Обсуждение: Re: [COMMITTERS] pgsql: If recovery_target_timeline is set to 'latest' and standby mode

On Mon, Mar 7, 2011 at 20:16, Heikki Linnakangas
<heikki.linnakangas@iki.fi> wrote:
> If recovery_target_timeline is set to 'latest' and standby mode is enabled,
> periodically rescan the archive for new timelines, while waiting for new WAL
> segments to arrive. This allows you to set up a standby server that follows
> the TLI change if another standby server is promoted to master. Before this,
> you had to restart the standby server to make it notice the new timeline.

Can we make recovery_target_timeline='latest' the default when we are
in standby mode? That would suddenly make it a lot easier to "repoint
a slave" after a switchover...

--
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/

On 07.03.2011 21:20, Magnus Hagander wrote:
> On Mon, Mar 7, 2011 at 20:16, Heikki Linnakangas
> <heikki.linnakangas@iki.fi>  wrote:
>> If recovery_target_timeline is set to 'latest' and standby mode is enabled,
>> periodically rescan the archive for new timelines, while waiting for new WAL
>> segments to arrive. This allows you to set up a standby server that follows
>> the TLI change if another standby server is promoted to master. Before this,
>> you had to restart the standby server to make it notice the new timeline.
>
> Can we make recovery_target_timeline='latest' the default when we are
> in standby mode?  That would suddenly make it a lot easier to "repoint> a slave" after a switchover...

Hmm, seems reasonable. 'latest' is what you usually want, at least in 
standby mode. Though it would be strange to have a different default 
depending on the value of another setting. Maybe we should change the 
default regardless of standby_mode?

Wë́'d need a magic value to mean the current default behavior, to recover 
to the current timeline. 'current'?

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com

On Mon, Mar 7, 2011 at 20:24, Heikki Linnakangas
<heikki.linnakangas@enterprisedb.com> wrote:
> On 07.03.2011 21:20, Magnus Hagander wrote:
>>
>> On Mon, Mar 7, 2011 at 20:16, Heikki Linnakangas
>> <heikki.linnakangas@iki.fi>  wrote:
>>>
>>> If recovery_target_timeline is set to 'latest' and standby mode is
>>> enabled,
>>> periodically rescan the archive for new timelines, while waiting for new
>>> WAL
>>> segments to arrive. This allows you to set up a standby server that
>>> follows
>>> the TLI change if another standby server is promoted to master. Before
>>> this,
>>> you had to restart the standby server to make it notice the new timeline.
>>
>> Can we make recovery_target_timeline='latest' the default when we are
>> in standby mode?  That would suddenly make it a lot easier to "repoint
>
>> a slave" after a switchover...
>
> Hmm, seems reasonable. 'latest' is what you usually want, at least in
> standby mode. Though it would be strange to have a different default
> depending on the value of another setting. Maybe we should change the
> default regardless of standby_mode?

Seems like a much narrower usecase in ordinary recovery mode, but we
could definitely change both..


> Wë́'d need a magic value to mean the current default behavior, to recover to
> the current timeline. 'current'?

I didn't realize we didn't already have that. In principle, i think we
should *always* be able to specify in a config file whatever comes out
as a default. There should be no magic behavior that cannot be
explicitly specified.

--
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/