Varnish cache is cleared for the product and categories after an order is placed

[bmitchell-ldg]

Preconditions (*)

1. Magento 2.3.5
2. Varnish-6.0.6
3. Elasticsearch 6
4. PHP 7.2.30

Steps to reproduce (*)

1. Go to a category page and inspect the page and refresh until you see a x-cache HIT confirming that the page is being cached
2. Pick a simple product on that category page and on the product page inpect the page and refresh until you see the x-cache HIT confirming that the page is being cached
3. purchase that product
4. within the next couple of minutes you will see a purge request sent to varnish for that product i assume because the stock level changed (product saved)

• ReqMethod PURGE
• ReqURL /
• ReqHeader X-Magento-Tags-Pattern: ((^|,)cat_p_43(,|$))

5. refresh the category and product pages and see the x-cache MISS for both the category and product pages related to that specific product

The more categories the product is related to the more of an issue it causes for the website as all of the categories related to the product are being purged.

Expected result (*)

1. Since the actual stock level is not something that is displayed on the frontend as default, then i can't think of a reason why it should need to purge the cache everytime the quantity changes. I would have thought it would only carry out the cache purge if the stock status had changed because it would need to show the new instock/out of stock status on the product/category pages. Any website with fast selling products is never going to be able to keep the cache warm.

Actual result (*)

1. Placing an order causes all cache tags related to that product to be cleared.

Severity: S2

[m2-assistant]

Hi @bmitchell-ldg. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• Summary of the issue
• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

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[bmitchell-ldg]

@magento give me 2.4-develop instance - upcoming 2.4.x release

[magento-deployment-service]

Hi @bmitchell-ldg. Thank you for your request. I'm working on Magento instance for you.

[magento-deployment-service]

Hi @bmitchell-ldg, here is your Magento Instance: https://ba8cde84d445e9fcbadaf56604f12566-2-4-develop.instances.magento-community.engineering
Admin access: https://ba8cde84d445e9fcbadaf56604f12566-2-4-develop.instances.magento-community.engineering/admin_2661
Login: 83239c15
Password: af57ffb8d7f0

[bmitchell-ldg]

Hello,
I am unable to use varnish on the 2.4 testing instance to be able to fully replicate the issue we are seeing, but i have been able to see the same behaviour using the built in cache on product pages.

*Product Page Cache Tests
I have added screenshots below

• Screenshot shows the page load on a cached page
• I have then placed an order for the product
• a couple of minutes after the order is placed, you can see the cache has been purged for that product, you can see it by the page load time increase when inspecting the network tab.

[bmitchell-ldg]

@magento give me 2.4-develop instance - upcoming 2.4.x release

[magento-deployment-service]

Hi @bmitchell-ldg. Thank you for your request. I'm working on Magento instance for you.

[magento-deployment-service]

Hi @bmitchell-ldg, here is your Magento Instance: https://ba8cde84d445e9fcbadaf56604f12566-2-4-develop.instances.magento-community.engineering
Admin access: https://ba8cde84d445e9fcbadaf56604f12566-2-4-develop.instances.magento-community.engineering/admin_6ac7
Login: b181955d
Password: e69706295bad

[gwharton]

Could be because of "only X left" functionality. If so it should only clear cache if qty is less than threshold I guess.