Schedule subroutines in perl - perl

Question

I'm parsing a log file, and I'm required to produce JSON file with results for every 1 second, 5, 5 min, 15, 30, 1 hour ..etc
I'm confused about the concept here, it is possible to write one big infinite while loop that include number of subroutines each will perform its parsing based on different time interval.
Here is I have so far, not sure if this is the right approach
#!/usr/bin/perl
use strict;
use warnings;
$ | = 1; # Ensure output appears
my $interval = 1;
my #command = "echo processing ...";
my $count = 0;
while (1) {
`since access.log | json_convert.pl
sleep $interval - time % $interval;
system #command;
}

Answer 1

Repeated sleep calls will drift rapidly because they don't take into account the time spent creating the JSON data. I would also be very wary of using system calls to do the data manipulation as it is bound to slow things down, and you may well overrun the one-second response time that you are looking for. Do it all within Perl instead
I recommend you look at the excellent EV module. The periodic event type is what you need
Here's a very short example. Your own callback subroutine should examine the time at which it is called to determine what to do, according to whether it is a multiple of 5 seconds, 60 seconds etc. Alternatively you could set up multiple event loops, one for each interval. The module makes it very straighforward
use strict;
use warnings 'all';
use feature 'say';
use EV;
use Time::Piece 'localtime';
STDOUT->autoflush;
my $one_second = EV::periodic 1, 1, 0, \&callback;
sub callback {
say "Periodic event at ", localtime(EV::now)->hms;
};
EV::run;
output
Periodic event at 10:27:36
Periodic event at 10:27:37
Periodic event at 10:27:38
Periodic event at 10:27:39
Periodic event at 10:27:40
etc.