[Varnish] #188: thread pileup

Varnish varnish-bugs at projects.linpro.no
Tue Dec 11 12:24:50 CET 2007

#188: thread pileup
 Reporter:  steinove  |        Owner:  phk  
     Type:  defect    |       Status:  new  
 Priority:  high      |    Milestone:       
Component:  varnishd  |      Version:  1.1.1
 Severity:  normal    |   Resolution:       
 Keywords:            |  
Changes (by phk):

  * owner:  des => phk
  * component:  build => varnishd


 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.



Ticket URL: <http://varnish.projects.linpro.no/ticket/188#comment:1>
Varnish <http://varnish.projects.linpro.no/>
The Varnish HTTP Accelerator

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