[Bucardo-general] One node down scenario

Greg Sabino Mullane greg at endpoint.com
Fri Feb 8 15:40:59 UTC 2013

> Question is:
> * what is best solution to handle multi-master replication but in
> non-blocking way

Well, that is tricky. For multimaster replication, you really need all 
the sources to be available at once. If a row is updated, Bucardo needs 
to see which source should "win" for that row and become the authoritative 
row which gets copied everywhere else. If only two of three sources are 
available, it can't do that. It's possible Bucardo could be rearchitected 
to handle things differently, but allowing A <=> B to continue if C is 
down, and then when C is back up, do the full A <=> B <=> C (by keeping 
all records of changed rows around). But there are a lot of issues and 
corner cases with doing it that way.

Right not, the best solution is probably two sync, A<=>B and B<=>C, 
with B being marked as makedelta.

> * is there a way for the sync to populate all deltas since a
> specific txntime to a specific target?

You cannot outright, but if the rows are there from another sync, 
Bucardo should automatically use those, as the deltas are not tagged 
as belonging to a specific sync. But they get removed by the VAC daemon
very quickly after a sync runs, so the window for piggybacking 
onto an existing syncs deltas will be small if the original sync is 

Greg Sabino Mullane greg at endpoint.com
End Point Corporation
PGP Key: 0x14964AC8
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