Open Stack

On 05/19/2014 02:32 PM, sridhar basam wrote:
> On Mon, May 19, 2014 at 1:30 PM, Jay Pipes <jaypipes at gmail.com
> <mailto:jaypipes at gmail.com>> wrote:
>
>     Stackers,
>
>     On Friday in Atlanta, I had the pleasure of moderating the database
>     session at the Ops Meetup track. We had lots of good discussions and
>     heard important feedback from operators on DB topics.
>
>     For the record, I would not bring this point up so publicly unless I
>     believed it was a serious problem affecting a large segment of
>     users. When doing an informal survey of the users/operators in the
>     room at the start of the session, out of approximately 200 people in
>     the room, only a single person was using PostgreSQL, about a dozen
>     were using standard MySQL master/slave replication, and the rest
>     were using MySQL Galera clustering. So, this is a real issue for a
>     large segment of the operators -- or at least the ones at the
>     session. :)
>
>
> ​We are one of those operators that use Galera for replicating our mysql
> databases. We used to  see issues with deadlocks when having multiple
> mysql writers in our mysql cluster. As a workaround we have our haproxy
> configuration in an active-standby configuration for our mysql VIP.
>
> I seem to recall we had a lot of the deadlocks happen through Neutron.
> When we go through our Icehouse testing, we will redo our multimaster
> mysql setup and provide feedback on the issues we see.

Thanks very much, Sridar, much appreciated.

This issue was raised at the Neutron IRC meeting yesterday, and we've 
agreed to take a staged approach. We will first work on documentation to 
add to the operations guide that explains the issues (and the tradeoffs 
of going to a single-writer cluster configuration vs. just having the 
clients retry some request). Later stages will work on a non-locking 
quota-management algorithm, possibly in conjunction with Climate, and 
looking into how to use coarser-grained file locks or a distributed lock 
manager for handling cross-component deterministic reads in Neutron.

Best,
-jay