Hello,
I am having a concept question about how the Read/Write process transaction works within the DB network structure.
Assume I have an environment of one master DB with three slaves running Slony-I replication server.
As you all know Slony is a Single master to multiple slaves replication system supporting cascading and slave promotion. Master DB can do both read and write, but the slaves can only do read and for reporting purpose.
Here is the question of concept that I don't understand, if you have answer or provide me a link to referral is appreciated.
Q: For application Developer write codes to accessing the DB server to getting/modify datas. Since there is only one server that can handle both Read/Write which is the Master and slave is only to retrive data.
How should the developer know which DB server should they connecting to for either to read or to write? If developer is using the same fixed connection strings to a fix IP to Master server for Read/Write and another connection string to a fix IP to (for example) my SLAVE1 server to retrive datas.
How and what would happen if my SLAVE1 failed or due to maintaince that I need to replace it?
Also what would happen for Master DB if issues such as failover or switch over that I need to replacing the master server due to failure or for maintaince, or to promote one of the slave to master?
I just need answer that tells me how PostgreSQL and Slony would react if such issues happens. Answer can simply just to provide me a web link for me to read further. Thanks!