Varnish 5.0 changes to defaults
geoff at uplex.de
Mon Dec 7 15:05:13 CET 2015
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On 12/07/2015 02:30 PM, Rubén Romero wrote:
> While on the topic of changing defaults, I think we should include
> Surrogate-Control and ESI parsing in to the builtin VCL as
> discussed yesterday.
> This was discussed last year:
> So we now need to follow-up on that and the discussions during VUGX
> last week.
The conversations we've had in the past were more about using
Surrogate-Control to set TTLs that are targeted to the proxy, but not
for downstream caches. I believe we never got further than "yes we
should have that, and a VMOD should do it" -- partially my fault, I
should add in fairness.
I didn't want to get nitpicky about this at VUG, but there's a bit of
a problem with Varnish adding Surrogate-Control:ESI/1.0 to the backend
request header (whether by default or not), since Varnish does not in
fact support the full 1.0 ESI spec -- only the include and remove
tags. If the idea is that backends are informed that they can use ESI
in their responses, either for Varnish or, say, a CDN that might use
another proxy, "ESI/1.0" would suggest that the backends can use ESI
tags that Varnish would ignore.
If we really want to do this, the tag might have to be something like
"ESI/Varnish" or "ESI/include&remove" or "VESI/x.y". (There's a
precedent for the latter -- Oracle Web Cache uses "ORAESI/x.y.z".)
Of course, by the time we get to 5.0, fetch processors might be far
enough along that the full ESI spec could be supported (but if so, I
suspect that it will be left to a VMOD, which of course could also
take care of generating Surrogate-Control headers).
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