Testing for Frontend SPOF

Frontend Single Points of Failure (SPOF) can critically impact web performance, given the continuing rise in 3rd-party widgets on pages it is becoming increasingly important as it is causing delays or complete failure in page loading if third-party scripts or resources fail. Identifying and mitigating these risks is essential for maintaining a resilient website.

WebPageTest simulates failure of specified domains by rerouting requests to blackhole.webpagetest.org, which silently drops all traffic. A blackhole server behaves as expected when testing the failure mode for third-party widgets.

Steps to Test

Using SPOF Tab

Enter all hosts that you want to fail against your test and hit start test.

Using Scripting

• Initial Test: Test the site as you normally would, ensuring the "capture video" option is enabled. It's also helpful to label the test for easy identification.
• Script for Failure Simulation: To capture the broken version of the site, use a script to reroute the domains to the blackhole server and then navigate to the page you want to test. Here's an example script:

setDnsName ajax.googleapis.com blackhole.webpagetest.org 
setDnsName apis.google.com blackhole.webpagetest.org 
setDnsName www.google-analytics.com blackhole.webpagetest.org 
setDnsName connect.facebook.net blackhole.webpagetest.org 
setDnsName platform.twitter.com blackhole.webpagetest.org 
navigate your.url.com 

Paste the script into the script box, ensure "capture video" is checked.

• Comparing Results: Go to the test history, select the tests you ran, and click compare. Logging into the site before submitting tests helps organize your history.