[wp-trac] [WordPress Trac] #21938: Add "no-store" to Cache-Control header to prevent history caching of admin resources

[WordPress Trac]

#21938: Add "no-store" to Cache-Control header to prevent history caching of admin
resources
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 Reporter:  soulseekah                    |       Owner:  johnbillion
     Type:  enhancement                   |      Status:  reopened
 Priority:  normal                        |   Milestone:  6.3
Component:  Administration                |     Version:  3.4
 Severity:  normal                        |  Resolution:
 Keywords:  needs-dev-note needs-testing  |     Focuses:  performance,
                                          |  privacy
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Changes (by johnbillion):

 * keywords:  has-patch has-testing-info needs-dev-note => needs-dev-note
     needs-testing
 * status:  closed => reopened
 * focuses:  privacy => performance, privacy
 * resolution:  fixed =>
 * severity:  minor => normal


Comment:

 The load should not increase significantly during tests because the `no-
 store` directive affects whether a response can be fetched from the
 browser cache when navigating the browser history. If the tests aren't
 making use of the browser history then there should be no change to the
 load on the server. The browser should still continue to cache CSS and JS
 files that are loaded on the page.

 There could well be a bug in the test driver or test suite which means
 this is not the case and additional load is being placed on the server,
 therefore increasing response times and causing timeouts. I'm also not
 familiar enough with the e2e test suite to know for sure.

 I'm going to reopen this ticket and tag it with the performance focus in
 case there is a degradation or regression that's gone unnoticed.

 == Performance testing steps ==

 * Request multiple successive pages in the wp-admin area
 * Ensure that JS, CSS, and image assets loaded on the pages remain cached
 appropriately between successive requests
 * Ensure the browser back button causes the page to be re-requested from
 the server and not served from the cache, but that JS, CSS, and image
 assets are served from the cache
 * Test both with `SCRIPT_DEBUG` enabled and disabled

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Ticket URL: <https://core.trac.wordpress.org/ticket/21938#comment:31>
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