New to MySQL scaling-how to have 2 master-write servers?

From what I learned, a MySQL MASTER server is one that can both read and write. Correct?

My questio开发者_开发技巧n is: Suppose you have 2 MySQL master-write servers (and many slave-read servers).

How can you solve the problem of auto-increment? How do you sync it? Suppose you are writing to both the Master1 and Master2...how will you sync it so that the auto-increment is consistent? Can someone please explain the solution to this in a simple sense.

You set server #1 to use odd numbered auto increment values and server number #2 to use even numbered.

# server 1 
auto_increment_increment 2                                
auto_increment_offset    1   

# server 2
auto_increment_increment 2                                
auto_increment_offset    2

There's a linux how-to which outlines the process. See also MySQL docs on this.

Gaps should be okay if your system doesn't need it to be. As soon as you hit the limit of INT or BIGINT you should be ready with a data warehousing setup so you can offload your old data and get ready rollover back to the base offset values. On a write-intensive application, you'll need to be prepared and be able to offload old data as soon as possible.