wp_schedule_single_event does not call my action

Question

I have created the following action:

add_action( 'test_action', 'test_action' );

function test_action() {
    error_log( 'test_action' );
}

And am calling it like this:

error_log( 'send_test_email_in_background:START' );

wp_schedule_single_event( time(), 'test_action' );

error_log( 'send_test_email_in_background:END' );

What I receive in the apache error log file is this:

[17-Sep-2015 11:09:35 UTC] send_test_email_in_background:START

[17-Sep-2015 11:09:35 UTC] send_test_email_in_background:END

This works exactly the same in development on my Windows PC (running WAMP) than it is on Production (running Linux in AWS). Also, if I schedule the single event 5 minutes in the future (time() + 300) it shows in my "Debug Bar Cron" plugin as being available to run in 5 minutes time and it appears to run just fine. So it appears that the CRON jobs are being created but for some reason they are not actually calling the action when running? Has anyone else had this problem or have an insight into it?

Answer 1

Because you're scheduling the event - even though it's set to run immediately (i.e. with time()), it won't fire until a second request.

So that log output is entirely expected. Try running it again, removing the code, then run once more - you should get:

[time] test_action

Answer 2

If you have used a template for WordPress admin functions, you may have been inclined to insert your cron jobs inside your admin class.

If, at the same time, your main code has an IF statement like this:

if (is_admin()) {
    foreach( glob ( PLUGIN_DIR . "/admin/*.php" ) as $filename ) {
       require_once( $filename );
    }
}

Then this will mean the admin files will not be loaded for cron. is_admin() returns true only for when admins are visiting the wp-admin pages.

If this is the case, you need to separate your add_action out to a file that always gets called by your plugin. You can still have your actual cron function inside your class if you wish, using a static function.