Re: Re: [COMMITTERS] pgsql: Make standby server continuously retry restoring the next WAL

On Thu, Mar 25, 2010 at 8:23 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
> PANICing won't change the situation, so it just destroys server
> availability. If we had 1 master and 42 slaves then this behaviour would
> take down almost the whole server farm at once. Very uncool.
>
> You might have reason to prevent the server starting up at that point,
> when in standby mode, but that is not a reason to PANIC. We don't really
> want all of the standbys thinking they can be the master all at once
> either. Better to throw a serious ERROR and have the server still up and
> available for reads.

OK. How about making the startup process emit WARNING, stop WAL replay and
wait for the presence of trigger file, when an invalid record is found?
Which keeps the server up for readonly queries. And if the trigger file is
found, I think that the startup process should emit a FATAL, i.e., the
server should exit immediately, to prevent the server from becoming the
primary in a half-finished state. Also to allow such a halfway failover,
we should provide fast failover mode as pg_standby does?

Regards,

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