Why cron doesn't work to me?

Question

I'm on centOS 7 and I have a WordPress site. Due to some problems with the WordPress default wp-cron settings, I have chosen to do the cron tasks with my server instead. I have used this command:

wget http://www.example.com/wp-cron.php?doing_wp_cron=1 > /dev/null 2>&1

to run every 10 minutes. This works, every ten minutes it try to wget that page but it doesn't generate any outputs and the WordPress cron tasks are not executed.

Furthermore, if I try to open the page: http://www.example.com/wp-cron.php?doing_wp_cron=1 by myself on my browser, I get a blank page... Is this an error? I don't get any message in the Apache error log.

Answer 1

Do you have define('DISABLE_WP_CRON', true); set in wp-config? You need it to have the system cron fire up the wp-cron tasks. Go to the bottom of the database settings in wp-config.php, typically around line 37, and add it.

Then setup the system cron to fire up the wp-cron tasks:

*/5 * * * * wget -q -O - "http://example.com/wp-cron.php?t=`date +\%s`" > /dev/null 2>&1

#Sometimes it might be required to run PHP directly:
*/5 * * * * php /home/$USER/public_html/wp-cron.php

?doing_wp_cron is appended only automatically when you define ALTERNATE_WP_CRON as true in wp-config.php. Since you are disabling it entirely, you want to use the URL above instead or the 2nd method, which dispenses parameters.

If you're on a development environment and want to output debug information, calling it manually like that will show you your debug output.

Alternatively you can use PHP's built-in error_log function to log message strings to the error log for debugging. You'd need to use this in conjunction with WP_DEBUG settings.

If you need further help debugging it, try this question.

Answer 2

For people reaching this page because they use FastCGI and they can't find a way to run wp-cron.php

Issue with FastCGI:

When using FastCGI there is an issue that prevents wp-cron.php to be run from the browser.

To fix it, comment the following lines in your wp-cron.php:

Remember that it is not recommended to modify core WordPress files, so proceed only if you know what you are doing.

Before:

/* Don't make the request block till we finish, if possible. */
if (function_exists('fastcgi_finish_request') && version_compare(phpversion(), '7.0.16', '>=')) {
    if (!headers_sent()) {
        header('Expires: Wed, 11 Jan 1984 05:00:00 GMT');
        header('Cache-Control: no-cache, must-revalidate, max-age=0');
    }

    fastcgi_finish_request();
}

After:

/* Don't make the request block till we finish, if possible. */
//if (function_exists('fastcgi_finish_request') && version_compare(phpversion(), '7.0.16', '>=')) {
//    if (!headers_sent()) {
//        header('Expires: Wed, 11 Jan 1984 05:00:00 GMT');
//        header('Cache-Control: no-cache, must-revalidate, max-age=0');
//    }
//
//    fastcgi_finish_request();
//}