Just a clarification. When I say "Statistically, it is almost
impossible that the 20 nodes will be online simultaneously", I am
making a statement about my specific scenario, not about Internet
connection in a general node. Some nodes of my client are located in
ships, and these ships may be sailing all around the world. Obviously,
the Internet connection that a ship can have in the middle of the
Pacific ocean is null. That's why I say that the 20 nodes will "never"
be online simultaneously: statistically one of the ships will be
sailing somewhere with a poor or inexisting Internet connection.
Best regards,
José Montero
Bsc in Computer Engineering
Bsc Master in Computer Science
brain-tec AG
IT-Solutions
Überlandstrasse 10
CH-3900 Brig
www.brain-tec.ch <http://www.brain-tec.ch>
Am Sun 07 Apr 2013 01:10:41 PM CEST schrieb Michelle Sullivan:
José Montero wrote:
Hello everyone,
A client of my company needs a multi-master replication mechanism for
PostgreSQL and I have been suggested to use Bucardo. I know the stable
version of Bucardo doesn't allow multi-master replication, but the
beta version 5 does.
I have tested the way Bucardo 5 performs syncs and it looks nice.
However, I've encountered a major problem that, according to what I've
read in forums, may be an implementation decision:
*A sync is aborted if one of the involved DBs is offline. *
My client needs to replicate data among more than 20 nodes.
Statistically, it is almost impossible that the 20 nodes will be
online simultaneously. Therefore, I really need a sync to synchronize
"now" as many databases as possible and later, when the offline
databases come online, to synchronize them. Is there a way to achieve
what I need using the current version of Bucardo (4.99.7)?
Whilst I agree with your issue regarding a 'catch up' mode I do disagree
with your statement 'Statistically, it is almost impossible that the 20
nodes will be online simultaneously.' ... My nodes are online 99% of the
time, and whilst I don't have 20 I have 7 all around the world connected
via the Internet...
That said, I do support some sort of 'catch up mode' as a concept. I
do have issues with some of the remote nodes going offline from time to
time, and when they do (particularly due to routing issue of the
Internet) having replication stop is a major pain the rectum...
particularly if its due to a hardware failure that takes 24 hours to get
resolved. Replication should continue and the host when it comes up
should be placed into a 'read-only, catch up' mode whilst the catchup
sync is performed. All my remote nodes are slave only so it's not too
much of an issue that way for me, however I do have a cluster of 4
masters (2 east coast, 2 west cost) that should a master fail it should
be placed in read-only on startup whilst the DB is synced with
outstanding changes. Greg, would this be possible to look at?
Regards,
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