Re: Synchronous replication - patch status inquiry

On 02/09/10 17:06, Simon Riggs wrote:
> On Thu, 2010-09-02 at 08:59 -0400, Robert Haas wrote:
>> On Thu, Sep 2, 2010 at 8:44 AM, Simon Riggs<simon@2ndquadrant.com>  wrote:
>>> "All standbys" has no meaning without registration. It is not a question
>>> that needs an answer.
>>
>> Tell that to the DBA.  I bet s/he knows what "all standbys" means.
>> The fact that the system doesn't know something doesn't make it
>> unimportant.
>
>> I agree that we don't absolutely need standby registration for some
>> really basic version of synchronous replication.  But I think we'd be
>> better off biting the bullet and adding it.  I think that without it
>> we're going to resort to a series of increasingly grotty and
>> user-unfriendly hacks to make this work.
>
> I'm personally quite happy to have server registration.
>
> My interest is in ensuring we have master-controlled robustness, which
> is so far being ignored because "we need simple". Refrring to above, we
> are clearly quite willing to go beyond the most basic implementation, so
> there's no further argument to exclude it for that reason.
>
> The implementation of master-controlled robustness is no more difficult
> than the alternative.

I understand what you're after, the idea of being able to set 
synchronization level on a per-transaction basis is cool. But I haven't 
seen a satisfactory design for it. I don't understand how it would work 
in practice. Even though it's cool, having different kinds of standbys 
connected is a more common scenario, and the design needs to accommodate 
that too. I'm all ears if you can sketch a design that can do that.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com