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