[openstack-dev] [nova] Distributed locking

Devananda van der Veen devananda.vdv at gmail.com
Fri Jun 13 00:29:36 UTC 2014

Ironic has a simple lock mechanism for nodes to ensure that, if the
hash ring rebalances while an operation is in progress, the second
conductor doesn't trample on the work that the first conductor is
doing until it's finished (and releases the lock).

Right now, it's got a simple DB backing. We've discussed making it
more pluggable. I'd be all for there being a common openstack way to
do this, preferably in oslo.

/me adds tooz to my list of things to read


On Thu, Jun 12, 2014 at 9:46 AM, Jay Pipes <jaypipes at gmail.com> wrote:
> On 06/12/2014 10:35 AM, Julien Danjou wrote:
>> On Thu, Jun 12 2014, Matthew Booth wrote:
>>> We have a need for a distributed lock in the VMware driver, which I
>>> suspect isn't unique. Specifically it is possible for a VMware datastore
>>> to be accessed via multiple nova nodes if it is shared between
>>> clusters[1]. Unfortunately the vSphere API doesn't provide us with the
>>> primitives to implement robust locking using the storage layer itself,
>>> so we're looking elsewhere.
>> The tooz library has been created for this purpose:
>>    https://pypi.python.org/pypi/tooz
>>    https://git.openstack.org/cgit/stackforge/tooz/
>>> Although I haven't worked through the detail, I believe lock and unlock
>>> would be implementable in all 3 of the current service group drivers.
>>> Fencing would be implemented separately.
>> The plan is to leverage tooz to replace the Nova service group drivers,
>> as this is also usable in a lot of others OpenStack services.
> This is news to me. When was this decided and where can I read about it?
> Thanks,
> -jay
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