Hello,
I am considering using HAProxy to build an HA system where HAProxy instances are used to forward SQL
queries to a MySQL cluster with a master-master configuration.
I went through an old email of Willy, see http://www.formilux.org/archives/haproxy/1003/3259.html,
but still could not clarify some doubts I have.
1 - Regarding HAProxy availability, I have successfully tried keepalived, however it does not
prevent split-brain scenarios, e.g., all HAPRoxy instances may decide to take the floating IP
address they share. Would you recommend using pacemaker instead?, I would be willing to sacrifice
availability in order to ensure 100% consistency.
2 - Regarding the MySQL farm, I would like writes to be sent to only one server due to the use of
auto-increment within MySQL transactions. I am aware that the "backup" keyword in the haproxy
configuration can be used to achieve that, however I would like to have "stickyness", i.e., once the
failover has occurred, I do not want the failed node to be promoted as "master" whenever it becomes
available, as long as the "backup" is up and running.
3 - Is it possible to perform custom checks/operations? e.g., in order to prevent accidental
modifications I would like all MySQL nodes apart from the "active" one to be in read only mode, see
http://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_super_read_only, and
change that *only* when the backup is promoted.
Thanks,
Michele
