WordPress Cron Jobs

WordPress Cron Jobs

WordPress handles scheduling time based background processes as an atypical Cron Job.

Generically, it works by checking a list of scheduled tasks on pre-determined intervals if they should run every page load. Anything due will run during that page load.

Errors can occur if your site does not recieve alot of traffic, receives little traffic during certain time frames, or if there are potential coding issues present in the site.

Why use it?

• WordPress core and many plugins need a scheduling system to perform time-based tasks. However, many hosting services are shared and do not provide access to the system scheduler.
• Using the WordPress API is a simpler method for setting scheduled tasks than going outside of WordPress to the system scheduler.
• With the system scheduler, if the time passes and the task did not run, it will not be re-attempted. With WP-Cron, all scheduled tasks are put into a queue and will run at the next opportunity (meaning the next page load). So while you can’t be 100% sure when your task will run, you can be 100% sure that it will run eventually.

I decided that I cannot rely on the built-in WordPress Cron to work properly when scheduled, primarily because I cannot sit and watch traffic to re-schedule the jobs around those timeframes.

So… instead of relying on that, I wrote the following bash script to take care of all sites on my server.

Simply create a cron job to run it every 10 or 15 minutes, and change the _PATH to your liking.

#!/usr/bin/env bash

# hold the primary WP CLI command
WP_CLI="wp --allow-root --path="

# hold the starting path
_PATH=/home/*/htdocs/*

# loop over our home directory for the htdocs folder...
for d in $_PATH; do
    
    # now hold the formatted command
    CMD=$WP_CLI$d/;

    # check if this site is indeed a wordpress website
    if $CMD core is-installed 2>/dev/null; then

        # check if the site is a network 
        if $CMD core is-installed --network 2>/dev/null; then

            # get the networks list of uri's
            _uris=$( $CMD site list --field=url )

            # loop over the sites
            for _uri in $_uris; do
                
                # fire off the sites cron
                $CMD cron event run --all --due-now --url="$_uri" & 

            done;

        # otherwise, we aren't in a network
        else
            
            # get the site's uri
            _uri=$( $CMD option get siteurl );
            
            # fire off the sites cron
            $CMD cron event run --all --due-now --url="$_uri" & 

        fi;

    fi;
    
done;