[pgpool-hackers: 3165] New feature proposal: On demand scale up and scale down of child processes

[Muhammad Usama]

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.

Thanks
Best Regards
Muhammad Usama
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