Download dies when only metadata for a cached file is present

[mstoykov]

When only the metadata is present and a request for the whole file comes the cache tries a range request with start 0 and length the size of the file. If OK instead of Partial Content is returned the cache handler errors out with no data returned or cached.

Easily reproducible with wget on a still not cached file. Make a request and stop it early enough so that not one piece gets cached and then try to download it again.

$ wget -S -O /dev/null "http://127.0.0.1:8282/cts1.mp4"
--2015-10-16 11:57:12--  http://127.0.0.1:8282/cts1.mp4
Connecting to 127.0.0.1:8282... connected.
HTTP request sent, awaiting response...
  HTTP/1.1 200 OK
  Accept-Ranges: bytes
  Content-Length: 23978230
  Content-Type: video/mp4
  Date: Fri, 16 Oct 2015 08:57:12 GMT
  Last-Modified: Wed, 01 Aug 2012 22:48:29 GMT
  X-Host: 127.0.0.50
  X-Host: 127.0.0.1
Length: 23978230 (23M) [video/mp4]
Saving to: ‘/dev/null’

/dev/null                                                                         2%[====>                                                                                                                                                                                                    ] 671.79K   119KB/s   eta 3m 12s^C
$ #  download it again
$ wget -S -O /dev/null "http://127.0.0.1:8282/cts1.mp4"
--2015-10-16 11:57:39--  http://127.0.0.1:8282/cts1.mp4
Connecting to 127.0.0.1:8282... connected.
HTTP request sent, awaiting response...
  HTTP/1.1 200 OK
  Accept-Ranges: bytes
  Content-Length: 23978230
  Content-Type: video/mp4
  Date: Fri, 16 Oct 2015 08:57:12 GMT
  Last-Modified: Wed, 01 Aug 2012 22:48:29 GMT
  X-Host: 127.0.0.50
  X-Host: 127.0.0.1
Length: 23978230 (23M) [video/mp4]
Saving to: ‘/dev/null’

/dev/null                                                                         0%[                                                                                                                                                                                                         ]       0  --.-KB/s   in 0s

2015-10-16 11:57:39 (0.00 B/s) - Connection closed at byte 0. Retrying.

--2015-10-16 11:57:40--  (try: 2)  http://127.0.0.1:8282/cts1.mp4
Connecting to 127.0.0.1:8282... connected.
HTTP request sent, awaiting response...
  HTTP/1.1 200 OK
  Accept-Ranges: bytes
  Content-Length: 23978230
  Content-Type: video/mp4
  Date: Fri, 16 Oct 2015 08:57:39 GMT
  Last-Modified: Wed, 01 Aug 2012 22:48:29 GMT
  X-Host: 127.0.0.50
  X-Host: 127.0.0.1
Length: 23978230 (23M) [video/mp4]
Saving to: ‘/dev/null’

/dev/null                                                                         0%[                                                                                                                                                                                                         ]       0  --.-KB/s   in 0s

2015-10-16 11:57:40 (0.00 B/s) - Connection closed at byte 0. Retrying.