[mysql-dde] Re: The mutual conflict problem

  • From: "Peter B. Volk" <PeterB.Volk@xxxxxxx>
  • To: <mysql-dde@xxxxxxxxxxxxx>
  • Date: Mon, 12 Dec 2005 18:25:48 +0100

ok..
----- Original Message ----- 
From: "Fabricio Mota" <fabricio.oliveira@xxxxxxxxxxxxxxxx>
To: <mysql-dde@xxxxxxxxxxxxx>
Sent: Monday, December 12, 2005 5:18 PM
Subject: [mysql-dde] Re: The mutual conflict problem


> Really, really... I must agree with you.
>
>
> But I still want to try suggesting another solution that does not depend
on
> a single master.
> I don't like no much this idea of a master.
>
> ----- Original Message ----- 
> From: "Peter B. Volk" <PeterB.Volk@xxxxxxx>
> To: <mysql-dde@xxxxxxxxxxxxx>
> Sent: Monday, December 12, 2005 1:01 PM
> Subject: [mysql-dde] Re: The mutual conflict problem
>
>
> > Ok I guess the list strips the images down:
> >
> > here are the links:
> >
> > www.inf.tu-dresden.de/~s7205538/dde/unique_management.jpg
> > www.inf.tu-dresden.de/~s7205538/dde/unique_management_sequenc.jpg
> >
> > Peter
> > ----- Original Message ----- 
> > From: "Peter B. Volk" <PeterB.Volk@xxxxxxx>
> > To: <mysql-dde@xxxxxxxxxxxxx>
> > Sent: Monday, December 12, 2005 3:56 PM
> > Subject: [mysql-dde] Re: The mutual conflict problem
> >
> >
> >> Hey,
> >> Well I could be solved by having GI-Key Masters. I've added 2 diagramms
> >> to
> >> show a few details.
> >>
> >> Peter
> >> ----- Original Message ----- 
> >> From: "Fabricio Mota" <fabricio.oliveira@xxxxxxxxxxxxxxxx>
> >> To: "dde" <mysql-dde@xxxxxxxxxxxxx>
> >> Sent: Monday, December 12, 2005 2:19 PM
> >> Subject: [mysql-dde] The mutual conflict problem
> >>
> >>
> >> > Hey Guy!
> >> > We have a problem with uniqueness management with any approach we
use.
> >> That is:
> >> >
> >> > Suppose Clients C1 and C2, connected respectivelly through servers S1
> > and
> >> S2.
> >> > Both clients try to insert a value k, into a unique-indexed column.
> >> Suppose they try to insert the value approximately during the same
time.
> >> >
> >> > If we think about to validate global uniqueness among servers before
to
> >> insert, then:
> >> >
> >> > 1 - C1 tries to insert it through S1 / at same time, C2 tries it
> >> > through
> >> S2.
> >> > 2 - S1 validates k / C1 locally. Uniqueness is ok. S2 validates k /
C2
> >> locally, too. Both are ok.
> >> > 3 - S1 request S2 about uniqueness of k. At aproximately the same
time,
> > S2
> >> request the same for S1.
> >> > 4a - if we consider a fully isolated transaction approach, then S1
will
> >> perform C1 command, and S2 will perform C2 command, too. That's an
> >> inconsistence!
> >> > 4b - if we consider the value k is shared during transactions, both
> >> servers will abort, because k is already there during remote
validation,
> >> causing a mutual abort.
> >> >
> >> > If we think about to validate global uniqueness among servers after
to
> >> insert, replicating global indexes, then:
> >> >
> >> > 1 - C1 tries to insert it through S1 / at same time, C2 tries it
> >> > through
> >> S2.
> >> > 2 - S1 validates k / C1 locally. Uniqueness is ok. S2 validates k /
C2
> >> locally, too. Both are ok.
> >> > 3 - S1 tries to sync S2 about its new value k. At aproximately the
same
> >> time, S2 tries to sync S1, too.
> >> > 4a - if we consider a fully isolated transaction approach, then S1
will
> >> update S2 with its k, and S2 will update S1 with its own k, too. That's
> >> an
> >> inconsistence, again.
> >> > 4b - if we consider the value k is shared during transactions, both
> >> servers will abort, because k is already there during remote
validation,
> >> causing a mutual abort.
> >> >
> >> > If we consider the hypothesis 4b, what criterion could be used for
both
> >> server to agree in which transaction to abort?
> >> >
> >> > Or so, what could we do in respect to it?
> >> >
> >> > Fabricio Mota
> >> > Analista de Sistemas
> >> > FCPC - Divisão de Planejamento do Cadastro Comercial
> >> > MySql-DDE discussion list
> >> > www.freelists.org/
> >> >
> >>
> >>
> >>
> >>
> >> MySql-DDE discussion list
> >> www.freelists.org/
> >>
> >
> > MySql-DDE discussion list
> > www.freelists.org/
> >
> >
>
> MySql-DDE discussion list
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