Extend Fastly to vary its caching per user-agent: BingBot and GoogleBot and the rest.

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Gulshan Beejan

• May 14, 2020 05:20

Hi,

 

We are trying to implement a new VCL to vary caching based on certain bots. Please see recv VCL as implemented below.

if ( req.http.User-Agent ~ "(?i)(ads|Google|bing|msn|yandex|baidu|ro|career|seznam|)bot" ) 
{
 set req.http.X-UA-Device = "Googlebot";
 set req.http.Vary = " X-UA-Device";
 return(lookup);
   } 

Do you see any issues that could bring a performance impact on the above mentioned?

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• 

  Hiromasa Kakehashi

  • May 14, 2020 07:29
  • Edited

  Hi Gulshan,

  I don't see any issues in Varying on a custom header as you do in the code.
  You just need to set the Vary header in the responses. Here is an example:

  vcl_recv

  if ( req.http.User-Agent ~ "(?i)PATTERN1" ) {
    set req.http.X-UA-Device = "Bot";
  } else if ( req.http.User-Agent ~ "(?i)PATTERN2" ) {
    set req.http.X-UA-Device = "Mobile";
  } else {
    set req.http.X-UA-Device = "Desktop";
  }

  vcl_fetch

  if (beresp.http.Vary) {
    set beresp.http.Vary = beresp.http.Vary "X-UA-Device";
  } else {
    set beresp.http.Vary = "X-UA-Device";
  }

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• 

  Gulshan Beejan

  • May 14, 2020 07:43

  Hi Hiromasa,

   

  Thanks for your reply. We already have a vcl fetch implemented as per your recommendation. I'll apply these on and see how it goes.

   

  Appreciate your help!

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