Re: Synchronous replication - patch status inquiry

Robert Haas wrote:
> On Tue, Sep 7, 2010 at 11:59 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
> >> What I *think* you're saying is that the slave doesn't send per-commit
> >> messages, but instead processes the WAL as it's received and then sends
> >> a heres-where-I-am status message back upstream immediately before going
> >> to sleep waiting for the next chunk. ?That's fine as far as the protocol
> >> goes, but I'm not convinced that it really does all that much in terms
> >> of improving performance. ?You still have the problem that the master
> >> has to fsync its WAL before it can send it to the slave. ?Also, the
> >> slave won't know whether it ought to fsync its own WAL before replying.
> >
> > Yes, apart from last sentence. Please wait for the code.
> 
> So, we're going around and around in circles here because you're
> repeatedly refusing to explain how the slave will know WHEN to send
> acknowledgments back to the master without knowing which sync rep
> level is in use.  It seems to be perfectly evident to everyone else
> here that there are only two ways for this to work: either the value
> is configured on the standby, or there's a registration system on the
> master and the master tells the standby its wishes.  Instead of asking
> the entire community to wait for an unspecified period of time for you
> to write code that will handle this in an unspecified way, how about
> answering the question?  We've wasted far too much time arguing about
> this already.

Ideally I would like the sync method to be set on each slave, and have
some method for the master to query the sync mode of all the slaves, e.g.
appname.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +