hanging connections

Kristian Lyngstol kristian at varnish-software.com
Mon Dec 20 09:25:05 CET 2010

On Fri, Dec 17, 2010 at 03:40:35PM +0100, Stig Bakken wrote:
> I have a script processing varnishlog output to give me the serving
> latency based on the ReqEnd tag, and frequently see objects served from
> cache, size around 25kB, that take 5+ seconds to serve.

If there are two requests for an object, request A and request B, the
following will happen:

Time  |    Action
0s    | A asks for /foo
      | Cache-miss - fetch from backend
0.5s  | B asks for /foo
      | Cache hit on busy object - wait for it
5s    | Web server is finished delivering /foo
5.1s  | A gets /foo - cache miss
5.1s  | B gets /foo - cache hit

It's a bit difficult to spot this as it happens, it's been a matter of
discussion recently (Arthur being the one who first became aware of the

It sounds like this might be what you are seeing.

- Kristian
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