Conditionally Disabling GZIP in Order to Serve ESI

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Andri Antoniades

[Edit: ESI + GZIP can now be supported in certain circumstances. Please contact support@fastly.com to discuss turning this on. Note: You will require a paid account and a TLS product with us in order to do this].

Fastly’s version of Varnish currently doesn’t support the use of ESI with GZIP. But you can conditionally disable GZIP in order to serve ESI when it’s appropriate for your service.

Assuming you’ve already had custom vcl enabled, you’ll then want to insert some ESI logic into the Fastly boilerplate under vcl_fetch.

In this example, we’ll enable ESI based on Content-Type:

sub vcl_fetch {
#FASTLY fetch
  if ( beresp.http.Content-Type ~ "^text/html" ) {
    esi;
  }

Next, you’ll want to add unset bereq.http.accept-encoding to vcl_miss:

sub vcl_miss {
unset bereq.http.accept-encoding;
#FASTLY miss
  return(fetch);
}

Finally, you’ll create a GZIP object in the UI and—based on our example above—remove text/html from the content types to be compressed and the html extension, if it’s there.

These steps should ensure that when you’re not serving ESI, you’re still compressing, but when you are serving ESI, your content remains uncompressed, allowing your ESI content to render consistently.

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  • Frank Farmer

    There's a missing semicolon after unset bereq.http.accept-encoding

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  • Justin

    Thanks @Frank_Farmer

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  • Ilya Kaplan

    Hi Justin,

    I ping with this question every now and then. Is there any plan to fix ESI with GZip limitation? After all Varnish 3 does support it.

    Now question related to workaround mentioned here. Turning gzip off for all HTML would drastically increase content size. Wouldn't it seriously impact on performance of site that uses this workaround?

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  • Justin

    You're in luck! We're almost ready to announce support but not quite yet... If you'd like to test it out in the meantime send in a Support ticket and we can let you the current state.

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  • Justin

    Don't jinx it! :sweat_smile: Seriously though, the release date hasn't been given, but it's being tested by customers now, so it won't be too long...

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  • markwainwright

    Hi @justin. Just wondering if there's any update on when ESI + gzip will be supported?

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  • Justin

    Hi @markwainwright. Enabling will require emailing support@fastly.com. It's fairly quick and easy to do now.

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