Prevent 422 Insights Event - Add to Cart with Discount

[PromInc]

Summary

Adding a product to the cart may trigger a PHP and Algolia error due to the discount amount being too large due to improper math by PHP.

PHP Version

php -v
PHP 8.2.28 (cli) (built: Mar 13 2025 18:13:24) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.2.28, Copyright (c) Zend Technologies
    with Zend OPcache v8.2.28, Copyright (c), by Zend Technologies
    with Xdebug v3.4.2, Copyright (c) 2002-2025, by Derick Rethans

Result

PHP Error

This error is thrown in var/log/system.log

main.CRITICAL: Unable to send add to cart event due to Algolia events model misconfiguration: Discount must be a valid decimal number and total length must be no longer than 16 characters [] []

Algolia Error

A 422 status code is returned in the Algolia Events Debugger.

Here using xdebug in PHPStorm we can see what is happening.

The product discount amount should be 0.06. But PHP comes up with the value of 0.059999999999999 instead.

• floatval($item->getProduct()->getPrice()) = 23.99
• $this->getQuoteItemSalePrice($item) = 23.93
• floatval($item->getProduct()->getPrice()) - $this->getQuoteItemSalePrice($item) = 0.059999999999999

I don't understand this math and how it fails... 🤷‍♂️ But we can protect against it with a round(). (maybe it should be added to other methods in this class but I didn't observe issues from those at this time)

The discount amount on this product is using the core Magento Customer Group Price feature - adding the discount amount to table catalog_product_entity_tier_price.

SELECT * FROM catalog_product_index_price WHERE entity_id = 5981 AND customer_group_id = 22;
 entity_id | customer_group_id | website_id | tax_class_id | price     | final_price | min_price | max_price | tier_price 
-----------+-------------------+------------+--------------+-----------+-------------+-----------+-----------+------------
      5981 |                22 |          2 |            2 | 23.990000 |   23.930000 | 23.930000 | 23.930000 |  23.930000 

SELECT * FROM catalog_product_entity_tier_price WHERE entity_id = 5981 AND customer_group_id = 22;
 value_id | entity_id | all_groups | customer_group_id | qty    | value     | website_id | percentage_value 
----------+-----------+------------+-------------------+--------+-----------+------------+------------------
   490854 |      5981 |          0 |                22 | 1.0000 | 23.930000 |          0 |           [NULL]