[RESOLVED] Cron Script that run every one min. (PHP) help

Nileshp

Hey,

have a tech question for the root server.

currently i have added a cron script that run a filename.php script every 1 min (applys watermark to set of images)

I have issue where the Cron script is not waiting until the first job gets done .

for example i have one Cron job that run every 1min (run a PHP script file). issue is the Cron job is not wait until the first php script run is finished it just keeps triggering it over and over. any way to make Cron scripts wait until the job is done running before it try to run again? i understand normally its suppose to do that. yet for me it just run script every 1min even if its done running or not, causing issue. any options?

any options or method i may use so cron script want keep overlapping its task every one Min. ,Cron job should wait until its done running normally?, so if 2min comes up it want re trigger unless its already running.

thanks for any help! cheers!

wilku

You need to create some sort of a check that only one script can run at a time.
I'd do thist that way:
- when script start to run, it creates some file
- when it finishes it deletes the file
Now at the beginning of the same script (before creating this file) check if the file isn't already created and proceed only if it isn't. Something like:

<?php
$filename = '/tmp/scrip_running';
//check if another instance of this script is running
if (is_file($filename)) exit;

//if it isnt - create the file
$f = fopen($filename,'w+');
fclose($f);

//do your stuff here

//delete the file after script finishes to allow script running
unlink($filename);
?>

MarkR

A race-condition free script would instead open a file for writing (somewhere) and acquire an exclusive lock (with flock and LOCK_EX) on it. Lock in a nonblocking fashion, if it fails, another process has an exclusive lock, so you should exit.

This would guarantee mutual exclusion.

However, you may instead want to refactor your application so it uses a constantly-running process if stuff is being done that often / intensively.

Mark

Nileshp

Yes, thanks much for reply wilku, and Mark.

Yes, i think i will have to use your suggestion Wilku, and come up lock method of unlink file method, thanks for your tips and suggestions.

have a good weekend!
Nilesh