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Web Performance Daybook Volume 2 by Stoyan Stefanov

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Chapter 8. Frontend SPOF in Beijing

Steve Souders

I’m at Velocity China in Beijing as I write this article for the Performance Calendar. Since this is my second time to Beijing I was better prepared for the challenges of being behind the Great Firewall. I knew I couldn’t access popular U.S. websites like Google, Facebook, and Twitter, but as I did my typical surfing I was surprised at how many other websites seemed to be blocked.

Business Insider

It didn’t take me long to realize the problem was frontend SPOF (http://www.stevesouders.com/blog/2010/06/01/frontend-spof/)—when a frontend resource (script, stylesheet, or font file) causes a page to be unusable. Some pages were completely blank, such as Business Insider (http://www.businessinsider.com, Figure 8-1).

Firebug’s Net Panel shows that anywhere.js is taking a long time to download because it’s coming from platform.twitter.com – which is blocked by the firewall. Knowing that scripts block rendering of all subsequent DOM elements, we form the hypothesis that anywhere.js is being loaded in blocking mode in the HEAD. Looking at the HTML source, we see that’s exactly what is happening:

<head>
...
<!-- Twitter Anywhere -->
<script src="https://platform.twitter.com/anywhere.js?id=ZV0...&v=1"
        type="text/javascript"></script>
<!-- / Twitter Anywhere -->
...

</head>

<body>
The dreaded “blank white screen” due to a blocking Twitter script

Figure 8-1. The dreaded “blank white screen” due to a blocking Twitter ...

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