Please allow me to wad into this discussion giving it a different view.
LDAP is a form of a database, it has Multi-Master afaik it runs somewhat
decently for two masters, can't we use a similar setup as say Fedora
Directory Server or OpenLDAP's replication strategy and with some modification/improvement use
it to help PostgreSQL do Multi-Master/Replication ?
Am I missing the point ?
Cheers,
Aly.
On Fri, 14 Oct 2005, Scott Marlowe wrote:
>On Thu, 2005-10-13 at 17:48, Tatsuo Ishii wrote:
>> > On Thu, Oct 13, 2005 at 10:53:51AM -0700, Chris Travers wrote:
>> > > Now, what about PgPool as a multimaster sync replication solution? Sure
>> > > it is statement level.... But is there any reason why you cannot have
>> > > multiple PgPool instances running against a number of DB servers?
>> >
>> > Well, to begin with, you have a serious race condition:
>> >
>> > pgpool begins T1 on M1 and M2.
>> > Someone logs into M2 and does some work in T2.
>> > M1 completes the work of T1.
>> > M2 completes the work of T2.
>> > pgpool issues COMMIT.
>> > M1 replies with the COMMIT.
>> > M2 detects a deadlock when T2 tries to COMMIT.
>> >
>> > Now what? There's nothing to prevent this in the system, as near as
>> > I can see, so it's just not bullet proof enough for the cases where
>> > people really, really need only five minutes of down time a year. If
>> > you _really_ needed that, you'd be willing (and able) to pay the
>> > costs. Of course, we can do what we can to make those costs go down.
>> > :-> But they're not that low yet.
>>
>> Why pgpool should bother? pgpool supposes every transaction should go
>> through pgpool. Your example sounds like someone logs into M2 and tries
>> to shut down it.
>
>I had the same thought. Every time I've set up a system with pgpool,
>I've always configured the db servers on an odd port, cut it off with a
>firewall to anything but the pgpool machine and set it to only answer to
>pgpool's IP and only let users access the system through pgpool.
>
>USers accessing machines behind the scenes is a VERY bad idea. It's not
>a pgpool bug, is a user bug. :)
>
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>TIP 2: Don't 'kill -9' the postmaster
>
--
Aly S.P Dharshi
aly.dharshi@telus.net
"A good speech is like a good dress
that's short enough to be interesting
and long enough to cover the subject"
