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

[Andrew Beekhof]

On Fri, Feb 22, 2013 at 5:18 AM, Brian J. Murrell <brian at interlinx.bc.ca> wrote:
> I wonder what happens in the case of two racing "crm" commands that want
> to update the CIB (with non-overlapping/conflicting data).  Is there any
> locking to ensure that one crm cannot overwrite the other's change?
> (i.e. second one to get there has to read in the new CIB before being
> able to apply his change and send it back)  Or if there is a situation
> where one write stomps another's,

If my information is up-to-date, yes.

crmsh uses a read+modify+replace cycle, if B reads after A has read
but before the replace has happened, data will be lost.

> is there at least some kind of
> notification?

i dont think so

> Ultimately, it would be bad for two nodes for example to issue:
>
> # crm node attribute $(uname -n) set name value
>
> at the same time and have one of those updates lost.
>
> But that's what I think I am seeing.
>
> Cheers,
> b.
>
>
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