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Improve streaming range responses #3872
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This is an enhanced fix for varnishcache#1777
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Very nice and tidy!
FYI this new logic conflicts with the refactor in the pending #3859. |
At quick glance it shouldn't be a conflict too hard to solve, thank you for pointing it out. |
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bugwash: we need to study the effect on HTTP/1 framing closely.
Without a known The potentially new case is that the response processes less bytes than indicated by varnish-cache/bin/varnishd/cache/cache_range.c Lines 51 to 64 in eec2a6b
It probably needs to be patched so that the request doesn't fail when |
Amended my PR with a patch to not error on short ranges. FYI, the logic in |
After a brief look at 535a5f0, I come to the same nice and tidy conclusion. You even went the extra mile and found a disabled test case that you rehabilitated. I missed this when I first reviewed this directly on Github and I just noticed after a first pass in my proper work environment. FYI we have lined up 3 reviewers to comb this pull request. |
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It has taken me several partial attempts but I finally managed an almost complete review. I couldn't find anything wrong and I'm confident this is a solid change. We often get very good contributions but this one checks all my marks and then more.
Thank you again!
The last thing I need to do what I mentioned above in #3872 (comment) but I would rather adapt my work after merging this one.
Bugwash: OK. |
Opportunity noticed during the review of #3872.
This is a proper fix for #1777 so that it doesn't sometimes deliver
200
responses to range requests. This is achieved by simply not adding acontent-length
header to streaming responses. With this fix the response just contains less bytes than thecontent-range
range would indicate, which is a valid response when the complete-length is unknown as indicated by/*
.FYI, returning less bytes than the
content-range
indicates is exploited in RFC 8673. Incidentally, this patch makes Varnish partially support such streaming range responses.I have re-enabled the disabled tests from #1777, and revised all streaming range tests to expect
206
responses.Background
I am using varnish to cache requests to a backend that delivers Low-Latency HLS. This includes a mode, where parts are delivered using byte range requests from the containing segments. Besides requiring byte-range support, this mode also requires the server to deliver data using streaming range responses. When I tried to deliver individual parts using byte range requests, Varnish failed to work and delivered a full segment in response to
range
requests (response code200
).