Hi,
On Fri, Jun 5, 2009 at 9:24 PM, Kolb, Harald (NSN -
DE/Munich)<harald.kolb@nsn.com> wrote:
>> Good point. I also think that this makes a handling of failover
>> more complicated. In other words, clusterware cannot determine
>> whether to do failover when it detects the death of the primary
>> postgres. A wrong decision might cause split brain syndrome.
> Mh, I cannot follow your reflections. Could you explain a little bit
> more ?
>>
>> How about new GUC parameter to determine whether to restart
>> postmaster automatically when it fails abnormally? This would
>> be useful for various failover system.
The primary postgres might restart automatically after clusterware finished
failover (i.e. the standby postgres has came up live). In this case, postgres
would work in each server, and they are independent of each other. This
is known as one of Split-Brain syndrome. The problem is that, for example,
if they share the archival storage, some archived files might get lost; the
original primary postgres might overwrite the archived file which is written
by the new primary.
On the other hand, the primary postgres might *not* restart automatically.
So, it's difficult for clusterware to choose whether to do failover when it
detects the deatch of the primary postgres, I think.
> A new GUC parameter would be the optimal solution.
> Since I'm new to the community, what's the "usual" way to make this
> happen ?
The followings might be a good reference to you.
http://www.pgcon.org/2009/schedule/events/178.en.html
http://wiki.postgresql.org/wiki/Submitting_a_Patch
Regards,
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center