Re: Streaming replication: rsync to switchover

On 04/19/2011 02:11 PM, Ray Stell wrote:
> On Tue, Apr 19, 2011 at 11:16:08AM +0200, rudi wrote:
>> On 04/19/2011 10:09 AM, Gerhard Hintermayer wrote:
>> So you keep the old pg_xlog
>
> the admin book says to exclude old pg_xlog
>

Which book is this?

So I guess something like this (from new master to former master) should
be safe:

$ psql -c "SELECT pg_start_backup('switchover base backup')"
$ rsync -av /var/lib/postgresql/9.0/main/ --delete --exclude server.crt
--exclude server.key --exclude recovery.* --exclude postmaster.pid
--exclude archive $FORMER_MASTER_ADDRESS:/var/lib/postgresql/9.0/main/
$ psql -c "SELECT pg_stop_backup()"

What about the archiving directory of the former slave (now master)?
It should be cleaned guess, in case it will be slave again. If I look at
that directory, after a failover it is not empty.
This looks strange to me because pg_cleanup_archive should have already
cleaned it.

BTW, is there any documentation about the logic behind pg_xlog
filenames? It is really obscure and this makes really hard understanding
what's going on. I'm sure that most recent mtime gives me the active
WAL, and I can match somehow this:

Latest checkpoint location:           7/F70021A0
Prior checkpoint location:            7/F7002110
Latest checkpoint's REDO location:    7/F7002168
Latest checkpoint's TimeLineID:       2

with this filename: 0000000200000007000000F7

and that's all.

thanks,

--
rd

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