[Bucardo-general] Questions on `add sync` params

Greg Sabino Mullane greg at endpoint.com
Thu Oct 18 02:30:09 UTC 2012


> I could find nothing done with the `limitdbs` parameter 
> other than storage. Is it a no-op? Placeholder for future functionality?

Most of these are leftover from Bucardo4, and either are no longer needed, 
awaiting a full port, or can just be removed. The limitdbs should probably 
stay: it is there to prevent syncs from overwhelming a server. In other 
words, if set to 3, no more than 3 Bucardo syncs will target that server 
at one time (the rest will wait until a slot is free). Verdict: placeholder.

> The `do_listen` parameter seems to be used in only a few 
> places as an alias for the `ping` param. True?

Yes: I cannot see a difference. Nuke it.

> I could not determine what the `checktime` parameter was used for. So…what *is* it for?

It's the maximum time a sync should go before being kicked. Useful for busy 
systems where you don't want the overhead of notify triggers. Similar 
to checkpoint_timeout.

> What is the `makedelta` stuff? Do users need to care about it, or 
> use `source_makedelta` or `target_makedelta`?

It's important, but not clear yet if we want a single makedelta or 
want to keep the source vs target split. It's needed in case more 
than one sync is replicating the same table. As Bucardo disables 
triggers, the bucardo delta tables are not fired when Bucardo itself 
is making a change (hello infinite loops!). If makedelta is on, 
Bucardo will create entries in the delta tables "manually". I don't 
think this works for Bucardo5 yet. But need for it should be rare.

> It looks as if `priority` is used for ordering in the output of `list` 
> and a few other places, but I couldn't see it used anywhere to 
> prioritize syncs. Have I missed it? What's this parameter for?

Placeholder. In theory, more than one sync could be competing for access 
to a server (e.g. the limitdbs above). In which case, it can be nice to 
have a way to state that one sync is more important than another.

> The `overdue` and `expired` params appear to be no-ops. True?

No - they are used by bucardo_report and especially for Nagios tie-ins.

> What is the `track_rates` parameter for? I see some stuff about 
> tracking rates, but don't understand what might be tracked or why.

It's tracking how long a sync run takes. I'm not sure how useful it 
still is. If it's a lot of trouble to get working right in bucardo5, 
I say we take a quick poll to see if anyone is using it and nuke it.

> It looks as if `customselect` (and `usecustomselect`) boolean is 
> deprecated in favor of `customcols` objects, which is fine. But if 
> folks still want to use it, where does one specify the custom select 
> statement to actually use?

$ bucardo add customcols mytable "SELECT id, foo, bar"

See t/20-postgres.t


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