Re: Multimaster

On 2 April 2016 at 02:15, Moreno Andreo <moreno(dot)andreo(at)evolu-s(dot)it> wrote:

> Actually we have to improve what our replicator is doing: it's only
> replicating the single user's database. The improvement should that we can
> put it on the "server" (in some cases there are groups of users sharing a
> dedicated server) and, given a configuration of what and how to replicate,
> it should replicate more than one DB a time.
>

That's a layer on top as far as pglogical is concerned. It's only
interested in a single database at a time.

The same is true of BDR.

A tool that automatically configures newly found databases to be replicated
should be pretty trivial to write, though.

> We were beginning to "translate" (and then improve) this program in c#,
> when I bumped into articles pointing to BDR, and I started taking a look.
> But it seems that is good to replicahe whole servers, and still hasn't the
> granularity we need.

Huh?

BDR is configured database-by-database. The only exception is with
bdr_init_copy, for initial setup using binary base backups; in that case
all databases are copied.

It sounds like you actually *want* to replicate all databases at once.
Presumably the reason you're not just using physical streaming replication
for that is that different hosts have a different set of writeable
databases? E.g.

[Node A] [Node B]
[DB-1] -> [DB-1]
[DB-2] -> [DB-2]
[DB-3] <- [DB-3]
[DB-4] <- [DB-4]

so each DB is written from only one node at a time, but both nodes have
writeable DBs. Right?

--
Craig Ringer http://www.2ndQuadrant.com/
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