Missing Vary-Cookie makes pages uncachable (for Varnish)

[rommelfreddy]

Preconditions and environment

• Magento version: >= 2.4.8
• not logged in customer

Steps to reproduce

Just setup Varnish with the default-configurations

Expected result

Cacheable Pages, like CMS, Catalog and so on, should be cached and stored in the Varnish-Cache

Actual result

Magento will always make the response uncachable by calling Magento\Framework\App\Response:: setNoCacheHeaders

Additional information

In commit d6c05bd, logic was added to make the response uncacheable if the Vary cookie does not match the actual (generated) vary string.

While this makes sense in principle, it also causes all pages to become uncacheable whenever no Vary cookie is set — which is always the case on the very first request.

Additionally, this situation also occurs when Varnish requests the backend without sending the Vary cookie. As a result, this bug affects all ESI requests as well.

This issue should be treated with high priority, as it effectively prevents full-page caching with Varnish from functioning correctly.

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For anyone encountering this problem, I’ve created a temporary patch until an official fix is released: patch

Please use this patch with care and test your application thoroughly.

Release note

No response

Triage and priority

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.

[m2-assistant]

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[m2-assistant]

Hi @engcom-November. Thank you for working on this issue.
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[m2-assistant]

Hi @engcom-Bravo. Thank you for working on this issue.
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[m2-assistant]

Hi @engcom-Hotel. Thank you for working on this issue.
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• 1. Verify that issue has all the required information. (Preconditions, Steps to reproduce, Expected result, Actual result).
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• 4. Verify that the issue is reproducible on 2.4-develop branch
  Details

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[engcom-Hotel]

Hello @rommelfreddy,

Thank you for the collaboration!

We have tried to reproduce the issue in the latest development branch i.e. 2.4-develop but the issue seems not reproducible for us, as you mentioned the user needs to be a guest user (not logged in), when the first time user tries to any page like homepage, catalog page, etc. the value of x-magento-cache-debug is showing as MISS but the next time it is showing as HIT, which seems to be an expected behaviour.

Please let us know if we missed anything.