[Pacemaker] racing crm commands... last write wins?

[Dejan Muhamedagic]

On Wed, Mar 20, 2013 at 10:40:10AM -0700, Bob Haxo wrote:
> Regarding the replace triggering a DC election ... which is causing
> issues with scripted installs ... how do I determine which crm commands
> will NOT trigger this election?

It seems like every "configure commit" could possible result in
new election. But I'm not sure what does it depend on.

> I need a way of avoiding this election
> while installing.
> 
> I'm finding that when repeating the scripted install with the same
> commands, sometimes the DC election gets triggered and sometimes it does
> not.

With the same configuration updates?

> With the DC election, these messages get logged, followed by the
> whole xml version of the configuration.
> 
> Call cib_replace failed (-62): Timer expired

This is a problem connecting to the cib process, i.e. it's not
related to a configuration update (as it cannot proceed anyway).

> ERROR: 55: could not replace cib
> INFO: 55: offending xml: <configuration>
> 
> Any suggestions for avoiding replacing rather than incrementally
> modifying the configuration?

Not right now. The configuration update process in crmsh needs to
be modified.

Thanks,

Dejan

> Thanks,
> Bob Haxo
> SGI
> 
> 
> 
> On Mon, 2013-03-04 at 17:25 +0100, Lars Marowsky-Bree wrote:
> > On 2013-03-04T17:14:28, Dejan Muhamedagic <dejanmm at fastmail.fm> wrote:
> > 
> > > > Thought so at the time, yes. And I do think it cleaned up a few things,
> > > > we just need to improve it. The full CIB replace also seems to trigger
> > > > an election ...
> > > I think that used to happen in Heartbeat clusters but got fixed
> > > in the meantime, the details are a bit foggy.
> > 
> > No, if you look at the current logs on the DC, you'll also see this
> > happening. I think it's the replace of the node section that triggers
> > it.
> > 
> > 
> > > > Then most of the logic in crmsh would remain unchanged (i.e., it'd still
> > > > operate on whole CIBs only), but the way how it passes it on to
> > > > Pacemaker would improve. I hope.
> > > crmsh currently doesn't keep the original copy of the CIB.
> > 
> > Right, but that should be a simple thing to add and prototype quickly.
> > (Says he who isn't going to be the one doing it ;-)
> > 
> > > Anyway, this approach is worth investigating.
> > 
> > Thanks, let me know how it goes!
> > 
> > 
> > Regards,
> >     Lars
> > 
> 
> 
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