Just use 'master_slave_adapter' in your database.yml:
production: adapter: master_slave_adapter real_adapter: mysql master: database: app_production username: rails password: ******** host: masterdb.example.com slave: database: app_production username: rails password: ******** host: slavedb.example.com
- No matter what, all "write" calls go to the master.
- Inside transactions, all calls go to the master.
- Inside Observers, all calls go to the master.
By default, all other "read" calls will go to the slave, unless you add "default: master" to the options in database.yml.
If you want to control when the slave is used, you can specify which server you want to use (for the 'read' calls) by using:
TheModel.with_master do ... end
TheModel.with_slave do ... end
A lot of inspiration and understanding of the problem came from Rick Olsen's Masochism.
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