Thanks, Karl. It's pretty shocking that this kind of severe limitation isn't disclosed and only pointed out in the comments, and that this was the selected cluster design in the first place. I don't understand how anyone could use this in production.
Sincerely, Artem -- Founder, Android Police <http://www.androidpolice.com>, APK Mirror <http://www.apkmirror.com/>, Illogical Robot LLC beerpla.net | @ArtemR <http://twitter.com/ArtemR> On Wed, Aug 12, 2020 at 1:44 PM Karl Levik <karl.le...@gmail.com> wrote: > Hi Artem, > > As far as I know based on reading release notes, and in my experience as a > MariaDB Galera user: Yes, this is still the case. Although more and more > types of ALTER TABLE statements are now done "online", i.e. they run with > algorithm=INPLACE | NOCOPY | INSTANT so the table doesn't have to be > re-built, and therefore they don't necessarily result in the kind of > long-running, cluster-blocking operations we had in the past. > > Still, it would have been nice if there was a way to avoid > cluster-blocking by DDL in the cases where ALTER TABLE still doesn't run > "online". > > Regards, > Karl > > > On Wed, 12 Aug 2020 at 21:11, Artem Russakovskii <archon...@gmail.com> > wrote: > >> Hi, >> >> I haven't received a reply to this one. Is someone on the team with >> knowledge of the cluster able to comment? >> >> Thanks. >> >> Sincerely, >> Artem >> >> -- >> Founder, Android Police <http://www.androidpolice.com>, APK Mirror >> <http://www.apkmirror.com/>, Illogical Robot LLC >> beerpla.net | @ArtemR <http://twitter.com/ArtemR> >> >> >> On Tue, Apr 21, 2020 at 4:15 PM Artem Russakovskii <archon...@gmail.com> >> wrote: >> >>> Hi, >>> >>> On this page >>> https://mariadb.com/kb/en/mariadb-galera-cluster-known-limitations/, a >>> user in 2017 pointed out the following: >>> >>> >>> 3 years, 3 months ago Björn Schneider >>> <https://mariadb.com/kb/user/id/4916> >>> Schema changes of large tables in Galera >>> <https://mariadb.com/kb/en/mariadb-galera-cluster-known-limitations/#comment_2704> >>> >>> You should be warned that every DDL statement executed on a Galera >>> cluster will per default BLOCK the complete cluster (not only the table, or >>> even just the database the table resides in)! This is the default "Total >>> Order Isolation" (TOI) mode. >>> >>> The DDL statements can't be killed - once issued, it will run until >>> completed or an error occurs. >>> >>> Issuing e.g. a column-altering DDL statement on a large table will take >>> the complete cluster out of commission until every node has completed the >>> migration. Only some operations (e.g. changing DEFAULT values) are always >>> short-timed and won't interefere with the cluster's opperations. >>> >>> Long-running, cluster-blocking DDL are of course a no-go on a productive >>> system. To resolve this issue, there are several resulutions; Percona, for >>> example, provides a script to "online" migrate a table >>> (pt-online-schema-change), or you can use the "Rolling Schema Upgrade" >>> (RSU) for data-compatible changes. More about that in the Galera >>> documentation. >>> >>> In my opionion, this behaviour should definitely added as "observation" >>> to this page - it's definitely not something you'd expect coming from a >>> "normal" MariaDB/MySQL system. >>> >>> >>> We're considering moving to a cluster environment from a 1 master - 3 >>> slave configuration that has proven inflexible, but such a severe >>> limitation seems unusable in production. >>> >>> Is this still the case in 2020? What is the reasoning behind such an >>> architectural decision, if so? >>> >>> Thank you. >>> >>> Sincerely, >>> Artem >>> >>> -- >>> Founder, Android Police <http://www.androidpolice.com>, APK Mirror >>> <http://www.apkmirror.com/>, Illogical Robot LLC >>> beerpla.net | @ArtemR <http://twitter.com/ArtemR> >>> >> _______________________________________________ >> Mailing list: https://launchpad.net/~maria-discuss >> Post to : maria-discuss@lists.launchpad.net >> Unsubscribe : https://launchpad.net/~maria-discuss >> More help : https://help.launchpad.net/ListHelp >> >
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