On Thu, Oct 27, 2016 at 10:27 AM, Scott Mead <sco...@openscg.com> wrote:
> > > On 10/27/16 10:12 AM, Joanna Xu wrote: > > We need to keep the data as it is so remving data fold is not feasible. > > If I run "pg_ctl promote" on the slave to make it fail over, this will > break the replication and then clean up the configuration related to > replication. Any feedback? > > Just to [hopefully] clear up some of the confusion.. > > Somewhere I saw you mention 9.1 . Since you're using 9.1, you won't > have any replication slots in use, if you were using replication slots, > then the master server could started to queue up WAL files waiting for > that node to come back. This could cause you to run out of disk space. > If you were using a replication slot, you would need to (after > promotion) connect to the master and drop it: > - SELECT * FROM pg_replication_slots; > - SELECT pg_drop_replication_slot(slot_name); > > https://www.postgresql.org/docs/9.4/static/functions-admin.html#FUNCTIONS- > REPLICATION > https://www.postgresql.org/docs/9.4/static/catalog-pg- > replication-slots.html > > Again, since you're on 9.1, this doesn't matter, BUT, it's important to > keep in mind for the future. > > If you are using pure streaming replication, there is nothing that needs > 'clean-up' on the master. Doing a promote will indeed do what you want > to accomplish (NB: See below if you are also archiving your WAL). > > That being said, many setups of streaming will also include WAL > (pg_xlog) archiving (check the archive_mode and archive_command in your > postgresql.conf on the master). If you have configured archiving, > chances are, you will have some sort of cleanup job on the slave that > deals with old archived logs. You would either > > A. Want to stop archiving (for the node you are promoting) > B. Ensure that cleanup is still taking place > > These steps are not done for you when you promote a slave, it's > something that you need to deal with yourself. > > There is one other thing to keep in mind. If you are promoting a > database, it's going to become read-write. I would make sure to either > erect a firewall around the promoted slave or edit your pg_hba.conf file > to reject traffic from your applications. If, for some reason your > application were to connect, you could end up with a split-brain > scenario which would mean that some of your data is in the old master > and some is in the newly promoted slave. This can be very, very > dangerous. As long as you exercise care, you will be fine, it's just an > important point that I've seen haunt people in the past. > > Thanks, > > Joanna > > > > -----Original Message----- > > From: Adrian Klaver [mailto:adrian.kla...@aklaver.com] > > Sent: Wednesday, October 26, 2016 7:50 PM > > To: Michael Paquier <michael.paqu...@gmail.com>; Joanna Xu < > joanna...@amdocs.com> > > Cc: pgsql-general@postgresql.org > > Subject: Re: [GENERAL] Remove Standby (SLAVE) from Primary (MASTER) - > Postgres9.1 > > > > On 10/26/2016 04:43 PM, Michael Paquier wrote: > >> On Wed, Oct 26, 2016 at 11:18 PM, Joanna Xu <joanna...@amdocs.com> > wrote: > >>> I’ve been looking for a procedure (step by step) on how to remove > >>> Standby > >>> (SLAVE) from Primary (MASTER) for Postgres9.1 in google and the > >>> archived postings, but no luck. > >> Standby and master servers are two separate Postgres instances. So if > >> you would like to remove a standby from a cluster. You just need to > >> basically stop it, then remove its data folder. And you are done. > >> There is no complicated science here. > > Not sure that is what OP wants. From the original post: > > > > " ... > > 2. After the standby is removed from the primary, both of nodes > > are in standalone configuration. " > > > > > > > > -- > > Adrian Klaver > > adrian.kla...@aklaver.com > > > > This message and the information contained herein is proprietary and > confidential and subject to the Amdocs policy statement, > > you may review at http://www.amdocs.com/email_disclaimer.asp > > > > -- > Scott Mead > Sr. Architect > OpenSCG > > > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general > All you have to do on the slave is: *sudo su postgres* *touch /opt/postgres/9.1/data/trigger'* Then the slave will go to standalone mode./ -- *Melvin Davidson* I reserve the right to fantasize. Whether or not you wish to share my fantasy is entirely up to you.
