On 10/09/2018 04:34 AM, Christian Berendt wrote:

On 8. Oct 2018, at 19:48, Jay Pipes <jaypi...@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:

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.


Have you seen the above in production?


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