Support for If-None-Match header.

[Jan Hugo Prins | BetterBe]

Hello,

We are currently investigating the use of Varnish for our
infrastructure. In the software we build, we depend on the If-None-Match
header and the use of ETAG's.
The API we have created creates mainly JSON objects, and they differ in
size from a few hundreds of bytes to several megabytes. A lot of these
JSON objects are perfectly suited for caching, until someone changes a
parameter and this can happen at any moment. That is also why we keep a
record of all ETAG's and we invalidate them when needed.

What we would like to do is cache created JSON object in front of our
production environment and when someone requests the same calculation
that someone else has requested before and the ETAG is still valid, send
out the cached object. But this basicly implies the following workflow:



Somewhere I found an old Trac Wiki document that describes something
like this, but I can't figure out if this has been implemented or not.
https://www.varnish-cache.org/trac/wiki/BackendConditionalRequests?version=8

Could someone tell me if the workflow I describe is possible? My first
tests tell me that in the default setup it isn't working like this.

Best regards,
Jan Hugo Prins


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