March 2017
Beginner
160 pages
3h 15m
English
Content preview from Getting Started with Varnish Cache
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 4. The Varnish Configuration Language
As mentioned before, Varnish is a reverse caching proxy. There are many other reverse proxies out there that do caching, even in the open source ecosystem. The main reason Varnish is so popular is, without a doubt, Varnish Configuration Language (VCL)—a domain-specific language used to control the behavior of Varnish.
The flexibility that VCL offers is unprecedented in this kind of software. It’s more a matter of expressing and controlling the behavior by programming it rather than by declaring it in a configuration file. Because of the rich API that is exposed through the objects in VCL, the level of detail with which you can tune Varnish is second to none.
The curly braces, the semicolon statement endings, and the commenting style in VCL remind you of programming languages like C, C++, and Perl. That’s maybe why VCL feels so intuitive; it sure beats defining rules in an XML file.
The Varnish Configuration Language doesn’t just feel like C, it actually gets compiled to C and dynamically loaded as a shared object when the VCL file is loaded by the Varnish runtime. We can even call it transpiling, because we convert a piece of source code to source code in another programming language.
Note
If you’re curious what the C code looks like, just run the varnishd program with the -C option to see the output.
In this chapter you’ll learn how VCL will allow you to hook into the finite state machine of Varnish to programmatically extend its ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.