Re: refusing connections based on load ... - Mailing list pgsql-hackers

The Hermit Hacker wrote:
> Agreed ... by default, the loadavg method could be set to zero, to ignore
> ... I don't care if I'm off by 1min before I catch the increase, the fact
> is that I have caught it, and prevent any new ones coming in until it
> drops off again ...
>
> Make it two variables:
>
> transla
> rejectla
>
> if transla is hit, restrict on transactions, letting others connect, but
> putting them on hold while the la drops again ... if it goes above
> rejectla, refuse new connections altogether ...
>
> so now I can set something like:
>
> transla = 8
> rejectla = 16
>
> but if loadavg goes above 16, I want to get rid of what is causing the
> load to rise *before* adding new variables to the mix that will cause it
> to rise higher ...
>
> and your arg about permissions (Tom's, not Peter's) is moot in at least 3
> of the major systems (Linux, *BSD and Solaris) as there is a getloadavg()
> function in all three for doing this ...
   I've  just  recompiled  my php4 module to get sysvsem support   and limited the number of concurrent DB transactions
on  the   application    level.    The   (not   yet   finished)   TPC-C   implementation I'm working on scales about
3-4 times  better   now. That's an improvement!
 
   This  proves that limiting the number of concurrently running   transactions is sufficient to  keep  the  system
load down.   Combined these two look as follows:
 
   -   We start with a fairly high setting in the semaphore.
   -   When the system load exceeds the high-watermark, we don't       increment the semaphore back after transaction
end (need       to ensure that at least a small minimum of xacts is left,       but that's easy).
 
   -   When the system goes back to normal load level, we slowly       increase the semaphore again.
   This  way  we might have some peek pushing the system against   the wall for a moment. If that doesn't go  away
quickly, we   just delay users (who see some delay anyway actually).
 


Jan

--

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