Date: Sun, 28 Jan 2018 22:35:49 -0500
From: Bruce Momjian <bruce@momjian.us>
To: Ray Stell <stellr@vt.edu>
Cc: "pgsql-admin@postgresql.org" <pgsql-admin@postgresql.org>
Subject: Re: [ADMIN] standby upgrade questions
Message-ID: <20180129033549.GB11620@momjian.us>
References: <700537e7-9039-0bbd-61fb-b28af635121e@vt.edu>
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On Tue, Oct 17, 2017 at 11:34:51AM -0400, Ray Stell wrote:
> From:   https://www.postgresql.org/docs/9.6/static/pgupgrade.html

Sorry for the late reply.

> Q1 - Is there a procedure to force this "catch up?"   I suppose preventing db
> activity with a pg_hba hack and running "select pg_switch_xlog()."   Maybe
> there's a better way?

Uh, if there was a better way than pg_hba.conf, we would document it. 
Do you have any ideas?

>  1. Prepare for standby server upgrades
> 
>     If you are upgrading standby servers (as outlined in section step 10),
>     verify that the old standby servers are caught up by running pg_controldata
>      against the old primary and standby clusters. Verify that the "Latest
>     checkpoint location" values match in all clusters. (There will be a
>     mismatch if old standby servers were shut down before the old primary.)
> 
>     Also, if upgrading standby servers, change wal_level to replica in the 
>     postgresql.conf file on the new master cluster.
> 
> 
> Q2 - I was wondering what the end result is, in general, of this rsync of old
> and new?  If the old db files and upgraded, new db files are meshed what do you
> get on the other side of the rsync?  Again, I mean in general what is the goal?

I added more detail on what happens with rsync in this commit:

	commit 2d4a614e1ec34a746aca43d6a02aa3344dcf5fd4
	Author: Bruce Momjian <bruce@momjian.us>
	Date:   Tue Sep 12 13:17:52 2017 -0400
	
	    docs:  improve pg_upgrade rsync instructions
	
	    This explains how rsync accomplishes updating standby servers and
	    clarifies the instructions.
	
	    Reported-by: Andreas Joseph Krogh
	
	    Discussion: https://postgr.es/m/VisenaEmail.10.2b4049e43870bd16.15d898d696f@tc7-visena
	
	    Backpatch-through: 9.5

The new text is:

	https://www.postgresql.org/docs/10/static/pgupgrade.html
	
	What this does is to record the links created by pg_upgrade's link mode
	that connect files in the old and new clusters on the primary server. It
	then finds matching files in the standby's old cluster and creates links
	for them in the standby's new cluster. Files that were not linked on the
	primary are copied from the primary to the standby. (They are usually
	small.) This provides rapid standby upgrades. Unfortunately, rsync
	needlessly copies files associated with temporary and unlogged tables
	because these files don't normally exist on standby servers.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +