I'm caching dynamically generated pages (PHP-FPM, NGINX) and have varnish in front of them, this works very well.

However, once the cache timeout is reached, I see this:

• new client requests page
• varnish recognizes the cache timeout
• client waits
• varnish fetches new page from backend
• varnish delivers new page to the client (and has page cached, too, for the next request which gets it instantly)

What I would like to do is:

• client requests page
• varnish recognizes the timeout
• varnish delivers old page to the client
• varnish fetches new page from backend and puts it into the cache

In my case it's not site where outdated information is such a big problem, especially not when we're talking about cache timeout from a few minutes.

However, I don't want punish user to wait in line and rather deliver something immediate. Is that possible in some way?

To illustrate, here's a sample output of running siege 5 minutes against my server which was configured to cache for one minute:

HTTP/1.1,200,  1.97,  12710,/,1,2013-06-24 00:21:06
...
HTTP/1.1,200,  1.88,  12710,/,1,2013-06-24 00:21:20
...
HTTP/1.1,200,  1.93,  12710,/,1,2013-06-24 00:22:08
...
HTTP/1.1,200,  1.89,  12710,/,1,2013-06-24 00:22:22
...
HTTP/1.1,200,  1.94,  12710,/,1,2013-06-24 00:23:10
...
HTTP/1.1,200,  1.91,  12709,/,1,2013-06-24 00:23:23
...
HTTP/1.1,200,  1.93,  12710,/,1,2013-06-24 00:24:12
...

I left out the hundreds of requests running in 0.02 or so. But it still concerns me that there are going to be users having to wait almost 2 seconds for their raw HTML.

Can't we do any better here?

(I came across Varnish send while cache , it sounded similar but not exactly what I'm trying to do.)