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https://issues.apache.org/jira/browse/TS-2314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14153417#comment-14153417
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William Bardwell commented on TS-2314:
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Mode 1 waits even if the start of the range is not present...which certainly is
unfortunate behaviour much of the time...but if the start of the last range is
in cache, then there is no performance benefit (assuming nothing weird) to
tunneling the range request, just waiting would get it just as fast, if not
faster.
(arguably, to optimize further you would want one or more thresholds, since if
you are one byte away from the start of the range it is almost the same as if
you are one byte past the start...so you would want to say "if the first byte
of the highest range is < read_while_write_range_close_limit away, just
wait...")
The degenerate case with mode "2" is that a range request for 0- will never use
an in progress download, when clearly it should...
> New config to allow unsatifiable Range: request to go straight to Origin
> ------------------------------------------------------------------------
>
> Key: TS-2314
> URL: https://issues.apache.org/jira/browse/TS-2314
> Project: Traffic Server
> Issue Type: Bug
> Components: Core
> Reporter: jaekyung oh
> Assignee: Sudheer Vinukonda
> Labels: range
> Attachments: TS-2314.diff
>
>
> Basically read_while_writer works fine when ATS handles normal file.
> In progressive download and playback of mp4 in which moov atom is placed at
> the end of the file, ATS makes and returns wrong response for range request
> from unfulfilled cache when read_while_writer is 1.
> In origin, apache has h264 streaming module. Everything is ok whether the
> moov atom is placed at the beginning of the file or not in origin except a
> range request happens with read_while_writer.
> Mostly our customer’s contents placed moov atom at the end of the file and in
> the case movie player stops playing when it seek somewhere in the movie.
> to check if read_while_writer works fine,
> 1. prepare a mp4 file whose moov atom is placed at the end of the file.
> 2. curl --range xxxx-xxxx http://www.test.com/mp4/test.mp4 1>
> no_cache_from_origin
> 3. wget http://www.test.com/mp4/test.mp4
> 4. right after wget, execute “curl --range xxxx-xxxx
> http://www.test.com/mp4/test.mp4 1> from_read_while_writer” on other terminal
> (the point is sending range request while ATS is still downloading)
> 5. after wget gets done, curl --range xxxx-xxxx
> http://www.test.com/mp4/test.mp4 1> from_cache
> 6. you can check compare those files by bindiff.
> The response from origin(no_cache_from_origin) for the range request is
> exactly same to from_cache resulted from #5's range request. but
> from_read_while_writer from #4 is totally different from others.
> i think a range request should be forwarded to origin server if it can’t find
> the content with the offset in cache even if the read_while_writer is on,
> instead ATS makes(from where?) and sends wrong response. (In squid.log it
> indicates TCP_HIT)
> That’s why a movie player stops when it seeks right after the movie starts.
> Well. we turned off read_while_writer and movie play is ok but the problems
> is read_while_writer is global options. we can’t set it differently for each
> remap entry by conf_remap.
> So the downloading of Big file(not mp4 file) gives overhead to origin server
> because read_while_writer is off.
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