Open Stack

On 10/09/2018 04:34 AM, Christian Berendt wrote:
> 
> 
>> On 8. Oct 2018, at 19:48, Jay Pipes <jaypipes at gmail.com> wrote:
>>
>> Why not send all read and all write traffic to a single haproxy endpoint and just have haproxy spread all traffic across each Galera node?
>>
>> Galera, after all, is multi-master synchronous replication... so it shouldn't matter which node in the Galera cluster you send traffic to.
> 
> Probably because of MySQL deadlocks in Galera:
> 
> —snip—
> Galera cluster has known limitations, one of them is that it uses cluster-wide optimistic locking. This may cause some transactions to rollback. With an increasing number of writeable masters, the transaction rollback rate may increase, especially if there is write contention on the same dataset. It is of course possible to retry the transaction and perhaps it will COMMIT in the retries, but this will add to the transaction latency. However, some designs are deadlock prone, e.g sequence tables.
> —snap—
> 
> Source: https://severalnines.com/resources/tutorials/mysql-load-balancing-haproxy-tutorial

Have you seen the above in production?

-jay