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

[Brian J. Murrell]

On 13-02-21 07:48 PM, Andrew Beekhof wrote:
> On Fri, Feb 22, 2013 at 5:18 AM, Brian J. Murrell <brian-SquOHqY54CVWr29BmMi2cA at public.gmane.org> 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.

Does crm_resource suffer from this problem or does it properly only send
exactly the update to the CIB for the operation it's trying to achieve?

Cheers,
b.


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