アルハイト wrote:
> Hi,
>
> I have recently had to install Slony at work. Everything works fine 
> however, I do have a single question regarding Slony's configuration. 
> Is it at all possible to throttle the speed at which slony performs an 
> update? (not $SYNC_CHECK_INTERVAL) I am asking because my boss would 
> like to lower the cpu usage on slave nodes during an update. If there 
> are any other good ways of lowering cpu usage during updates, I would 
> be happy to hear them!
>
> Thank you in advance,
> Berthold
>
I don't see much of a way to do this, short of actually suppressing 
replication.

The main work that is done is the INSERT/UPDATE/DELETE stream, and I'd 
think that the only effects you can reasonably have on that would be to, 
in some fashion, throttle Slony-I *part* of the time, which would mean 
that you'd push the work to a different point in time.

If you defer the work, that will tend to mean that there will be a 
larger set of updates, which would mean that CPU load would be elevated 
somewhat less often, but for longer periods of time.

Two scenarios might be (I'm making up numbers out of the air!)

 - Suppose you let Slony-I apply changes continually, then it might use 
40% of the CPU all the time

 - If you (by some means, I'm not quite certain what!) defer the work, 
then there would be periods of time when it uses 0% CPU, because no work 
is being done, but, since that work needs to be done, about 40% of the 
time, it would increase CPU usage to ~100%.

I suppose it might be an interesting idea to try to get the slon to look 
at the system load, and process fewer SYNCs if the number is high.  
That's definitely a "surgery-ish" change.