgun?

What is Railgun?

Railgun delivers content 730% faster.

We’ve had many questions about Railgun, so let’s jump right into what it’s all about and how it can dramatically increase your website speed.

Railgun is a WAN optimization technology that we offer our hosting customers in partnership with a company called CloudFlare. Railgun technology greatly speeds up the delivery of non-cached pages. While we automatically caches 65% of the resources needed to make up a page, 35% can’t be cached because the resources are dynamically generated or marked as ‘do not cache’. That 35% is often the initial HTML of the page that must be downloaded first. Railgun speeds this remaining 35%.

Railgun opens a secure, tunneled connection between the CloudFlare network and our origin server where the connection only sends differences from the last request. This is similar to how video encoding works.

The markup of websites does not change that frequently from one request to the next. Instead of transferring the entire request between CloudFlare and our servers, Railgun will transfer only the changes in markup from one request to the next. This cuts down on bandwidth, transfer time, and overall page load times. Railgun caches these differences in memory to make page processing as fast as possible.

Railgun uses a delta compression technique that recognizes that even dynamically-generated or personalized pages change only a little over time or between users. Railgun uses that compression technique to greatly reduce the amount of data that is sent over the Internet to our data centers from backend web servers. The result is faster delivery of the critical HTML that the browser must receive before it can download the rest of the page.

Testing with Railgun showed that very large compression ratios were possible and they resulted in a large speedup in page delivery. Notice below the compression ratio that Railgun provides.

One obvious question is to ask how much improvement Railgun can bring to a web site. To work that out you need to know two numbers: the page load time (call it p) and the time to download the initial HTML (call that h). Both values can be obtained from the Developer view in Safari or Chrome or from Firebug.

Railgun will be able to decrease time h. Using the figures above the median improvement would be 70% so you’d expect a page that takes p seconds to load to take roughly p – 0.3 * h with Railgun. Let’s say p is 1.83s and h is 0.949s. The formula would give a Railgun page load time of 1.83 – 0.3 * 0.949 = 1.55s (the actual value 1.15s because Railgun did better than the median for that particular page).

In general, the larger the initial HTML the more Railgun can help. Very small pages won’t require many round trips between the origin server and Railgun edge server, but larger pages will benefit from the delta compression. And Railgun helps when the web browser and origin server are far apart (for example, when a web site is accessed from around the world, Railgun will help eliminate the round trip time between a web surfer in one country and a web server in another).

Common Questions

  • What kind of sites can use Railgun? Any website can benefit from the performance improvements Railgun offers, especially dynamic sites.
  • What much does Railgun cost? We are offering Railgun to our customers who purchase a Business hosting package or above.
  • How do I enable Railgun on my site? Railgun is automatically enabled for all Business plans and above. No server knowledge, code changes, or technical knowledge required.
  • What if I’m having issues enabling Railgun? If you experience issues when enabling Railgun, please contact us here.

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