Hi all,
MariaDB Server features a nice-looking interface for reporting progress on long-running SQL operations:
https://mariadb.com/kb/en/mariadb/progress-reporting/MySQL 5.7 implemented something similar for reporting progress for ALTER TABLE…ALGORITHM=INPLACE. I should reimplement that for MariaDB using the existing MariaDB infrastructure.
I wonder if the same interface could be used for tracking progress on periodic background tasks that might not be directly related to the execution of any SQL statements. InnoDB has a number of background tasks, such as:
* purging unneeded history (removing undo log records and delete-marked index records)
* rolling back recovered transactions (mainly, if the server was killed)
* index defragmentation, encryption key rotation
* redo log checkpoints (flush all dirty pages up to the checkpoint LSN; most interesting at shutdown)
The above would need to be monitored also while the server is shutting down. I understand that at startup, we would probably need a different progress reporting interfaces for the very first InnoDB task of redo log apply. Everything else can be done in the background while the server is accepting connections.
Related to this, I wonder if it is possible or feasible to change the SQL layer logic so that at shutdown, it will not issue ROLLBACK (as part of KILL QUERY) to the currently active connections, but let the subsequent startup do the rollback in the background. This should allow faster shutdowns and restarts.
Best regards,