Re: [Engine-devel] Requirement for Locking Mechanism

From: "Yaniv Kaul" <ykaul(a)redhat.com&gt; To: "Michael Kublin" <mkublin(a)redhat.com&gt; Cc: engine-devel(a)ovirt.org Sent: Tuesday, November 29, 2011 12:18:15 PM Subject: Re: [Engine-devel] Requirement for Locking Mechanism On 11/29/2011 12:13 PM, Michael Kublin wrote: > Hi All, > > We are introducing a new short term locking mechanism at engine. > The motivation is races which are occurring between different > flows, the main problem is : > we did not update status of some entity and other flow was started > , which is a main cause for different collisions and situation > which > can not be fixed in appropriate way by engine or vdsm. > The current status is a workaround which is trying to reduce a race > : in many places in the code, there is additional query to DB in > order to check the appropriate status of entity. > The proposed solution is internal locking mechanism - which will > lock an appropriate entity until its status will not be updated in > DB, after that > an internal short term lock will be released. > > The design for locking mechanism can be found here: > http://www.ovirt.org/wiki/Features/DetailedLockMechanism The page still has many remains of the template. > The patch which is introduce an implementation for mechanism can be > found here: http://gerrit.ovirt.org/#change,403 > (Using of new mechanism all around a code and integration with bll > will be sent in the future, including cleaning of workaround) > > Regards Michael > > _______________________________________________ > Engine-devel mailing list > Engine-devel(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/engine-devel There's an implicit assumption that there's only going to be a single active backend working against the database? Y.