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

[Andrew Beekhof]

On 11/04/2013, at 6:33 AM, Brian J. Murrell <brian at interlinx.bc.ca> wrote:

> 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

no

> or does it properly only send
> exactly the update to the CIB for the operation it's trying to achieve?

correct

> 
> Cheers,
> b.
> 
> 
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