Re: Sync Rep v17

Simon Riggs wrote:
> On Fri, 2011-02-18 at 21:39 -0500, Bruce Momjian wrote:
> > Simon Riggs wrote:
> > > Most parameters are set on the primary. Set
> > > 
> > >   primary: synchronous_standby_names = 'node1, node2, node3'
> > > 
> > > which means that whichever of those standbys connect first will
> > > become the main synchronous standby. Servers arriving later will
> > > be potential standbys (standby standbys doesn't sound right...).
> > > synchronous_standby_names can change at reload.
> > > 
> > > Currently, the standby_name is the application_name parameter
> > > set in the primary_conninfo.
> > > 
> > > When we set this for a client, or in postgresql.conf
> > > 
> > >   primary: synchronous_replication = on
> > > 
> > > then we will wait at commit until the synchronous standby has
> > > reached the WAL location of our commit point.
> > > 
> > > If the current synchronous standby dies then one of the other standbys
> > > will take over. (I think it would be a great idea to make the
> > > list a priority order, but I haven't had time to code that).
> > > 
> > > If none of the standbys are available, then we don't wait at all
> > > if allow_standalone_primary is set.
> > > allow_standalone_primary can change at reload.
> > 
> > Are we going to allow a command to be run when these things happen, like
> > archive_command does, or is that something for 9.2?
> 
> Not really sure which events you're speaking of, sorry. As I write, I
> don't see a place or a reason to run a command, but that might change
> with a longer explanation of what you're thinking. I wouldn't rule out
> adding something like that in this release, but I'm not around for the
> next week to add it.

Sorry.  I was thinking of allowing a command to alert an administrator
when we switch standby machines, or if we can't do synchronous standby
any longer.  I assume we put a message in the logs, and the admin could
have a script that monitors that, but I thought a pager-like command
would be helpful, though I don't think we do that in any other case, so
maybe it is overkill.  These are all optional ideas.

Also, I like that you are using application name here.

--  Bruce Momjian          http://momjian.us EnterpriseDB                             http://enterprisedb.com
 + It's impossible for everything to be true. +