Sorry for the top post (outlook at work). Sounds like you need to prime the 
cache with a script so your clients don't get "first request" syndrome. 

 

Stefan Caunter :: Senior Systems Administrator :: TOPS

e: scaun...@topscms.com  ::  m: (416) 561-4871

www.thestar.com www.topscms.com

 

From: varnish-misc-boun...@varnish-cache.org 
[mailto:varnish-misc-boun...@varnish-cache.org] On Behalf Of Bjarni RĂșnar 
Einarsson
Sent: November-09-10 2:23 PM
To: varnish-misc@varnish-cache.org
Subject: Is Varnish useless with slow/remote back-ends & large files?

 

Hi!

I am attempting to use Varnish in a somewhat unusual fashion, and before I give 
up and drop it for something else, I figured I'd describe my problem here and 
see if there's something I've missed.

What I am doing is implementing a service (http://pagekite.net/) to provide a 
"remote HTTP front-end" for people who want to run webservers off a personal 
computing device (possibly even a mobile device). I've got a nice proxy/tunnel 
solution up and running, and want to add some caching in the front-end to 
lighten the load on the back-end server and more importantly the tunnel to the 
back-end, which may be quite bandwidth constrained.

At the moment it seems Varnish is effectively useless for this, because it 
can't both cache and stream at the same time - it does one or the other, right?

This means when a client downloads a large file, things just hang while the 
whole thing gets transferred (over a slow link) to Varnish, likely even timing 
out. I can't automatically stream it anyway, as the only trick I've seen to 
switch to "pipe" mode for large content is to "restart" based on the 
content-length header, which means the object will be sent twice - doubling the 
load on exactly the link I'm trying to spare. The closest I can get is to 
automatically switch to "pipe" for certain paths based on URL regular 
expressions, which avoids the sloth and timeouts but provides no caching 
benefits and will still do the wrong thing for some large files.

Varnish is quite an awesome piece of software, but I'm getting the feeling that 
it just wasn't designed for my (admittedly unusual) environment. I'd love to be 
proven wrong!

Thanks... :-)

-- 
Bjarni R. Einarsson
The Beanstalks Project ehf.

Making personal web-pages fly: http://pagekite.net/

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