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Re: Synchronous replication - patch status inquiry

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, David Fetter <david(at)fetter(dot)org>, Bruce Momjian <bruce(at)momjian(dot)us>, fazool mein <fazoolmein(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Synchronous replication - patch status inquiry
Date: 2010-09-02 14:32:33
Message-ID: 4C7FB581.40802@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackers
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(at)2ndquadrant(dot)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

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