[pgpool-hackers: 3167] Re: New feature proposal: On demand scale up and scale down of child processes

Tatsuo Ishii ishii at sraoss.co.jp
Thu Dec 6 09:40:19 JST 2018

> Hi
> Currently Pgpool-II spawns the num_init_children number of child processes
> at the time of startup. This is the standard approach we follow in
> Pgpool-II since its inception. But this approach is not very optimal for
> the setups with variable load requirements. For example for the setups
> where we get instantaneous load spikes let say only for small amount of
> time, we still have to set the num_init_children in Pgpool-II to the
> maximum value, and most of the time the majority of the the child processes
> would be sitting idle and consuming the system resources.
> Like consider a case of some sports website which gets huge number of user
> when some sport event is happening, but for rest of the time it gets very
> few visitors. But with the current available options when designing the
> system using the Pgpool-II we have to set the num_init_children to the
> value what we expect to get at the maximum peak time and that number of
> children will be spawned by Pgpool-II at startup, which is a waste of
> resources.
> So my proposal is that instead of spawning all the num_init_children number
> of child process at startup, we scale up and scale down the number of child
> processes as per the demand. And only keep may be 10 percent of extra idle
> child processes at any time.
> I believe this approach will improve the load management and performance of
> Pgpool-II
> What are your thought and suggestions on this.

Do you have a performance measurement on this?

Best regards,
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php

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