jaekyung oh created TS-1955:
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Summary: read_while_writer sends wrong response for range request.
Key: TS-1955
URL: https://issues.apache.org/jira/browse/TS-1955
Project: Traffic Server
Issue Type: Bug
Reporter: jaekyung oh
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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