Probably something to document rather than a bug or anything, but it is worth noticing that the language switcher block provided by core has a hardcoded max age to 0 until #2232375: Support CacheOptionalInterface in BlockViewBuilder, use it in language switcher block to prevent max-age 0 bubbling is fixed,
This means that any site that has language switcher enabled and set to a common area (like the header of the page) will be serving all pages with max age 0 as soon as Cache Control Override module is enabled.
It seems that book navigation does the same thing, but that's probably used less.
Comments
Comment #2
dpiThanks for the heads up.
Occasionally bugs like these pop up, like the previous long-standing bug with admin toolbar: #2949457: Enhance Toolbar's subtree caching so that menu links with CSRF token do not need one subtree cache item per session
Maybe a tag can be created to group these together? which we can link off from the project page. Might be trouble tracking these bugs from the project page, readme, or otherwise.
Comment #3
prudloff commented#2232375: Support CacheOptionalInterface in BlockViewBuilder, use it in language switcher block to prevent max-age 0 bubbling has been fixed so the language switcher should not be a problem anymore.