Our site has a number of large PDF and MP3 files which we would like to cache in Varnish as static files. Currently we don't do much special - simply remove the cookies in
set resetp.ttl = 100w; in
The problem seems to be when one of these files is requested (maybe by older browsers) and it's not already in the Varnish cache. There is a delay while Varnish downloads the file from the backend. My understanding is that it doesn't start delivering to the client until the data is fully loaded. This may take 20 seconds or so and sometimes Adobe Acrobat or the MP3 plugin get confused.
Is there a way to both
pass the content directly while download and save it in the cache for the next matching client request?