Problem with product quantity being exceeded

Hi,

If the stock of the product is 0 at the moment the order is created, then the order creation will be cancelled and the products removed from the cart (HikaShop 3 or newer with "checkout legacy" setting turned off).
So the only way to get products oversold is if you configured your HikaShop to update the stock of the product when the order is confirmed and not when the order is created. In that case, it's possible to create plenty of orders of a product even if the stock of the product is 1. As long as one of the orders is not paid (and thus not yet confirmed), the stock will stay at 1.

So you need to check the setting "Update the product stock on confirmed status" and make sure it is turned off so that the stock is updated when the order is created, not when it is confirmed.
In such case, you might actually have left overs if people don't pay for their orders. So you can have the "order auto cancel" plugin cancel automatically the created orders not paid after a certain amount of time. That will give back the stock upon cancellation of the orders.

Hi,

Having the legacy checkout to no is good. That means you're using the new checkout. However, it shouldn't have an impact on the stock management.

Well, if the load is really high and that several people order the same product at the same time, it's potentially possible that when a customer clicks on "finish" on the checkout, between the time when the cart is loaded into memory and the stock checks are done, and the time the order is created in the database and the stock is updated, someone else could have clicked on the "finish" button and the cart be already loaded in memory with the stock checks already already done.
This normally happens in a fraction of a second, so the probability of that happening is really low, but not impossible. One percent of oversell seems quite hight to me but if the server is running to a crawl, then that fraction of a second might transform into a few seconds and in that case, that could explain that one percent of oversell.
In that case, I see several things you can do:
- use a more powerful server which can better take in the load.
- The email sending process can require a lot of resources and can potentially be the main cause of the server load. So you might want to see how this can be optimized (like using a 3rd party email sending service, etc).
- You could potentially write a plugin implementing the onAfterCartProductsLoad trigger and directly update the stock at that point if the parameters in $_REQUEST indicate that the "finish" button has been clicked and then reupdate the stock back after the order is created to avoid double decrementing the stock.