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

[David E. Wheeler]

On Oct 17, 2012, at 7:30 PM, Greg Sabino Mullane <greg at endpoint.com> wrote:

>> 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.

So, it does not actually do anything now? Should I create an issue for it?

You've noticed all the issues I've created, I assume. :-)

  http://github.com/bucardo/bucardo/issues

>> 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.

Did it used to do something different? Should I make it an alias for ping?

>> 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.

Okay.

>> 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.

Well, since 5.0 is so close to done, perhaps we shouldn't worry about getting rid of the source vs. target split just now, yes? In which case, does the makedelta stuff need to be hooked back up?

>> 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.

Okay, I will document it as currently just being for display purposes.

>> The `overdue` and `expired` params appear to be no-ops. True?
> 
> No - they are used by bucardo_report and especially for Nagios tie-ins.

Okay? What for? What do they mean?

>> 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.

Is Bucardo currently logging that information somewhere?

>> 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"

Yeah, but the code for customselect says to use customcols instead. customcols seems to implicitly turn on customselect, no?

David


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