On 05/08/2017 02:02 AM, Les Green wrote: > Hi All, > > I've recently had an issue when I've needed to add > <resource_name>_mysql_master_IP to hosts in a MySQL HA cluster as I > needed to move a running cluster onto a VPN. > > It seems <resource_name>_REPL_INFO is only set when a resource is > promoted, so as a test, I: > * Put the system in maintenance mode > * Manually removed the <resource_name>_REPL_INFO from the CIB > * Added the appropriate <resource_name>_mysql_master_IP attributes for > each node. > * Manually configured MySQL to be using IP based replication > * Then took the cluster out of maintenance mode. > > The replication continued ok, but as predicted the > <resource_name>_REPL_INFO was not populated. When putting the current > master into standby, the slave was promoted correctly and the > <resource_name>_REPL_INFO populated correctly. > > HOWEVER, while doing this, I noticed in the code, if the master hostname > changes, the replication for the slave is restarted at the master > position, not the slave position. See: > https://github.com/ClusterLabs/resource-agents/blob/master/heartbeat/mysql#L535 > > Why on earth would we ever do this? This seems rife for a disaster of > lost writes. I feel we should only ever be using the current slave > position as the start position for a CHANGE MASTER command. > > Can somebody set me straight on this matter? I feel maybe I'm missing > something significant. > > Cheers, Les
I've never used the mysql agent, but maybe master_log_pos in this case actually stores the slave position in the master log? If not, you might want to open an issue at https://github.com/ClusterLabs/resource-agents/issues Here's the commit that added the relevant code: https://github.com/ClusterLabs/resource-agents/commit/0c07e8655031f161bb8b54683d9fec6ec9a1f29b Interestingly, it says "only 2-node setup is supported". I don't think that's still true, but I don't know what was involved in the change. _______________________________________________ Users mailing list: [email protected] http://lists.clusterlabs.org/mailman/listinfo/users Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
