Title: Extremely high CPU usage Last modified: January 27, 2025 --- # Extremely high CPU usage * [gordonzed](https://wordpress.org/support/users/gordonzed/) * (@gordonzed) * [1 year, 4 months ago](https://wordpress.org/support/topic/extremely-high-cpu-usage-3/) * To be very honest, I don’t remember installing this plugin, nor do I know what functionality it was providing, if any (I suspect one of our fulfillment staff installed it, but I’m clearly to blame if their user role was able to do so), so this is less of a support request and more of an issue report for the benefit of the dev. There’s also always the chance that I did install it, but so long ago that I don’t remember, in which case I’ll be keeping an eye out for side effects caused by deactivation. * Our store went down at 1:00pm today. MySQL’s process had pinned our CPU at 100%, causing a complete denial of service. I migrated to a server with more resources so I could get back up and running and properly assess the situation, but within 10 minutes, it was back up near 100% (not to the point of denial of service this time, but things were extremely slow). The answer lay in the slow execution logs. This query was frequently taken over 2 minutes to complete, and almost single- handedly causing 90+ percent of our CPU usage: * ```wp-block-code Query_time: 137.354499 Lock_time: 0.000372 Rows_sent: 2735 Rows_examined: 6654560# Rows_affected: 0 Bytes_sent: 264369SET timestamp=1738008229;SELECT *-- ,(SELECT GROUP_CONCAT(DISTINCT post_title) FROM wp_posts WHERE FIND_IN_SET(ID,product_ids)>0)productFROM (SELECT p.ID post_id,post_title coupon_code,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='product_ids' LIMIT 1)product_ids,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='exclude_product_ids')exc_prds,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='product_categories')cats,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='exclude_product_categories')exc_cats,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='individual_use' LIMIT 1)individual,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='coupon_amount' LIMIT 1)coupon_amount,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='customer_email' LIMIT 1)c_email,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='_wc_min_qty' LIMIT 1)min_qty,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='_wc_max_qty' LIMIT 1)max_qty,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='_wc_qty_ntf' LIMIT 1)qty_ntf,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='_wc_min_qty_ntf' LIMIT 1)min_qty_ntf,(SELECT meta_value FROM wp_postmeta WHERE post_id=p.ID AND meta_key='_wc_max_qty_ntf' LIMIT 1)max_qty_ntf,(SELECT meta_key FROM wp_postmeta WHERE post_id=p.ID AND meta_key LIKE '_wc_%_apply' AND meta_value='yes' ORDER BY meta_key LIMIT 1)apply,DATE_FORMAT(FROM_UNIXTIME(x.meta_value),'%m-%d-%Y')exp_date,CASE WHEN FROM_UNIXTIME(x.meta_value)=NOW())aWHERE(individual='yes' OR apply IS NOT NULL OR c_email IS NOT NULL)ORDER BY individual DESC,exp,CAST(coupon_amount AS SIGNED) DESC; ``` * As you can see, our database is quite large. It’s a WooCommerce store with 2+ years of orders/customers, and a large line of 300+ individual products, so I suspect this may not cause issues for new/small stores, but it seems that at a certain database size, the scaling can get wildly out of hand. I do have quite a bit of custom functionality regarding coupons, so it’s more than possible that contributed to the problem, depending what woocommerce hooks this plugin is making use of. Viewing 2 replies - 1 through 2 (of 2 total) * Plugin Author [RLDD](https://wordpress.org/support/users/rermis/) * (@rermis) * [1 year, 4 months ago](https://wordpress.org/support/topic/extremely-high-cpu-usage-3/#post-18268629) * Thank you for reporting this issue and providing such a detailed explanation of the situation. * This plugin is designed to retrieve all coupons that qualify to be auto-applied in a single sweep, avoiding redundant and looping queries that typically consume additional resources. The query specifically targets published posts with the` shop_coupon` post type that have not expired, ensuring quick execution under normal circumstances. * Have you tried executing this query directly on your database? In our tests within an established WooCommerce environment, the query consistently executes in approximately** 0.004 seconds**. If you find this to differ when running a query profile please let me know, I would be happy to look into this further -as it could perform differently in other environments. * There are certain scenarios that could lead to prolonged query execution times, such as: 1. **High Traffic or DDoS Activity** If a malicious or unusually high volume of traffic targeted your cart page, it could trigger this query repeatedly in rapid succession, straining server resources. 2. **Large or Unindexed Tables** In stores with large datasets (e.g., extensive coupon metadata), insufficient indexing on key columns (e.g., `meta_key` in ` wp_postmeta`) could significantly impact query performance. 3. **Custom Code or Hooks** If custom functionality modifies or hooks into WooCommerce coupon queries, it might inadvertently add complexity or cause conflicts. Reviewing any custom functions tied to coupon processing could help identify potential contributors. * Please let me know if you continue to look into this incident. If any issues are identified with a part of the query that causes extended execution, or if you find that any part of the query is omitted and it runs faster, I can definitely take this information and improve the plugin. For example, if you run the query without all the columns (or without the LEFT JOIN) and it’s performance changes, this would be helpful to know. Or if you exclude any conditions past WHERE and it runs differently. I look forward to finding the root issue with your help. Thank you! * Thread Starter [gordonzed](https://wordpress.org/support/users/gordonzed/) * (@gordonzed) * [1 year, 4 months ago](https://wordpress.org/support/topic/extremely-high-cpu-usage-3/#post-18269737) * I’d be happy to do a bit of investigating when I have some free time. I do have a custom plugin that generates new coupons when users spin a prize wheel, although I can’t imagine why this plugin would be interacting there. I also have a far less elegant bit of code that auto-deletes unclaimed prize wheel coupons after 24 hours, using WP_query if I remember correctly, and something tells me that might be the more likely culprit. * I’ll try and make some time to mess around with this tomorrow after work if possible( later today actually; I had no idea it was anywhere near 6:45am 🫠). - This reply was modified 1 year, 4 months ago by [gordonzed](https://wordpress.org/support/users/gordonzed/). Reason: minor aesthetic edit Viewing 2 replies - 1 through 2 (of 2 total) The topic ‘Extremely high CPU usage’ is closed to new replies. * ![](https://ps.w.org/woo-auto-coupons/assets/icon-256x256.png?rev=3405507) * [Auto Coupons for WooCommerce](https://wordpress.org/plugins/woo-auto-coupons/) * [Frequently Asked Questions](https://wordpress.org/plugins/woo-auto-coupons/#faq) * [Support Threads](https://wordpress.org/support/plugin/woo-auto-coupons/) * [Active Topics](https://wordpress.org/support/plugin/woo-auto-coupons/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/woo-auto-coupons/unresolved/) * [Reviews](https://wordpress.org/support/plugin/woo-auto-coupons/reviews/) ## Tags * [cpu-usage](https://wordpress.org/support/topic-tag/cpu-usage/) * [server resources](https://wordpress.org/support/topic-tag/server-resources/) * 2 replies * 2 participants * Last reply from: [gordonzed](https://wordpress.org/support/users/gordonzed/) * Last activity: [1 year, 4 months ago](https://wordpress.org/support/topic/extremely-high-cpu-usage-3/#post-18269737) * Status: not a support question