How to code schedule / cron job

Question

I am using wp_schedule_event to hourly insert items from an rss news feed into my client's blog. Here is how I am setting it up in my functions.php:

add_action('init', function(){
     $timescheduled = wp_next_scheduled('update_feed');
     wp_unschedule_event($timescheduled, 'update_feed');

    if (!wp_next_scheduled('update_feed'))
    wp_schedule_event(time(), 'hourly', 'update_feed');
});

add_action('update_feed', 'update_fashion_news');

/* rest of the code for updaring feed goes here */

So first I unschedule it and then schedule the event. Now this seems to work some days and other times it doesn't. Is the unscheduling part necessary? Am I doing this right? What I want to know is:

1. Am I using my function calls in the right order?
2. Are the schedule and unschedule calls cancelling each other out?

Here is the full code in a gist if you want to see it: https://gist.github.com/3984658

Answer 1

Inspect your Schedules

The best way to learn coding is to turn debug on and simply inspect your output. If you want to dig deeper, then you often need a custom tool that allows you to inspect the result fast and nicely, readable formatted.

I wrote a plugin for some other answer, that helps you inspecting the WP "Cron Jobs"/Schedules. You can grab it on GitHub as Gist.

Here's what the output looks like.

Forks

@StephenHarris forked the plugin, which is also available as Gist.

Primary difference between this plug-in and the original, is that this displays each seperate cron-job even when two or more share the same hook (and arguments).

^{- Stephen Harris in the plugins comment}

Answer 2

I second Kaiser as you need to do the check, BUT also, check the visitors pattern to the site. The word press cron scheduler is triggered by visits, so, if your site is not receiving regular visitors around the clock it will miss schedules and the cron will not run.

Hope this helps :)