{"id":7491,"date":"2020-02-19T16:19:43","date_gmt":"2020-02-19T22:19:43","guid":{"rendered":"https:\/\/wpengine.com\/support\/admin-ajax\/"},"modified":"2020-02-19T16:19:43","modified_gmt":"2020-02-19T22:19:43","slug":"admin-ajax","status":"publish","type":"support","link":"https:\/\/wpengine.com\/support\/admin-ajax\/","title":{"rendered":"WordPress and Admin AJAX"},"content":{"rendered":"

AJAX is a powerful tool that allows a website to extend its functionality and create a more seamless end-user experience. All AJAX calls in WordPress\u00ae route through the same location, called Admin AJAX.1<\/a><\/sup> Learn when not to use Admin AJAX and how to identify which AJAX actions are being made in excess.<\/p>\n\n\n\n\n\n\n\n

About Admin AJAX<\/h2>\n\n\n\n

AJAX is a JavaScript technology that allows data to be requested and returned on a page without actually refreshing the page. For example, in Google Maps, to view new map sections you don\u2019t need to load another page. As you move the map, it will load in new sections without having to fully reload the page.<\/p>\n\n\n\n

By default, WordPress routes all AJAX requests through an admin file located at wp-admin\/admin-ajax.php<\/code>. This is why, when referring to AJAX in WordPress, we call it \u201cAdmin AJAX\u201d.<\/p>\n\n\n\n

A common example of Admin AJAX in WordPress would be a checkout page on an ecommerce website. When you enter your shipping information, the site can query the database and display an updated price without<\/i> reloading the entire page.
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High Admin AJAX Usage<\/h2>\n\n\n\n

When AJAX is called anywhere on a WordPress website, the Admin AJAX file is requested: wp-admin\/admin-ajax.php<\/code>. On WP Engine, the wp-admin\/admin-ajax.php<\/code> file is uncached meaning it is generated new for each request and is never<\/i> served from cache storage. Uncached requests are significantly more resource-intensive than those served from cache.<\/p>\n\n\n\n

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Note<\/h3>\n\n\n\n

To review how WP Engine server caching works, we suggest checking out this guide<\/a>.<\/p>\n\n<\/div>\n\t\t<\/div>\n\t<\/div>\n<\/section>\n\n\n\n

While AJAX is a great tool, it can often run amok when set to make inefficient, unnecessary or a high number of calls. For this reason, it\u2019s important to use AJAX calls sparingly and only when completely necessary.<\/p>\n\n\n\n

For example, say that when a user visits a page it makes 5 Admin AJAX calls within a few seconds. Remember that AJAX calls are uncached, so all 5 must be processed by PHP anew. When 1 or 2 users are on the page, you may not see any impact with only 10 calls in a few seconds. However, when 5,000 visitors are on the page, you now have 25,000 uncached requests within just a few seconds. With enough visitors on the site pulling resources in this inefficient manner, the server will slow down (causing 504 errors) or even fail to complete requests completely (causing 502 errors).<\/p>\n\n\n\n

If you\u2019re seeing a large number of 504 or 502 errors on your site, it\u2019s highly possible that excess Admin AJAX requests are the culprit.<\/p>\n\n\n\n

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Note<\/h3>\n\n\n\n

Need a refresher on these error codes? Learn more about the 502 error here<\/a>. Learn more about the 504 error here<\/a>.<\/p>\n\n<\/div>\n\t\t<\/div>\n\t<\/div>\n<\/section>\n\n\n\n<\/a>\n\n\n\n\n\n

Admin AJAX Log<\/h2>\n\n\n\n

As all AJAX requests go through the wp-admin\/admin-ajax.php<\/code> file, requests are easy enough to track back to a single culprit with some additional logging enabled. If you\u2019re seeing a large amount of requests to wp-admin\/admin-ajax.php<\/code> within your access logs<\/a>, your next step will be to enable Admin AJAX logging.<\/p>\n\n\n\n

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Note<\/h3>\n\n\n\n

Before continuing, be aware that the Admin AJAX log can grow exponentially fast, which can cause issues for your site. Disable Admin AJAX as soon as possible in your troubleshooting process.<\/strong><\/em> We typically find 5-10 minutes to be a sufficient amount of time enabled.<\/p>\n\n<\/div>\n\t\t<\/div>\n\t<\/div>\n<\/section>\n\n\n\n

Admin AJAX logging can be enabled by adding the following line to the wp-config.php<\/code> file using either SFTP<\/a> or SSH Gateway<\/a>. Be sure to add this just below the section that says # WP Engine Settings<\/code>.<\/p>\n\n\n\n

define( 'WPE_MONITOR_ADMIN_AJAX', true );<\/code><\/p>\n\n\n\n

Once the line is added and the updated wp-config.php file has been uploaded back into the site, Admin AJAX logging will begin. We suggest timing 5 minutes before editing the file again to remove the line. During this time, perform any actions on your site where you\u2019ve seen slowness or errors, to ensure the process in question is logged during the test period.<\/p>\n\n\n\n

To disable Admin AJAX logging, open the wp-config.php<\/code> file again and either remove the define above, or update the value to false<\/code>.<\/p>\n\n\n\n

To review the log, download it at wp-content\/__wpe_admin_ajax.log<\/code><\/p>\n\n\n\n

Finally, be aware that admin AJAX logging only record POST requests. GET requests to admin-ajax.php<\/code> with arguments on the end are not logged. For example:
admin-ajax.php?action=do_something&that_something=should_be_cool<\/code>
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Troubleshoot Admin AJAX<\/h2>\n\n\n\n

We recommend troubleshooting high AJAX with SSH gateway<\/a>, if possible, because we have provided some commands to easily parse the log from your terminal below. This is the same approach WP Engine Support will take to troubleshoot the issue, as it\u2019s the most direct. All of the following commands will be run from the root of your website.<\/p>\n\n\n\n

With AJAX logging enabled, view the AJAX actions live as the request is made on the website:<\/b><\/p>\n\n\n\n