On Sat, Jan 15, 2011 at 23:32, Dimitri Fontaine <dimitri@2ndquadrant.fr> wrote:
> Magnus Hagander <magnus@hagander.net> writes:
>> Here's a cutdown version of the idea about including WAL in the base
>> backup. What I initially wanted was to introduce a way to guarantee
>> that the required WAL (with some sort of cutoff of course) would be
>> available for the backup, but I ran out of time for that. We can
>> always add that later.
>
> What if you start a concurrent process that begins streaming the WAL
> segments just before you start the backup, and you stop it after having
> stopped the backup. I would think that then, the local received files
> would be complete. We would only need a program able to stream the WAL
> segments and build WAL files from that… do you know about one? :)
Sure, if you stream the backups "on the side", then you don't need
this feature. This is for "very simple filesystem backups", without
the need to set up streaming of archiving.
If you're streaming the WAL separately, you'd use pg_basebackup in
non-wal mode. That's why it's optional.
>> For now, you need to set wal_keep_segments to make it work properly,
>
> That's quite a big foot gun, isn't it? You would have to at least offer
> an option to check for your backup or to call it broken when you miss
> some WAL files on the server.
Oh, it will give you an ERROR if any of the required WAL files aren't
around anymore. So you will know that your backup is incomplete.
> The only other safe option I know about that's not a pg_streamrecv
> subprocess would be to require archiving for the duration of the base
> backup, but I think we agreed that it would be nice being able to bypass
> that.
No, the safe option I'm envisioning for this one is to just prevent
the server from recycling the logfiles until they have been sent off.
Witha cap so we don't prevent recycling forever if the client hangs.
This is the part I started working on, but didn't hav etime to finish
for the CF. I've not given up on it, it's just waiting for later.
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
