[Varnish] #1485: Background refetches update the text of the HTTP status line

[Varnish]

#1485: Background refetches update the text of the HTTP status line
---------------------------------+----------------------
 Reporter:  smerrill             |       Type:  defect
   Status:  new                  |   Priority:  low
Milestone:  Varnish 4.0 release  |  Component:  varnishd
  Version:  4.0.0                |   Severity:  minor
 Keywords:                       |
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 Varnish 4 is an excellent release - thank you for everything.

 I have noticed one interesting issue. This example uses background
 refresh, and the simplified VCL is as follows, setting a short TTL for
 HTML pages but a long grace/keep interval to allow conditional background
 refreshes.

 {{{
 sub vcl_backend_response {
   if (beresp.http.Content-Type ~ "text/html" && beresp.ttl > 0s) {
     set beresp.ttl = 1m;
   }
   set beresp.grace = 24h;
   set beresp.keep = 24h;
 }
 }}}

 This works extremely well, but after the backend sends a 304 in response
 to Varnish's conditional backend request, the text of the status line is
 updated to be "HTTP/1.1 200 Not Modified".

 {{{
 $ curl -I -XGET -s http://192.168.168.168/ | egrep '(HTTP|Age)'
 HTTP/1.1 200 OK
 Age: 0

 # Wait about two minutes, hit it again.

 $ curl -I -XGET -s http://192.168.168.168/ | egrep '(HTTP|Age)'
 HTTP/1.1 200 OK
 Age: 132

 # Background conditional request is now triggered, hit it one more time.

 $ curl -I -XGET -s http://192.168.168.168/ | egrep '(HTTP|Age)'
 HTTP/1.1 200 Not Modified
 Age: 5
 }}}

-- 
Ticket URL: <https://www.varnish-cache.org/trac/ticket/1485>
Varnish <https://varnish-cache.org/>
The Varnish HTTP Accelerator