[Varnish] #1119: Varnish 3.0.2 freezed, Pushing vcls failed:#012CLI communication error (hdr)

Varnish varnish-bugs at varnish-cache.org
Mon Sep 3 17:55:15 CEST 2012

#1119: Varnish 3.0.2 freezed, Pushing vcls failed:#012CLI communication error
 Reporter:  campisano                            |       Owner:
     Type:  defect                               |      Status:  closed
 Priority:  normal                               |   Milestone:
Component:  build                                |     Version:  3.0.2
 Severity:  blocker                              |  Resolution:  worksforme
 Keywords:  child died pushing vcls failed       |
  #012CLI communication error (hdr)              |

Comment (by campisano):

 Replying to [comment:12 lampe]:
 > the child blocks on a write to the shared memory file when cached disk
 writes exceed a certain amount and the disk is busy. With large RAM, the
 disk sync can take several seconds. If the child blocks long enough, the
 VCL upload from the master process times out and the child is terminated
 but not restarted.

 > Putting the shm log file on tmpfs resolved it for me. No physical disk,
 thus no waiting on the I/O scheduler. The Varnish Book explicitly
 recommends that the log must not cause physical disk I/O.

 I understand, so the best way appears to use RAM directly or with tempfs.
 But I have not sufficent RAM to give to the varnish log, so what happen
 when varnish want store something and have no more space to write? I
 suppose that he discard something old, do the call to the apache and all
 can work fine, I'm right?

 However, why using tempfs where can use RAM directly? Varnish could have a
 little overhead with tempfs that is not necessary I suppose, or I'm wrong?

 > I'll also experiment with lowering /proc/sys/vm/dirty_background_bytes
 to <1GB and increasing dirty_ratio to 50%. See
 http://www.kernel.org/doc/Documentation/sysctl/vm.txt for a description of
 these linux kernel parameters.

 Nice, but this is for all the process on the server... However, did you
 get good results with this configs (without use tempfs)?

 Thanks you lampe.

Ticket URL: <https://www.varnish-cache.org/trac/ticket/1119#comment:13>
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