Vary Header should not be controlled by the client #138
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skryukov
commented
Oct 19, 2024
| @@ -16,7 +16,11 @@ def initialize(component, controller, request, response, render_method, props: n | |||
| end | |||
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| def render | |||
| @response.set_header('Vary', [@request.headers['Vary'], 'X-Inertia'].compact.join(', ')) | |||
| if @response.headers["Vary"].blank? | |||
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To be honest, I prefer the original functional approach, but it generates unnecessary objects, which can affect production performance due to additional GC load.
BrandonShar
reviewed
Oct 25, 2024
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Thanks for the PR @skryukov !
To make sure I understand, is this PR purely a performance optimization? It looks to me like the specs you added will pass with the existing logic, right?
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@BrandonShar Not quite - previously we passed the value from the request's |
BrandonShar
approved these changes
Oct 25, 2024
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Released in 3.3.0! |
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The Vary header is a way for servers to control caching mechanisms, and it is purely a server-side mechanism. The client does not control or affect the Vary header. Issue #136 introduced logic that does not conform to this: https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-semantics-19#section-12.5.5
There are several approaches we can take with the Vary header:
Vary: X-Inertiaheader.Varyheader if it wasn't set before, which is the default logic used in Rails: https://github.com/rails/rails/blob/b8720e7cb8c9894d142b8576c21065c92cd1907a/actionpack/lib/action_controller/metal/rendering.rb#L220-L224X-Inertiaif theVaryheader was set previously, or set theVary: X-Inertiaheader if it was not.I believe the third option makes the most sense: it allows users to add other headers, like
Accept-Language, to theVarylist, but it also prevents them from omittingX-Inertia.