Have you considered using a closure for this?  It sounds like you want the value to not change for at least 10 minutes after the first time you create the value; if that's the case, I'd suggest something like:

#!/usr/bin/perl -w

# Strict
use strict;
use warnings;

# Test code
my $psub = same_value_for_time_period(5);
while (1) {
    my $x = $psub->();
    printf "Value is %s\n", $x;
    sleep 1;
}

# Subroutines
sub same_value_for_time_period {
    my ($duration) = @_;            # Eg. 600 = 10 minutes
    my $start_time = time;
    my $value = get_new_value();
    sub {
        my $now = time;
        if ($now - $start_time < $duration) {
            return $value;
        } else {
            $start_time = $now;
            $value = get_new_value();
        }
    }
}

sub get_new_value {
    my $value;

    # Your code for creating a new value here ...
    $value = rand 1000;

    return $value;
}
[download]

Here, you call the subroutine same_value_for_time_period with a duration (the number of seconds you wish the value to remain constant for).  It returns a pointer to a closure; a subroutine which, each time you call it after it's first created, gives you the same value within the specified duration, and then changes after that.  The subroutine get_new_value is called when the duration is up, to give a new value.  As you can see, I've tested it for a short duration (5 seconds), and just using a random number whenever the value changes.

Is that the kind of thing you're looking for?

This code has some interesting ideas for running a server returning such value; but; this would mean it isn't a stateless number calculated for that moment ; if I restart the proces (which happens in my cgi's, I don't use mod_perl (yet)) it will change numbers

It would give me the same results if I would do a time() and change the last 2 digits to a 00 and use that as "current string for this time"; what I need is a sort of "random-but-still-the-same for 10 minutes".

Next to that the "five-before-twelve problem" is still in the air with both methods...

I'm unable to see how you can choose a stateless value which is guaranteed to not change for a finite period of time.

Since the number is stateless, it must depend on some external reference (eg. a timet).  However, you want the value to change, there's no way to avoid getting the value at some arbitrary number of seconds N prior to the number changing, for some N less than the duration you're interested in (here 600 seconds).  So unless I've misunderstood your requirements, I don't see how you what you're looking for is possible.

Now, if you're willing to accept numbers which are the same for a 10-minute period, just use:

my $value = int(time / 600);
[download]

But, of course, you still have the problem of having the value change very soon after you choose it.

---

s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/

That would involve writing to the disk; which is a overhead I want to save for the perlscript processing ; it's already too heavy as it is ; I wonder if there is any way I can "modularize" loading and deloading of certain modules ...

That would involve writing to the disk; which is a overhead I want to save for the perlscript processing...

In a network application? You have much bigger overheads, unless you've overcome the speed of light.

Memoize caches to memory by default, not disk. Also Cache-Cache has Cache::MemoryCache you can use instead of Cache::FileCache

As only the cron job is allowed to write a new value you do not get into trouble through race conditions.

Update: Reading through all messages till now, I might have misunderstood your question. If I have it right now, you need a value which stays the same for x minutes PER USER. It looks to me that what you need can be done through a cookie, which you set to expire in x minutes.

You may be looking for Tie::Scalar::Timeout. If you really do want a subroutine to be returning the value you could build a closure around the sub, and declare the tied variable into the broader-scope of the closure. It can be tied within the sub, as needed.

this is for mod_perl ;

I'm using normal cgi sessions. It can also be used for a added security to downloaders ; because the path changes as soon as the ip / user / "token" or "ticket" expires.

I'd need such thing as this, but based on a formula of information including an expiration value ; which is now set to 900 currently (15 minutes).

The problem is, since there is no mod_perl:

1. I have no statefull connection
2. hereby the system will have to "guess" it by itself and do the appropriate addings/encrypting and powdering afterwards.
3. it introduces a "five-before-twelve" bug which means; if you are 1 minute before the expiration timeframe of 900 seconds ends,
   • you either have to be fast entering your password and bark like a dog 3 times or
   • have the inconvience of seriously discomforted/discombulated electrons; because "your logintime just ended" ... awwww

this is for mod_perl

Don't count on it! Even in mod_perl you are never guaranteed that your request will be handled by the same worker/thread as before.

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law

this is for mod_perl ;

Why didn't you say so in the first place... didn't seem relevant at the time?




Dave

Update: Oops, that's 10 hours. 10 minutes would just be 10*60. Thanks, freakingwildchild!

10 * 60 * 60 would give 36000; thats an awfull long time for the "ticket" to expire :)