Varnish minus VCL?

Poul-Henning Kamp phk at
Tue Sep 25 08:16:35 CEST 2007

In message <29f77e8a0709241712k2092c712u6fa3e7844f7ea52 at>, "Luke 
Macpherson" writes:
>I am looking to deploy varnish in a configuration which has a large
>number of backends, and integrate it with our existing management
>infrastructure. I'd like to solicit your opinions on the best way to
>do that.
>What I'm thinking of doing is using replacing the compiled VCL
>configuration object with a custom-written object. This C library
>could talk to our existing infrastructure to keep track of live
>backends and choose the appropriate one at run-time based on
>availability, load and other factors.

VCL has a mechanism for including C language, so in theory you can
do that from a VCL program.

>Is this a reasonable approach? Is the VCL api stable and well-defined
>enough? Is there a better place to plug-in this kind of functionality?

VCL doesn't guarantee stable internal APIs, that's one of the reasons
why we go to such great lengths to make it one single executable that
contains everything.

That said, I don't see anything very hard or impossible in what
you are proposing, but it takes a good programmer to get it right.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

More information about the varnish-dev mailing list