On Mon, Nov 6, 2023 at 6:36 AM Guillaume Quintard <[email protected]> wrote: > > Hi everybody! > > A bunch of questions I regularly get regarding Varnish behavior revolve > around the built-in vcl, mainly, I get one of these three: > - why is Varnish not caching? > - how come something is happening in vcl_X even though I don't have it in my > vcl? > - what on earth is that built-in vcl you are talking about? > > As usual, I have a half-baked solution with a bunch of problems, which will > hopefully inspire smarter people to fix the issue properly. > > What I came up with is here: > https://github.com/varnish/toolbox/tree/verbose_builtin/vcls/verbose_builtin > Essentially, use std.log() to explain what the built-in code is doing. > > At the moment, it's a purely opt-in solution, meaning that you need to know > about builtin.vcl to find it, which doesn't really help with discoverability, > but I intend on including that code in the docker image, which should raise > awareness a bit. > The absolute best in my mind would be to have something similar in core, but > I can see how importing std would be a hurdle. Maybe as part of packaging, we > could include that file in the provided default.vcl? > > I dismissed the performance penalty of printing a few more lines as > negligible, but I could be wrong about that.
I think we should rather have new VSL tags for the call action in VCL (calling and returning from a non-step subroutine) because this way if they really consume too many resources (vsl_buffer, vsl_space, etc) they could easily be masked. For example: - VCL_sub_call - VCL_sub_return I would probably not log subroutines called by VMODs and leave that as an exercise to VMOD authors. > There's also the question of phrasing, so we can have a message that is > concise but also gives enough information to debug the behavior. But that's > very minor, and the least of our worries here. > > Thoughts? If you look at the VCL reference documentation between 6.0 and 7.4 you may notice that we went from a monolithic manual to a bunch of them: https://varnish-cache.org/docs/6.0/reference/ https://varnish-cache.org/docs/7.4/reference/ One thing I've wanted to do for a while is to add a vcl-builtin(7) manual, and I think even a small synopsis and a dump of bin/varnishd/builtin.vcl would improve discoverability. I would however prefer to have something smarter than that, but haven't given enough thoughts on how to proceed. For example, the vcl-step(7) and vcl-var(7) manual are authoritative, so updating them changes Varnish's behavior. We could imagine having a vcl-builtin(7) manual where we document and put individual subroutines authoritative snippets, and generate bin/varnishd/builtin.vcl from that. Cheers _______________________________________________ varnish-misc mailing list [email protected] https://www.varnish-cache.org/lists/mailman/listinfo/varnish-misc
