Two-minute Tech Tuesdays - Dynamic Backends

In this episode we'll be looking at dynamic backends. Dynamic backends in Varnish allow backends to be defined on the fly, instead of being predefined. Basically imagine if instead of connecting varnish to one specific origin server, you enable it to connect to different ones as required, say multiple servers.

 

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6/15/21 12:15 AM
by Thijs Feryn

Vmod-goto: your go-to guy for dynamic backends

In Dridi's post, you learned about Varnish's technical choices regarding backends, and why a VMOD was necessary. If you didn't read the article (shame on you), here's the recap:

  • Varnish resolves domain names and IP when compiling the VCL, so the resolved address is set in stone.
  • And there must be exactly one resolved address, if the domain name is not found, or is served by multiple IPs, the VCL won't load.
  • You can work around this with a cron'd script, periodically generating a VCL with the correct and updated addresses.
  • However, this forces you to garbage-collect the old VCL; you'll have to take extra care of the probes and you'll reset the backend stats everytime you reload since backends are tied to the VCL.
  • So we built a VMOD.

And that VMOD is named "named", another proof that engineers shouldn't be allowed to name things.

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11/23/16 1:03 PM
by Guillaume Quintard

Built for speed, Varnish Plus never slows down: Introducing the latest version

 

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11/15/16 2:00 PM
by Annette De Freitas

Varnish Software Blog

The Varnish blog is where our team writes about all things related to Varnish Cache and Varnish Software...or simply vents.

 

 
 

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