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Better caching #794

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merged 3 commits into from
Dec 6, 2020
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Better caching #794

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Better caching
elegaanz Jun 25, 2020
719fec0
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elegaanz Jun 25, 2020
d44c034
Merge branch 'main' into better-caching
Dec 6, 2020
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5 changes: 4 additions & 1 deletion src/template_utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,10 @@ impl<'r> Responder<'r> for Ructe {
let etag = format!("{:x}", hasher.finish());
if r.headers()
.get("If-None-Match")
.any(|s| s[1..s.len() - 1] == etag)
// This check matches both weak and strong ETags
// NGINX (and maybe other software) sometimes sends ETags with a
// "W/" prefix, that we ignore here
.any(|s| s[1..s.len() - 1] == etag || s[3..s.len() - 1] == etag)
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can one of you two explain what this does?

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this should probably get it's comment actually.
We send Etags as 'some_tag', the old match does not verify the ', but check that whatever in-between is the right tag. Nginx apparently change the Etag to W/'some_tag', W/ indicating it's a weak Etag, the content may not be byte-equal, but is semantically identical (which is imo a shitty but correct interpretation of the RFC, as Nginx send compressed data)

The new match ignore that W/ saying it's a weak etag and so match if Nginx modified the header we sent previously

Comment might looks like : // if a strong or weak etag matches

{
Response::build()
.status(Status::NotModified)
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