Обсуждение: recovery_min_apply-delay and remote_apply
Current PostgreSQL Documentation on recovery.conf has this about recovery_min_apply_delay[1]: ---<--- This parameter is intended for use with streaming replication deployments; however, if the parameter is specified it will be honored in all cases. Synchronous replication is not affected by this setting because there is not yet any setting to request synchronous apply of transaction commits. --->--- If i understand correctly, this is not true anymore with 9.6, where remote_apply will have exactly the behavior the paragraph above wants to contradict: any transaction executed with synchronous_commit=remote_apply will wait at least recovery_min_apply_delay to finish. Given that synchronous_commit can be controlled by any user, this might be dangerous if someone doesn't take care enough. I think we need a doc patch for that at least, see attached patch against master, but 9.6 should have a corrected one, too. [1] <https://www.postgresql.org/docs/devel/static/standby-settings.html> -- Thanks Bernd
Вложения
On Sat, Sep 17, 2016 at 8:45 AM, Bernd Helmle <mailings@oopsware.de> wrote: > Current PostgreSQL Documentation on recovery.conf has this about > recovery_min_apply_delay[1]: > > ---<--- > > This parameter is intended for use with streaming replication deployments; > however, if the parameter is specified it will be honored in all cases. > Synchronous replication is not affected by this setting because there is > not yet any setting to request synchronous apply of transaction commits. > > --->--- > > If i understand correctly, this is not true anymore with 9.6, where > remote_apply will have exactly the behavior the paragraph above wants to > contradict: any transaction executed with synchronous_commit=remote_apply > will wait at least recovery_min_apply_delay to finish. Given that > synchronous_commit can be controlled by any user, this might be dangerous > if someone doesn't take care enough. Yes, I missed that sentence. Thanks. > I think we need a doc patch for that at least, see attached patch against > master, but 9.6 should have a corrected one, too. +1 -- Thomas Munro http://www.enterprisedb.com
On Fri, Sep 16, 2016 at 5:55 PM, Thomas Munro <thomas.munro@enterprisedb.com> wrote: > On Sat, Sep 17, 2016 at 8:45 AM, Bernd Helmle <mailings@oopsware.de> wrote: >> Current PostgreSQL Documentation on recovery.conf has this about >> recovery_min_apply_delay[1]: >> >> ---<--- >> >> This parameter is intended for use with streaming replication deployments; >> however, if the parameter is specified it will be honored in all cases. >> Synchronous replication is not affected by this setting because there is >> not yet any setting to request synchronous apply of transaction commits. >> >> --->--- >> >> If i understand correctly, this is not true anymore with 9.6, where >> remote_apply will have exactly the behavior the paragraph above wants to >> contradict: any transaction executed with synchronous_commit=remote_apply >> will wait at least recovery_min_apply_delay to finish. Given that >> synchronous_commit can be controlled by any user, this might be dangerous >> if someone doesn't take care enough. > > Yes, I missed that sentence. Thanks. > >> I think we need a doc patch for that at least, see attached patch against >> master, but 9.6 should have a corrected one, too. > > +1 Committed with a bit of adjustment, and back-patched to 9.6. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company