Duncan Thomas wrote:
We are working on some sort of distributed replacement for the locks in
cinder, since file locks are limiting our ability to do HA. I'm afraid
you're unlikely to get any traction until that work is done.
I also have a concern that some backend do not handle load well, and so
benefit from the current serialisation. It might be necessary to push
this lock down into the driver and allow each driver to choose it's
locking model for snapshots.
IMHO (and I know this isn't what everyone thinks) but I'd rather have
cinder (and other projects) be like this from top gear (
https://www.youtube.com/watch?v=xnWKz7Cthkk ) where that toyota truck is
virtually indestructible vs. trying to be a high-maintenance ferrari
(when most openstack projects do a bad job of trying to be one). So,
maybe for a time (and I may regret saying this) we could consider
focusing on reliability, consistency, being the toyota vs. handling some
arbitrary amount of load (trying to be a ferrari).
Also I'd expect/think operators would rather prefer a toyota at this
stage of openstack :) Ok enough analogies, ha.
-Josh
On 27 Jun 2015 06:18, "niuzhenguo" <niuzhen...@huawei.com
<mailto:niuzhen...@huawei.com>> wrote:
Hi folks,____
__ __
Currently we use a lockfile to protect the create operations from
concurrent delete the source volume/snapshot, we use exclusive____
locks on both delete and create sides which will ensure that:____
__ __
__1.__If a create of VolA from snap/VolB is in progress, any delete
requests for snap/VolB will wait until the create is complete.____
__2.__If a delete of snap/VolA is in progress, any create from
snap/VolA will wait until snap/VolA delete is complte.____
__ __
but, the exclusive locks will also result in:____
__ __
__3.__If a create of VolA from snap/VolB is inprogress, any other
create requests from snap/VolB will wait until the create is
complete. ____
__ __
So the create operations from same volume/snapshot can not process
on parallel, please reference bp [1].____
I’d like to change the current filelock or introduce a new lock to
oslo.concurrency.____
__ __
Proposed change:____
Add exclusive(write) locks for delete operations and shared(read)
locks for create operations, to ensure that create from
volume/snapshot____
can work on parallel and protect create operations from concurrent
delete the source volume/snapshot.____
__ __
I’d like to get what’s your suggestions, thanks in advance.____
__ __
[1] https://blueprints.launchpad.net/cinder/+spec/enhance-locks____
__ __
__ __
-zhenguo____
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