[Varnish] #642: log buffer (VSL) can get corrupted

[Varnish]

#642: log buffer (VSL) can get corrupted
------------------------+---------------------------------------------------
 Reporter:  Tv          |       Owner:  phk  
     Type:  defect      |      Status:  new  
 Priority:  normal      |   Milestone:       
Component:  varnishlog  |     Version:  trunk
 Severity:  normal      |    Keywords:       
------------------------+---------------------------------------------------
 I had varnishd behave oddly, didn't really manage to debug fully but got
 reports of delays in serving. "varnishlog" showed no new entries even if I
 knew it was serving. "varnishlog -d" ended with

 {{{
     0 Backend_health - linkubate_api[2] Still healthy 4--X-S-RH 8 3 8
 0.001422 0.001540 HTTP/1.0 200 OK
     0 Backend_health - pix
 13357 (null)       - -X-S-RH 8 3 8 0.001592 0.001526 HTTP/1.0 200 OK
 29556 (null)       - art
 24946 ObjStatus    - t
 }}}

 which looked like corruption. Even with varnishd shut down, "varnishlog
 -d" behaved the same. I removed the /var/lib/varnish/$HOSTNAME/_.vsl file,
 started varnishd again, and everything went back to normal.

 Unfortunately, I don't have a copy of the corrupted file. It may have been
 corrupted by a kernel/virtualization bug.

 Wouldn't it make sense for varnishd to not trust the old file contents
 when it starts up?

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Ticket URL: <http://varnish-cache.org/ticket/642>
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