http://www.slony.info/bugzilla/show_bug.cgi?id=174

--- Comment #6 from Christopher Browne <cbbrowne at ca.afilias.info> 2010-12-09 13:37:56 PST ---
(In reply to comment #5)
> (In reply to comment #2)
> > Proposed...  Add a table that will be replicated via event publishing that
> > captures tuples of the form [excluder, excludee]
> > 
> > That is, node [excluder] will ignore events coming from node [excludee].
> > 
> > (Open question: Will it just be SYNC events that are ignored?  Seems quite
> > likely apropos...)
> 
> How would WAIT FOR (todays manual WAIT FOR - ignoring any automatic one) work
> if you ignore non sync events?  

> Also, just because node 1 is excluding node 4 doesn't mean that node 3 is
> excluding node 4 (it probably isn't).  How will WAIT FOR change.

If it's only present in the new world (e.g. - where WAIT is implicit), then
that's not *totally* important :-).

But sure, it's a good question.

I imagine the result is that events from Node A will get ignored on Node B.

WAIT FOR presently has 2 forms:

a) WAIT FOR a particular node; this only breaks down if you ask to wait for an
event from Node A arriving at Node B.  I think we can make such a request error
out - it's not sensible to ask for this if there's an "exclusion" present.

b) WAIT FOR ALL.  I expect we'd have these requests ignore exclusions.

Seems sensible?

> Also what are the implications with respect to FAILOVER and MOVE SET or
> rehshaping a subscription for this change.

I expect we have to refuse these requests.  It shouldn't be problematic to add
tests similar to
<https://github.com/cbbrowne/slony1-engine/commit/796df78da7e8e639e7df2df642800671ca945b04>
to FAILOVER and MOVE SET.

> Also can you propose some syntax for making a node excluded?
> 
> What happens if you no longer want a node to be excluded?  Especially if the
> events have already been deleted on the excluder.

I'd think slonik syntax would look like:

IGNORE NODE (IGNORE ID=2, IGNORE BY=4);
UNIGNORE NODE( ID=2, IGNORE BY=4);

Whether events have been deleted or not seems beside the point; that's a
question at the time of SUBSCRIBE SET, MOVE SET, FAILOVER.

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