We want to move from using MySQL on an EC2 instance to RDS and setup replication. Seems like a no-brainer, right? Well, I've got 30,000 databases to move (don't ask). While setting up replication seems to work well, the process of getting the 30,000 databases into RDS is a royal pain; it takes forever and something almost alway happens.
The nightly backup takes about two hours. I end up with a multi-GB SQL dump file. When I try to restore it, something almost always goes wrong: the RDS instance wasn't big enough memory-wise and crashed, the localhost ran out of swap space, the network connection went flaky. Whatever! I did get it to restore once; IIRC it took 23 hours (30K MySQL DBs are a ton of file IO).
So today, I decided to use mydumper. It generated 30,000 schema files for the database in about two hours, then suddenly, the source MySQL went into uninterruptible sleep according to top, I lost my client connections, strace showed it was still trying to read files, and the mydumper process crashed. I restarted the whole process and just checked the status; mysqld restarted 2.5 hours into it for some reason.
So here's what I'm thinking and I'd like your input: I write two python scripts: firstScript.py will run mydumper on a single database, update a status table, package up the SQL, put it onto an AWS SQS queue, repeating until no more databases are found; the secondScript.py reads from the queue, runs the SQL and updates the status table, repeating until no more messages are found.
I think this can work. Do you? The main thing I'm not sure of is this: can I simply run multiple secondScript.py by Ctrl-Z-ing them into the background?
Or does someone have a better way of moving 30,000 databases?
