Summarizing what I've learned.

1.  This problem ONLY affects Bacula Director 9.6.5.  Running a 9.6.5
Director with every other daemon 9.6.3 is sufficient to trigger the bug.
 Running a 9.6.3 Director with everything else 9.6.5 is sufficient to
prevent it.

2.  With Director 9.6.5, the hung-job bug occurs regardless of whether
Galera auto-increment control is in use, even if Bacula is connecting
directly to a single node without using HAproxy, even if the cluster is
brought down to a single node (i.e. Galera not active).  With Director
9.6.3, the bug does NOT occur even when Bacula DB connections are
load-balanced across the cluster using HAproxy, even if auto-increment
control is off.

3.  The bug occurs with 9.6.5, and not with 9.6.3, using the exact same
*build* of MariaDB.


To me, this strongly points to a bug introduced into the Director or the
MySQL driver between 9.6.3 and 9.6.5.  However, I have looked at the
code changes  from 9.6.3 to 9.6.5, but have not been able to spot a
"smoking gun".  I don't see a single change that looks to me as though
it would have an impact.


I ran for a couple of weeks with dird 9.6.5 with every possible measure
to prevent DB conflicts and still got hung jobs.  Then I rolled ONLY the
Director back to 9.6.3 again and rolled back the DB connection config to
what I'd been using for the past [mumble] years, and have not seen a
single hung job in the last 12 days.

I'm getting nowhere trying to narrow this down any further.  If anyone
who knows and understands the codebase better than I do would care to
look at the code diffs from 9.6.3 to 9.6.5 in the context of the stack
traces I've been able to provide, it would be much appreciated.  I've
done all I can to troubleshoot this and I am unable to point a finger to
any particular piece of code, but the evidence that this is a regression
in Director 9.6.5 looks pretty damning to me.



-- 
  Phil Stracchino
  Babylon Communications
  ph...@caerllewys.net
  p...@co.ordinate.org
  Landline: +1.603.293.8485
  Mobile:   +1.603.998.6958


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