[Varnish] #1506: Backend replies with 'Content-Length' but varnish 4.0 discards and replies with 'Transfer-Encoding: chunked'

[Varnish]

#1506: Backend replies with 'Content-Length' but varnish 4.0 discards and replies
with 'Transfer-Encoding: chunked'
---------------------------------+----------------------
 Reporter:  DonMacAskill         |       Type:  defect
   Status:  new                  |   Priority:  normal
Milestone:  Varnish 4.0 release  |  Component:  build
  Version:  4.0.0                |   Severity:  critical
 Keywords:                       |
---------------------------------+----------------------
 Nils Goroll suggested I open this ticket, so here goes.  Using Varnish 4,
 I have a set of backends that're responding with a valid ''Content-
 Length'' header and no ''Transfer-Encoding'' header.

 On the first hit from a client, rather than responding to the client with
 those headers, Varnish is dropping the ''Content-Length'' header and
 adding ''Transfer-Encoding: chunked'' to the response. (Interestingly, the
 payload doesn't appear to have any chunks in it - it's one contiguous
 payload).

 This causes serious problems for clients like Flash video players that are
 trying to do segment-size, bandwidth, etc analysis based on the ''Content-
 Length'' header. Their analysis fails, and they can't do things like
 multi-bitrate streaming, etc.

 I've tried a number of semi-obvious things like:

 * beresp.do_stream = true/false
 * beresp.do_gzip = false
 * beresp.do_esi = false
 * unset req.http.Accept-Encoding

 Sample backend response:

 {{{
 HTTP/1.1 200 OK
 Cache-Control: public, max-age=600
 Content-Type: video/mp4
 Date: Tue, 13 May 2014 19:44:35 GMT
 Server: Apache
 Content-Length: 796618
 Connection: keep-alive
 }}}

 Sample varnish response:

 {{{
 HTTP/1.1 200 OK
 Server: Apache
 Cache-Control: public, max-age=600
 Content-Type: video/mp4
 Date: Tue, 13 May 2014 23:10:06 GMT
 X-Varnish: 2
 Age: 0
 Transfer-Encoding: chunked
 Accept-Ranges: bytes
 }}}

 Subsequent loads of the object do including the Content-Length header,
 just not the first load into cache.

 VCL: https://gist.github.com/onethumb/e64a405cc579909cace1

 varnishlog output: https://gist.github.com/onethumb/e66a2bc4727a3a5340b6

 Stackoverflow discussion:  http://stackoverflow.com/questions/23643233
 /how-do-i-disable-transfer-encoding-chunked-encoding-in-varnish

-- 
Ticket URL: <https://www.varnish-cache.org/trac/ticket/1506>
Varnish <https://varnish-cache.org/>
The Varnish HTTP Accelerator