Re: Synchronous replication: Promotion of Standby to Primary

Hi,

On Mon, May 4, 2009 at 11:07 PM, K, Niranjan (NSN - IN/Bangalore)
<niranjan(dot)k(at)nsn(dot)com> wrote:
> Hi,
>
> Re-opening the discussion related to triggers to promote standby server.
> In the earlier dicussion, there were 2 proposals, Trigger based on file
> and trigger based on signals. I think there was no conclusion on this.
> http://archives.postgresql.org/pgsql-hackers/2008-12/msg01231.php
>
> According to the proposal, it seems to be better if signals are used as
> we can avoid checking the file existance in the loop. Or the other
> approach is to use inotify (http://en.wikipedia.org/wiki/Inotify). But
> portability to other unix like OS is an issue to look for.
>
> Could you please get back which is being implemented/ considered for
> promotion of standby?

I had to choose the trigger file approach last time since the patch
was also using warm-standby in part. But, in 8.5, synch-rep is
going to work without warm-standby. So, we can choose also the
trigger based on signals. In this case,

Since using kill(1) command directly for the trigger signal is troublesome,
we should also provide the wrapper command such as "pg_ctl trigger/promote".

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center