Say you want to run a cron job 10 times (or so) in a day at random times.

Here’s my solution:

1. Create a probability test that gives a 10% probability of the outcome you want

$p = mt_rand(1,10);

2. Add in a bit of extra randomness with a short sleep

$s = mt_rand(60,300);
sleep($s);

giving:

$p = mt_rand(1,10);

if ($p != 1) {

exit;

} else {

$s = mt_rand(60,300);
sleep($s);

Your stuff here…

}

3. Run your cron job 4 times an hour, 24 hours a day

*/15 * * * * /usr/bin/php myscript.php

At this, your cron job will run 96 times per day, and execute 1 in 10 of those times, which gives you 9 to 10 executions per day at random times.

OK, its not totally random, and you can’t guarantee the number of executions, but if you have  fixed number of executions per day, that’s not really random, is it?

Nod, nod, wink, wink….

This entry was posted on Monday, March 30th, 2009 at 11:29 pm and is filed under Linux. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.