Re: AW: Postgres Replication

Hello

I have hacked up a replication layer for Perl code accessing a
database throught the DBI interface. It works pretty well with MySQL
(I can run pre-bender slashcode replicated, haven't tried the more
recent releases).

Potentially this hack should also work with Pg but I haven't tried
yet. If someone would like to test it out with a complex Pg app and
let me know how it went that would be cool.

The replication layer is based on Eric Newton's Recall replication
library (www.fault-tolerant.org/recall) and requires that all
database accesses be through the DBI interface.

The replicas are live, in that every operation affects all the
replicas in real time. Replica outages are invisible to the user, so
long as a majority of the replicas are functioning. Disconnected
replicas can be used for read-only access.

The only code modification that should be required to use the
replication layer is to change the DSN in connect():

my $replicas = '192.168.1.1:7000,192.168.1.2:7000,192.168.1.3:7000';
my $dbh = DBI->connect("DBI:Recall:database=$replicas");

You should be able to install the replication modules with:

perl -MCPAN -eshell
cpan> install Replication::Recall::DBServer

and then install DBD::Recall (which doesn't seem to be accessible from
the CPAN shell yet, for some reason), by:

wget http://www.cpan.org/authors/id/AGUL/DBD-Recall-1.10.tar.gz
tar xzvf DBD-Recall-1.10.tar.gz
cd DBD-Recall-1.10
perl Makefile.PL
make install

I would be very interested in hearing about your experiences with
this...

Thanks

#!