Request coalescing and other reasons to use Varnish as origin shield

It’s now time to go one step beyond

  • request 1 would like the data to be compressed using gzip (accept-encoding: gzip)
  • request 2 only wants the last 10 bytes of data (range: bytes -10)
  • request 3 is only interested in the metadata of the URL (HEAD)
  • request 4 asks for the first 512 bytes, and would like them compressed with brotli (accept-encoding: brotli, range: bytes 0-511)
  • set the method to GET to grab the full object.
  • unset the range header, for the same reason.
  • force the accept-encoding header to gzip or brotli to save bandwidth and cache space.
  • shared secret in a header: possibly the simplest of them all, we just need to check that a header has the right value
  • JWT: this one is getting popular thanks to a simple standard, easy technologies to pick up and the ability to sign or encrypt using a symmetric or asymmetric key
  • custom tokens: they are legion, but they’re almost all about extracting some data from the request (which Varnish was born to do) combined with a signing mechanism (easy to do with the right VMOD). This means that we can integrate virtually any token with just a few lines of configuration.
  • IP ACL: it’s an oldie but goodie; we just need to check the client IP against one or more IP range, and deny access if we don’t get a match.
  • reverse-DNS: a new trick up Varnish’s sleeve, it’s now able to reverse-lookup an IP and make sure it matches a list of trusted domains. It’s generally used for bot validation, but it’s also valuable here when ACL won’t do because of dynamic IPs.
  • External API: after all, we don’t need to do everything ourselves, and we can ask a third-party API endpoint to validate the request for us. And of course, we can cache the response to save time the next time it pops up.
  • powerful and sensible default behavior is key to performance
  • customization is an integral part of the experience to cover new and highly specific cases




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Varnish Software

Varnish Software

Varnish Software is the world’s leading provider of open source web application acceleration software.

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