Re: Streaming replication status

On Tue, Jan 12, 2010 at 08:22, Heikki Linnakangas
<heikki.linnakangas@enterprisedb.com> wrote:
> Greg Smith wrote:
>> I don't think anybody can deploy this feature without at least some very
>> basic monitoring here.  I like the basic proposal you made back in
>> September for adding a pg_standbys_xlog_location to replace what you
>> have to get from ps right now:
>> http://archives.postgresql.org/pgsql-hackers/2009-09/msg00889.php
>>
>> That's basic, but enough that people could get by for a V1.
>
> It would be more straightforward to have a function in the standby to
> return the current replay location. It feels more logical to poll the
> standby to get the status of the standby, instead of indirectly from the
> master. Besides, the master won't know how far the standby is if the
> connection to the standby is broken.
>
> Maybe we should just change the existing pg_current_xlog_location()
> function to return that when recovery is in progress. It currently
> throws an error during hot standby.
>

Not sure. I don't really like to monitor functions that return
different things depending on a scenario.

Assume I monitor it, and then do a failover. Suddenly the values I
monitor mean something else.

I think I'd prefer a separate function to monitor this status on the
slave. Oh, and it'd be nice if that one worked in HS mode both when in
streaming and non-streaming mode :-)


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