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. :) > >---------------------------(end of broadcast)--------------------------- >TIP 2: Don't 'kill -9' the postmaster > -- Aly S.P Dharshi aly.dharshi@xxxxxxxxx "A good speech is like a good dress that's short enough to be interesting and long enough to cover the subject" ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
