How can I calculate business/SLA hours with iterating over each second? - perl

Question

Before I spend a lot of time writing the only solution I can think of I was wondering if I'm doing it an inefficient way.
Once a support ticket is closed, a script is triggered, the script is passed an array of 'status-change-events' that happened from call open to close. So you might have 5 changes: new, open, active, stalled, resolved. Each one of these events has a timestamp associated with it.
What I need to do is calculate how much time the call was with us (new, open, active) and how much time it was with the customer (stalled). I also need to figure out how much of the 'us' time was within core hours 08:00 - 18:00 (and how many were non-core), and weekends/bank holidays count towards non-core hours.
My current idea is to for each status change, iterate over every second that occurred and check for core/non_core, and log it.
Here's some pseudo code:
time_since_last = ticket->creation_date
foreach events as event {
time_now = time_since_last
while (time_now < ticket->event_date) {
if ticket->status = stalled {
customer_fault_stalled++
} else {
work out if it was our fault or not
add to the appropriate counter etc
}
time_now++
}
}
Apologies if it's a little unclear, it's a fairly longwinded problem. Also I'm aware this may be slightly off of SO question guidelines, but I can't think of a better way of wording it and I need some advice before I spend days writing it this way.

Answer 1

I think you have the right idea, but recalculating the status of every ticket for every second of elapsed time will take a lot processing, and nothing will have changed for the vast majority of those one-second intervals
The way event simulations work, and the way I think you should write your application, is to create a list of all events where the status might change. So you will want to include all of the status change events for every ticket as well as the start and end of core time on all non-bank-holiday weekdays
That list of events is sorted by timestamp, after which you can just process each event as if your per-second counter has reached that time. The difference is that you no longer have to count through the many intervening seconds where nothing changes, and you should end up with a much more efficient application
I hope that's clear. You may find it easier to process each ticket separately, but the maximum gain will be achieved by processing all tickets simultaneously. You will still have a sorted sequence of events to process, but you will avoid having to reprocess the same core time start and end events over and over again
One more thing I noticed is that you can probably ignore any open status change events. I would guess that tickets either go from new to open and then active, or straight from new to resolved. So a switch between with your company and with the customer will never be made at an open event, and so they can be ignored. Please check this as I am only speaking from my intuition, and clearly know nothing about how your ticketing system has been designed

Answer 2

I would not iterate over the seconds. Depending on the cost of your calculations that could be quite costly. It would be better to calculate the borders between core/outside core.
use strict;
use warnings;
my $customer_time;
my $our_time_outside;
my $our_time_core;
foreach my $event ($ticket->events) {
my $current_ts = $event->start_ts;
while ($current_ts < $event->end_ts) {
if ($event->status eq 'stalled') {
$customer_time += $event->end_ts - $current_ts;
$current_ts = $event->end_ts;
}
elsif (is_core_hours($current_ts)) {
my $next_ts = min(end_of_core_hours($current_ts), $event->end_ts);
$our_time_core += $next_ts - $current_ts;
$current_ts = $next_ts;
}
else {
my $next_ts = min(start_of_core_hours($current_ts), $event->end_ts);
$our_time_outside += $next_ts - $current_ts;
$current_ts = $next_ts;
}
}
}

Answer 3

I can't see why you'd want to iterate over every second. That seems very wasteful.
Get a list of all of the events for a given ticket.
Add to the list any boundaries between core and non-core times.
Sort this list into chronological order.
For each consecutive pair of events in the list, subtract the later from the earlier to get a duration.
Add that duration to the appropriate bucket.
And the usual caveats for dealing with dates and times apply here:
Use a library (I recommend DateTime together with DateTime::Duration)
Convert all of your timestamps to UTC as soon as you get them. Only convert back to local time just before displaying them to the user.