[Varnish] #1057: Varnish 3.0.2-streaming stops forwarding requests

Varnish varnish-bugs at varnish-cache.org
Thu Nov 10 15:58:34 CET 2011

#1057: Varnish 3.0.2-streaming stops forwarding requests
 Reporter:  hidi      |       Owner:  martin   
     Type:  defect    |      Status:  new      
 Priority:  normal    |   Milestone:           
Component:  varnishd  |     Version:  3.0.2    
 Severity:  major     |    Keywords:  streaming
Changes (by martin):

  * owner:  => martin


 I think I've figured out why you are seeing this now.

 I am guessing you have configured the minimum number of threads at 1?
 Either through parameters or the -w option to varnishd?

 What is happening is that for the streaming code to work, the original
 thread handling the request gets put to do the backend fetch, and the
 request is rescheduled to another thread. The thread handling code in
 varnish will then see that there is no immediate idle thread available,
 and also since the queue of sessions waiting to be served is less than
 thread_pool_add_threshold (another parameter), no new thread is created at
 this time to serve the request. You will probably see that the request
 would be served if some more traffic is thrown at the system.

 A workaround for this until I can make a proper fix could be to set the
 thread_pool_add_threshold parameter to 0.

 Also note that you should probably have a higher minimum number of
 threads. The centos package defaults here are too low.


Ticket URL: <https://www.varnish-cache.org/trac/ticket/1057#comment:4>
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