Thanks for writing this article, it was great and gave a lot of insights I couldn't find anywhere else. I have a question regarding the circular replication recovery though. When you demonstrate the two node recovery using the events, you use the change master command, and specify not only the host, but the log file and position as well. Then in the 4 node example, you only specify the host. Are the log files important? If so how can you get the values?
I'd expect that if you don't specify the log values then it would start at the beginning, and that this would be a problem in the fall over.