On Wed, Sep 10, 2008 at 12:26 AM, Heikki Linnakangas
<heikki.linnakangas@enterprisedb.com> wrote:
> If a slave falls behind, how does it catch up? I guess you're saying that it
> can't fall behind, because the master will block before that happens. Also
> in asynchronous replication? And what about when the slave is first set up,
> and needs to catch up with the master?
The mechanism for the slave to catch up with the master should be
provided on the outside of postgres. I think that postgres should provide
only WAL streaming, i.e. the master always sends *current* WAL data
to the slave.
Of course, the master has to send also the current WAL *file* in the
initial sending just after the slave starts and connects with it.
Because, at the time, current WAL position might be in the middle of
WAL file. Even if the master sends only current WAL data, the slave
which don't have the corresponding WAL file can not handle it.
regards
--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center