We want to get an idea of the amount of Range requests we currently receive as a percentage of the total.
The data-gathering procedure should only include meaningful Range requests. For example, Range: bytes=0- is not a particularly interesting one, as it ends up requesting the whole file. Same goes for Range: bytes=0-N for a file of length N+1.
Finally, we want to find out what percentage of those are high-range requests beyond some bytes cutoff (say 32M).
| Project | Branch | Lines +/- | Subject | |
|---|---|---|---|---|
| operations/puppet | production | +18 -36 | cache_upload backend: convert range requests into pass |
I've collected 30 minutes of frontend GET requests on cp1048 as follows:
varnishncsa -m 'RxRequest:GET' -F '%{Range}i %{Content-Length}o %r' -n frontendOut of 1029692 total requests we got:
| norange | 1026679 | 99.71% of total |
| range | 3012 | 0.29% of total |
| sillyrange | 540 | 17.93% of range |
| highrange | 10 | 0.33% of range |
Numbers obtained with:
/^- / { norange++ }
/^bytes=/ { range++ }
/^bytes=[3-9][2-9][0-9][0-9][0-9][0-9][0-9][0-9]/ { high++ }
/^bytes=0- / { silly++ }
/^bytes=0-[0-9]/ && $1 ~ "bytes=0-"$2-1 { silly++ }
END {
print "Total " NR
printf "|norange |%7d|%.2f%% of total\n", norange, norange * 100 / NR
printf "|range |%7d|%.2f%% of total\n", range, range * 100 / NR
printf "|sillyrange |%7d|%.2f%% of range\n", silly, silly * 100 / range
printf "|highrange |%7d|%.2f%% of range\n", high, high * 100 / range
}Note that for some media file types, such as Ogg (the container format), it's impossible to know the file's duration in seconds from the header of the file. Browsers that want to show the file's duration in their little duration bar deal with this by seeking at the end of the file with a Range header.
Until recently, the workaround was to send the X-Content-Duration header, which we precalculate and store in Swift. Mozilla has deprecated this since Firefox 41, though, so the original behavior of seek-to-end might apply again.
Unlike most of the web, we used to have most of our media in Ogg/Ogv, as it was the only unencumbered format. In the days before WebM it was very common to see these kinds of Range requests on the upload varnishes. X-Content-Duration support in MediaWiki/Swift was added per our request exactly for avoiding these annoyingly expensive Ranges.
These days there's WebM, so hopefully Ogg/Ogv usage has declined. More data about this would be probably be useful, though, especially in light of the recent Firefox 41 changes.
This is a 24 hours sample collected on hosts in ulsfo, eqiad and esams.
cp4005 - Total 123158948
| norange | 122827836 | 99.73% of total |
| range | 331004 | 0.27% of total |
| sillyrange | 61451 | 18.57% of range |
| highrange | 3054 | 0.92% of range |
cp1048 - Total 97091403
| norange | 96825644 | 99.73% of total |
| range | 265584 | 0.27% of total |
| sillyrange | 84313 | 31.75% of range |
| highrange | 1776 | 0.67% of range |
cp3034 - Total 154112575
| norange | 153814761 | 99.81% of total |
| range | 297688 | 0.19% of total |
| sillyrange | 81431 | 27.35% of range |
| highrange | 4142 | 1.39% of range |
Change 304802 had a related patch set uploaded (by Ema):
cache_upload backend: convert range requests into pass