Re: Synchronous Log Shipping Replication

On Wed, 2008-09-10 at 10:06 +0200, Markus Wanner wrote:
> Hi,
>
> Simon Riggs wrote:
> > 1. Standby contacts primary and says it would like to catch up, but is
> > currently at point X (which is a point at, or after the first consistent
> > stopping point in WAL after standby has performed its own crash
> > recovery, if any was required).
> > 2. primary initiates data transfer of old data to standby, starting at
> > point X
> > 3. standby tells primary where it has got to periodically
> > 4. at some point primary decides primary and standby are close enough
> > that it can now begin streaming "current WAL" (which is always the WAL
> > up to wal_buffers behind the the current WAL insertion point).
>
> Hm.. wouldn't it be simpler, to start streaming right away and "cache"
> that on the standby until it can be applied? I.e. a protocol like:

Good idea!

This makes everything simpler, as user has to do only 4 things

1. start slave in "receive WAL, dont apply" mode
2. start walshipping on master
3. copy files from master to slave.
4. restart slave in "receive WAL" mode

all else will happen automatically.

---------------
Hannu