On 07/03/2016 08:49 AM, Andy Colson wrote:
> On 07/03/2016 10:35 AM, Adrian Klaver wrote:
>> On 07/03/2016 08:06 AM, Andy Colson wrote:
>>> Hi all,
>>>
>>> I have a master (web1) and two slaves (web2, webserv), one slave is
>>> quite far from the master, the db is 112 Gig, so pg_basebackup is my
>>> last resort.
>>>
>>> I followed the page here:
>>> https://www.postgresql.org/docs/9.5/static/pgupgrade.html
>>>
>>> including the rsync stuff. I practiced it _twice_, once in PG 9.5 beta,
>>> and again a week ago, on two VM's I created locally. Both practice
>>> sessions worked perfect.
>>>
>>> I just ran it on the live databases. The master seems ok, its running
>>> PG 9.5 now, I can login to it, and no errors in the log.
>>>
>>> Neither slave works. After I'd gotten done with the pgupgrade steps,
>>> both slaves gave me this error:
>>>
>>> FATAL: database system identifier differs between the primary and
>>> standby
>>>
>>> Sure enough pg_controldata show'd their database system id different
>>> (all three web1, web2, webserv were different. no matches at all), so
>>> I'm assuming the rsync didnt rsync right, or I missed a step and ran it
>>> to early, or something ... I'm not quite sure.
>>>
>>> I needed to get the live website back up and running again, so I let the
>>> master go, ran analyze, and when it was finished, used the steps here to
>>> try and resync:
>>>
>>> https://wiki.postgresql.org/wiki/Binary_Replication_Tutorial
>>>
>>> on Master:
>>> select pg_start_backup('clone',true);
>>> rsync -av --exclude pg_xlog --exclude postgresql.conf /pub/pg95/*
>>> web2:/pub/pg95/
>>> select pg_stop_backup();
>>> rsync -av /pub/pg95/pg_xlog web2:/pub/pg95/
>>
>> Not sure about above rsync, that seems to undo what you did previously.
>>
>> Also was the remote directory empty when you did this?
>>
>
> Not sure what you mean by undo. pgupgrade.html page, step 10, has you
> rsync the master to the slave, so the pg95 directory is hard linked to
> the pg93, which save's a ton to bandwidth when your servers are cross
> county.
I understand I am just trying to figure out what mixing methods
(pg-upgrade, pg_start_backup) is doing?
In particular the section on pg_start_backup:
https://www.postgresql.org/docs/9.5/static/continuous-archiving.html#BACKUP-LOWLEVEL-BASE-BACKUP
starts with:
"Ensure that WAL archiving is enabled and working."
and from I gather that is not the case.
>
> My second rsync did the same thing, but only on the pg95 directory (my
> db lives in /pub/pg95).
>
> No, the directory was not empty, and I'm really trying to avoid a fresh
> copy of 112 Gig.
>
> -Andy
>
>
>
--
Adrian Klaver
adrian.klaver@aklaver.com