Message-ID: <000e01c313f8$941ef5e0$10d4a8c0@mm.eutelsat.org>
From: "Mendola Gaetano" <mendola@bigfoot.com>
To: "Diehl, Jeffrey" <jdiehl@sandia.gov>,
	"'Michael A Nachbaur'" <mike@nachbaur.com>, <pgsql-sql@postgresql.org>
References: <B51F0C636E578A4E832D3958690CD73E0130C42C@es04snlnt.sandia.gov>
Subject: Re: pgsql Replication Proxy (was Re: Replication for a
Date: Tue, 6 May 2003 19:54:41 +0200
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Postgres don't have the support ( yet ) for the 2 phase commit, so
I think that is impossible do it now.
What happen if the last server do an error in commit phase ?

Regards
Gaetano

----- Original Message ----- 
From: "Diehl, Jeffrey" <jdiehl@sandia.gov>
To: "'Michael A Nachbaur'" <mike@nachbaur.com>; <pgsql-sql@postgresql.org>
Sent: Tuesday, May 06, 2003 6:28 PM
Subject: Re: pgsql Replication Proxy (was Re: [SQL] Replication for a


> I love this idea.  The proxy could return immediately instead of making my
> program block on update.
>
> One note, though.  Instead of a stack, you need a FIFO.  For example:
>
> delete from sometable where field=value;
> insert into sometable (field) values (value1);
> insert into sometable (field) values (value2);
> ....
>
>
> This code breaks in a stack and only works in a fifo.  Minor point,
though.
>
> So do we have a volunteer to write such a tool?  <grin>
>
> Mike Diehl.
>
> -----Original Message-----
> From: Michael A Nachbaur [mailto:mike@nachbaur.com]
> Sent: Monday, May 05, 2003 1:57 PM
> To: pgsql-sql@postgresql.org
> Subject: pgsql Replication Proxy (was Re: [SQL] Replication for a large
> database)
>
>
> I've thought some more about this, and I want to pass this idea past you
> guys.
> What do you think about a replication proxy, essentially a daemon that
sits
> between a PostgreSQL client and server.  Every single SQL query,
transaction
>
> statement, etc that the proxy recieves it repeats back to all the database
> servers.  In this way, if a back-end database server goes down queries
will
> continue unabated (except the downed server won't recieve updates).
>
> Basically, the proxy server could intercept these queries and place them
in
> a
> stack (on a per-database basis) and when every server in the queue
> acknowledges the update, the query is removed from the stack.  Each
database
>
> server can have their own position in the stack, so if servers A and B
> successfully run a query, but C doesn't (e.g. it requires human
> intervention), C is removed from the list of acceptable servers but A and
B
> can keep moving through the queue.
>
> What do you think?  Also, should this discussion be moved to another
mailing
>
> list?
>
> On Monday 05 May 2003 12:26 pm, Michael A Nachbaur wrote:
> > I have thought about this.  The problem I come into is data consistancy.
> I
> > have at least 8 different processes that harvest data, and an intranet
> > website that can also manipulate the database (to assign customers to
> > different packages, re-assign modems to different customers, etc).
Trying
> > to maintain consistancy across the entire application would be such a
> > nightmare, I don't want to think about it.
> >
> > If I go with a centralized middleware server that manages all database
> > access, then I could perhaps do that in there...and then I could use
> > transactions on both databases, and if either transaction fails then
I'll
> > roll back the other.  But this would make my entire framework very
rigid.
>
>
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