[Varnish] #188: thread pileup
Varnish
varnish-bugs at projects.linpro.no
Fri Jan 11 18:44:57 CET 2008
#188: thread pileup
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Reporter: steinove | Owner: phk
Type: defect | Status: assigned
Priority: high | Milestone:
Component: varnishd | Version: 1.1.1
Severity: normal | Resolution:
Keywords: |
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Comment (by frekri):
Replying to [comment:1 phk]:
> My best diagnosis, is that the backend is very slow for some particular
popular object.
>
> One thread picks it up from the backend and a LOT of requests gets
parked on the busy object until it comes back from the backend.
>
> Once it comes back, all the parked requests gets reinjected and causes
the thread explosion.
>
> Some kind of pacing algorithm is obviously called for, the trick is to
find one that doesn't need too many carefully tweaked numbers to work
generally and reliably.
>
> Thinking...
>
> /phk
On Nettby.no varnish crash almost every day. We run 4 varnish servers.
After I read your post I moved all objects with high traffic to lighttpd
and objects with less traffic to varnish. In total these objects had a lot
of traffic.
On each server we had 1100 hits/s before the last crash today. Before the
crash we had increased iowait, but hits and everything else were normal.
--
Ticket URL: <http://varnish.projects.linpro.no/ticket/188#comment:5>
Varnish <http://varnish.projects.linpro.no/>
The Varnish HTTP Accelerator
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