Re: FCGI process handling and fine-tunning for saving CPU, under Perl code

> > Here´s the problem: I´ve finally made FCGI (and also
> > CGI::Fast, but not mod_perl, as my host doesn´t support
> > it) work at my shared account. But just can´t figure out
> > how to handle it, I mean, how do I restart the processes
> > when I update the script code? How do I know the number of
> > the process??
>
> Two options: you can have the mod_fastcgi process manager
> (if you use that) notice when your script file is updated
> on disk and then automatically restart it when it is
> (assuming you can switch that option on); this is limited
> by the fact that it only checks your main script file, so
> if you have modules which you also change, this won't help
> you.

I am not aware I have a mod_cgi process manager installed, but in fact, this
correlate updates happen just all the time. So I really will need to
kill/restart through the shell.

Alternatively, you can check the timestamp on your
> script files in your main loop. We have code to do this
> here:
>
https://secure.mysociety.org/cvstrac/getfile/mysociety/perllib/mySociety/Wat
chUpdate.pm
> though it's a little ugly.

I have tried to use it, but for some reason it didn´t work, I mean, the
script stopped working after including the code calling the module. Also, I
fear that this verification will consume precious CPU, maybe it´s better to
restart/kill the processes myself, as soon as I know how to do that.

> > My main goal with FCGI is to save precious CPU minutes,
> > as the traffic is increasing a lot (and my host will kick
> > me out if I get too heavy-processing, as they just dont
> > have dedicated servers available). You guys know if the
> > CPU savings are worth adapting the code? I mean, can I
> > expect to use, like, 30% less CPU?
>
> That depends on the startup cost of your program vs the
> marginal cost of serving one request, basically. Without
> knowing any more detail it's impossible to comment; really
> you need to measure it now and decide whether it's
> worthwhile.

All scripts load 5 method libraries with more than 10 thousand lines total,
and connect to mysql before doing anything. So FCGI it may be a good thing
to save CPU, right? You´d say I can save 50% CPU?

> > And, last but not least, I am not quite sure about
> > converting guidelines, like avoiding referencing $q (new
> > CGI) inside subs and all. If you can offer me some links
> > for that, it would be great too.
>
> Again, without seeing your code, it's impossible to
> comment, but the basic skeleton I'd recommend for a
> perl FastCGI server would be:

This one is fine now. I´ve succeeded adapting a production script, without
leaks. The concern is only how to tell the server to restart that creature
now that I´ve made updates! ...lghs I wait for your help on that.

Thanks a lot Chris!

phoenix_fly

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