Hi, Sujatha! On Mar 22, sujatha wrote: > On 21/03/21 8:21 pm, Sergei Golubchik wrote: > > Hi, Sujatha! > > > > Could you split this patch, please? > > Sure. > > > > 1. Just add replication_applier_status_by_worker table. With > > CHANNEL_NAME column and (perhaps, not sure if it applies) with > > WORKER_ID column. Without extra columns and backup. > > Reason for not including CHANNEL_NAME and WORKER_ID is, multi-source > based parallel replication is bit different in MySQL. > > Please find the following information. > > ==> https://dev.mysql.com/doc/refman/5.7/en/replication-channels.html > > A multi-source replica can also be set up as a multi-threaded > replica, by setting the slave_parallel_workers system variable to a > value greater than 0. When you do this on a multi-source replica, each > channel on the replica has the specified number of applier > threads, plus a coordinator thread to manage them. You cannot configure > the number of applier threads for individual channels. > > In case of MySQL, worker threads are dedicated to particular channel. > > In MariaDB "The pool of replication worker threads is shared among all > multi-source master connections, and among all replication domains that > can replicate in parallel using out-of-order". > > Because of this I didn't include CHANNEL_NAME. In MariaDB Slave_worker > thread's don't have WORKER_ID they only have 'thread_id'.
Okay, thanks May be it'd still make sense to keep CHANNEL_NAME, for the connection name the worker is currently working for? Even if the pool is shared, at any given moment in time the worker can apply a transaction only from some specific connection, right? > > 3. Add backup. > > > > With these three commits you'll have exactly the same diff as now, just > > split (and with CHANNEL_NAME column). > > > > But really, I wonder whether this backup functionality is needed at all? > > In MySQL there is persistent information about these workers, it doesn't > > go away when they're stopped, it's stored persistently in a table, > > indexed by worker_id. If we don't have anything persistent like that and > > all workers completely disappear into oblivion, then, may be, > > replication_applier_status_by_worker should not show anything when they > > aren't running? > > MySQL doesn't persist the worker information in a table. When workers > are stopped due to an error or STOP SLAVE, worker information is > copied(backup) and it is retained till next START SLAVE. Please find > following snippets. Well, there is mysql.slave_worker_info, it's persistent. Regards, Sergei VP of MariaDB Server Engineering and [email protected] _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
