On Tuesday, June 18, 2013, Amit Kapila wrote: > On Tuesday, June 18, 2013 12:18 AM Sawada Masahiko wrote: > > On Sun, Jun 16, 2013 at 2:00 PM, Amit kapila > > <amit.kap...@huawei.com<javascript:;> > > > > wrote: > > > On Saturday, June 15, 2013 8:29 PM Sawada Masahiko wrote: > > > On Sat, Jun 15, 2013 at 10:34 PM, Amit kapila > > <amit.kap...@huawei.com <javascript:;>> wrote: > > >> > > >> On Saturday, June 15, 2013 1:19 PM Sawada Masahiko wrote: > > >> On Fri, Jun 14, 2013 at 10:15 PM, Amit Kapila > > <amit.kap...@huawei.com <javascript:;>> wrote: > > >>> On Friday, June 14, 2013 2:42 PM Samrat Revagade wrote: > > >>>> Hello, > > >>> > > >>>>>> We have already started a discussion on pgsql-hackers for the > > problem of > > >>>>>> taking fresh backup during the failback operation here is the > > link for that: > > >>>>>> > > >>>>>> > > >>>>>> http://www.postgresql.org/message-id/CAF8Q-Gxg3PQTf71NVECe- > > 6OzRaew5pWhk7yQtb > > >>>>>> jgwrfu513...@mail.gmail.com <javascript:;> > > >>>>>> > > >>>>>> Let me again summarize the problem we are trying to address. > > >>>>>> > > >>>>>> > > >>>>> How will you take care of extra WAL on old master during > > recovery. If it > > >>>>> plays the WAL which has not reached new-master, it can be a > > problem. > > >> > > >>>> you means that there is possible that old master's data ahead of > > new > > >>>> master's data. > > >> > > >>> I mean to say is that WAL of old master can be ahead of new > > master. I understood that > > >>> data files of old master can't be ahead, but I think WAL can be > > ahead. > > >> > > >>>> so there is inconsistent data between those server when fail back. > > right? > > >>>> if so , there is not possible inconsistent. because if you use GUC > > option > > >>>> as his propose (i.g., failback_safe_standby_mode = remote_flush), > > >>>> when old master is working fine, all file system level changes > > aren't > > >>>> done before WAL replicated. > > >> > > >>> Would the propose patch will take care that old master's WAL is > > also not ahead in some way? > > >>> If yes, I think i am missing some point. > > > > > >> yes it will happen that old master's WAL ahead of new master's WAL > > as you said. > > >> but I think that we can solve them by delete all WAL file when old > > >> master starts as new standby. > > > > > > I think ideally, it should reset WAL location at the point where new > > master has forrked off. > > > In such a scenario it would be difficult for user who wants to get a > > dump of some data in > > > old master which hasn't gone to new master. I am not sure if such a > > need is there for real users, but if it > > > is there, then providing this solution will have some drawbacks. > > > I think that we can dumping data before all WAL files deleting. All > > WAL files deleting is done when old master starts as new standby. > > Can we dump data without starting server? > > Sorry I made a mistake. We can't it.
this proposing patch need to be able to also handle such scenario in future. Regards, --- Sawada Masahiko -- Regards, ------- Sawada Masahiko
