Re: Standby registration

On Thu, Sep 23, 2010 at 6:49 PM, Dimitri Fontaine
<dfontaine(at)hi-media(dot)com> wrote:
> Automatic registration is a good answer to both your points A)
> monitoring and C) wal_keep_segments, but needs some more thinking wrt
> security and authentication.

Aside from standby registration itself, I have another thought for C). Keeping
many WAL files in pg_xlog of the master is not good design in the first place.
I cannot believe that pg_xlog in most systems has enough capacity to store many
WAL files for the standby.

Usually the place where many WAL files can be stored is the archive. So I've
been thinking to make walsender send the archived WAL file to the standby.
That is, when the WAL file required for the standby is not found in pg_xlog,
walsender restores it from the archive by executing restore_command that users
specified. Then walsender read the WAL file and send it.

Currently, if pg_xlog is not enough large in your system, you have to struggle
with the setup of warm-standby environment on streaming replication, to prevent
the WAL files still required for the standby from being deleted before shipping.
Many people would be disappointed about that fact.

The archived-log-shipping approach cuts out the need of setup of warm-standby
and wal_keep_segments. So that would make streaming replication easier to use.
Thought?

Regards,

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