On Thu, Feb 03, 2011 at 05:25:48PM +0100, Holger Parplies wrote:
> Hi,
> 
> Robin Lee Powell wrote on 2011-02-02 08:12:47 -0800
> [[BackupPC-users] General questions about the background queue and
> link commands.]:
> > Let me ask some more general questions:  What does the
> > background queue actually *mean*?
> 
> from the source (3.2.0beta0, but probably unchanged):
> 
> #    - @BgQueue is a queue of automatically scheduled backup
> requests.
> 
> If my memory serves me correctly, BackupPC queues each host it
> knows about at each wakeup (presumably unless it's already on a
> queue ... see %BgQueueOn, %CmdQueueOn, %UserQueueOn). It then
> proceeds to process these "backup requests" in the order they're
> in the queue. Most of the time, that will simply mean deciding
> that it's not yet time for the next backup of this host. Now, if
> ...
> 
> > All but one host (!), 226 out of 227, is in the background
> > queue, which seems rather excessive since about half my hosts
> > have recent backups.
> 
> ... I would guess that the first host is currently doing its
> backup, you've got $Conf{MaxBackups} = 1, 

8 actually.

This isn't happening on most of my hosts; only 2 out of 6.

> and most of the queue will simply "disappear" once the running
> backup is finished, because BackupPC will decide for each host in
> turn whether its backup is recent enough.
> 
> Of course, if your situation is that one backup is always running
> (i.e. your BackupPC server is constantly backing up something),
> you'll see this situation most of the time - all of the time if
> backups take more time than the interval between wakeups.

Since it's every 15 minutes, yeah.  :)

> Well, you obviously won't really have that situation - the example
> is just for illustration. But you'll see this (for a possibly
> short period of time) whenever a backup takes longer than the
> wakeup interval, and whenever the first host to be scheduled is
> actually backed up (for the duration of that backup). That is not
> a problem. It is not an indication of "high load".
> 
> To sum it up, that a host is on @BgQueue does *not* necessarily
> mean that a backup will be done for this host, just that a check
> will be done whether a backup is needed. If so, the backup will
> also be done, else it's just the check.
> 
> Note that this also means that backups may start at any time, not
> just at the times listed in the WakeupSchedule (but you've
> probably already noticed that).

Got it.

OK, so the question becomes, how do I monitor for general backup
queue problems?  I've had situations where something gets stuck,
like a nightly job, and the queue gets backed up, and I want to
detect that.

I guess if I could get access to the backup age that's on the host
summary, from a script, that would do.

-Robin

-- 
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