Is it possible to have mysql treat row based updates as "upserts"? When processing row based replication events, mysql replication will break if it's unable to find a row matching the "before image".

Is there any setting to tell mysql, if you don't find that row, just create it?
Consider using INSERT ... ON DUPLICATE KEY UPDATE or REPLACE statements on the master server.

Just note that:


These are unsafe statements for replication, so statement based replication will produce a warning and divergence is possible - consider using MIXED bin log.
These only work on tables with a single unique key or primary key
If there are differences in auto-increment primary key columns, the statements will update divergent records (hence the unsafe classification) (see the manual)