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EXPERIMENTAL: preconnect and dns-prefetch resource hints for CDN domains (#26215)

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Why this change?

In https://web.dev/articles/preconnect-and-dns-prefetch, it describes
how hinting to the browser to preconnect to domains which we will
eventually use the connection for can help improve the time it takes to
load a page.

We are putting this behind an experimental flag so that we can test and
profile this in a production environment.

What does this change introduce?

Introduce a hidden experimental `experimental_preconnect_link_header`
site setting which when enabled will add the `preconnect` and
`dns-prefetch` resource hints to the response headers for full page load
requests.
This commit is contained in:
Alan Guo Xiang Tan
2024-03-18 13:45:41 +08:00
committed by GitHub
parent d5b944f1de
commit 36cdb1444c
4 changed files with 58 additions and 8 deletions
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34
spec/requests/application_controller_spec.rb
View File

@ -1188,8 +1188,36 @@ RSpec.describe ApplicationController do
end
end
describe "preload Link header" do
context "with GlobalSetting.preload_link_header" do
describe "Link header" do
describe "when `experimental_preconnect_link_header` site setting is enabled" do
before { SiteSetting.experimental_preconnect_link_header = true }
it "should include the `preconnect` and `dns-prefetch` resource hints in the Link header when `GlobalSetting.cdn_url is configured`" do
global_setting :cdn_url, "https://cdn.example.com/something"
get "/latest"
expect(response.status).to eq(200)
expect(response.headers["Link"]).to include(
"<https://cdn.example.com>; rel=preconnect;, <https://cdn.example.com>; rel=dns-prefetch;",
)
end
it "should include the `preconnect` and `dns-prefetch` resource hints in the Link header when `SiteSetting.s3_cdn_url is configured`" do
SiteSetting.s3_cdn_url = "https://s3.some-cdn.com/something"
get "/latest"
expect(response.status).to eq(200)
expect(response.headers["Link"]).to include(
"<https://s3.some-cdn.com>; rel=preconnect;, <https://s3.some-cdn.com>; rel=dns-prefetch;",
)
end
end
context "when `GlobalSetting.preload_link_header` is enabled" do
before { global_setting :preload_link_header, true }
it "should have the Link header with assets on full page requests" do
@ -1203,7 +1231,7 @@ RSpec.describe ApplicationController do
end
end
context "without GlobalSetting.preload_link_header" do
context "when `GlobalSetting.preload_link_header` is disabled" do
before { global_setting :preload_link_header, false }
it "shouldn't have the Link header with assets on full page requests" do