Hacker News Reader

Correct me if I'm wrong, but done with a proxy in-between that can "pause" requests, you could have done the move with 0 seconds and no rejected requests, and I don't think mydumper/myloader/xtrabackup matters for that. The "migration" would be spinning up a new database, making it catch up, then switching over. If you can pause/hang in-flight requests while switching, not a single one needs to fail :)

View on HN

The "making it catch up" is the tricky part. You need an initial backup for that. xtrabackup can take that backup "hot" without blocking read/writes. mysqldumper will block writes for whatever time that initial backup takes, for 2TB of data that's going to be hours.

Once you have that initial back up you can set your replica and make it catch up , then you switch. I choose to take the few seconds of downtime doing the switch because for my use case that was acceptable.

Isn't that just a flag? "--lock-tables=false", alternatively --single-transaction for InnoDB.

If you want a consistent backup that you can use to setup a replica you need to block writes while the backup is taken, take the backup while the database is shutdown OR use xtrabackup.

Reply on news.ycombinator.com