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Java Forum / Databases / May 2004

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universal JDBC replicating proxy

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henk53 - 14 May 2004 13:42 GMT
I would like to have a constantly updated copy of my DB. In order to
realize this I have though of the following scheme:

A server is equiped with 3 NICs and is running a special 'proxy' JDBC
implementation.
The only thing this JDBC proxy does is:

1) Forwarding every update request on both ports. On each port a
server is running a JDBC compliant DB (in my case, postgresql)

2) Forwarding every select request on only 1 port.

Theoretically, this would give me a total synchronized DB, wouldn't
it? However, this sounds relative simple to implement. I've seen a
couple of replication efforts undertaken for postgresql that seems to
take forever to finish. For the record, the second database does not
have to do anything. The only thing I need is a copy of the complete
DB which is current up to the last transaction.

Am I overlooking something?
Mladen Adamovic - 14 May 2004 14:43 GMT
> Am I overlooking something?

man rsync
?

Signature

Mladen Adamovic
Department of Computer Enigneering
Faculty of Electrical Engineering
University Of Banja Luka

henk53 - 15 May 2004 22:47 GMT
> > Am I overlooking something?
> man rsync
> ?

Nope, didn't overlook that. In fact rsync is one of the first things I
looked at.

I quote from the High availability postgres project:
(http://www.taygeta.com/ha-postgresql.xml)

----------------------
use rsync.  This method will keep the volume of data being moved
between the servers down.  The problem is that since this method works
with the data files, its not supposed to work.  I have found that in
practice, for large databases with low transaction volumes, that it
can work.  If you have large databases with a low INSERT/UPDATE rates,
you might want to experiment with this approach to see if it works for
you.
-----------------------

I have a high transaction DB, so this is certainly not going to work,
but thanks for you kind reply anyway :)
Roedy Green - 16 May 2004 01:38 GMT
>I would like to have a constantly updated copy of my DB. In order to
>realize this I have though of the following scheme:

IF you have simply a list of files to replicate to a number of
clients, you can use the Replicator.  Its advantage is it uses only
http so it requires nothing special for firewalls.

It just changes what has changed, and avoids changing what has been
redated, but has not really changed.

See http://mindprod.com/products.html#REPLICATOR.

Oracle has some stuff for keeping SQL databases in sync that does not
require you to write custom code. Oracle stuff though is pricey.

Signature

Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.



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