Open Stack

On 05/20/2014 10:07 AM, Jay Pipes wrote:
> 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
>
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Am late to this topic, but wanted to share this in case anyone wanted to 
read further on this behavior with galera - 
http://www.mysqlperformanceblog.com/2012/08/17/percona-xtradb-cluster-multi-node-writing-and-unexpected-deadlocks/

--
patrick