Question

My environment:
wordpress –> myplugin
in myplugin I use wp-loaded action to trigger my cronfunc to run
my cronfunc pseudo-code:

add_action('wp_loaded','cronfunc');

    function cronfunc()
    {
        if(defined('IN_MY_CRON_FUNC'))
            return;
        define('IN_MY_CRON_FUNC',true);
        if nowtime - get_option('last_do_work_time') > 3600:
            update_option('last_do_work_time',nowtime);
            run cronjob
    }

The problem is sometimes cronfunc will run twice!
Somebody tell me why?

Answer 1

I can’t seem to get it to load twice on a manually set plugin. Here is the code:

<?php
/*
Plugin Name: test
Plugin URI: http://localhost
Description: nothing really
Version: 00.001
Author: somebody
Author URI: http://localhost
*/
add_action('wp_loaded','cronfunc');
function cronfunc() {
    $myFile = (pathinfo(__FILE__));
    $myFile = $myFile['dirname']."/testFile.txt";
    $now = microtime(true);
    if ( $now - get_option('last_do_work_time') > 3 ) { #I set to 3 seconds to test
        $fh = fopen($myFile, 'a+') or die("can't open file");
        fwrite($fh, microtime(true)." - ".$now - get_option('last_do_work_time')."-\n");
        fclose($fh);
        update_option('last_do_work_time',$now);
    }
}
?>

Saved as test.php and put into a folder in plugins and activated it. Does it happen a lot or just once in a while? It’s possible that they are getting past IF before being updated again. If that is the case, you may need to lock the option and wait or skip if it’s already being run. You might need to use semaphores or create something like it using the database… maybe you could use wordpress options to define a kind of mutex or something. DEFINE() isn’t going to help, because if it’s run again side by side, then they won’t affect each other.

here is probably a bad way to do it, but it might work for now:

<?php
/*
Plugin Name: test
Plugin URI: http://localhost
Description: nothing really
Version: 00.001
Author: somebody
Author URI: http://localhost
*/

function wplock_release($id='check_cronfunc') {
    delete_option($id);
}
# not the best, but might work
function wplock_aquire($id='check_cronfunc') {
    $guid = com_create_guid(); #maybe just need uniqid or something, but just testing stuff
    # check if anyone else has lock and set, not sure if we can force lines inside php
    if ( get_option($id) !== false
        || !update_option($id,$guid)
        || get_option($id) != $guid )
    { 
        return false;
    }
    register_shutdown_function(wplock_release($id)); # probably don't need this
    return true; # maybe just return true or something
}


add_action('wp_loaded','cronfunc');
function cronfunc() {
    $myFile = (pathinfo(__FILE__));
    $myFile = $myFile['dirname']."/testFile.txt";
    $now = microtime(true);
    if ( wplock_aquire() ) {
        if ( $now - get_option('last_do_work_time') < 3 ) { # less than 3 seconds
            wplock_release();
            return;
        }
        wplock_release();
    } else {
        return;
    }

    $fh = fopen($myFile, 'a+') or die("can't open file");
    fwrite($fh, microtime(true)." - ".$now - get_option('last_do_work_time')."-\n");
    fclose($fh);
    update_option('last_do_work_time',$now);
}
?>

EDIT: put the lock around the option and returned if can’t get… a little sloppy, but just for the idea