Unset before variable set

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Alex G

• September 28, 2017 10:18

Reading the guide for Delivering different content to different devices, I noticed that the suggested VCL does the following:

  unset req.http.X-UA-Device;
  unset req.http.X-UA-Vendor;

  set req.http.X-UA-Device = "desktop";
  set req.http.X-UA-Vendor = "generic";

What is the purpose of using unset before set?

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  Alex G

  • October 02, 2017 20:16

  Thanks for your answer, Peter! Didn't know you could have a header twice!

  Wouldn't set zero out any aberrant values by overwriting a new value?

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  Peter Wohlers

  • October 02, 2017 20:51

  If you have shielding set up, VCL will run at both the edge POP as well as the shield POP. and yeah... the unsetting really does fall into the 'paranoia' category, as you are correct...the value would be overwritten :slight_smile:

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  Alex G

  • October 03, 2017 07:22

  Got it! Thanks again, Peter.

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