Feat: backend supports with cookies

src/invidious/config.cr

@@ -167,6 +167,9 @@ class Config
   # The max resolution the Instance can offer
   property max_dash_resolution : Int32?
 
+  # List of names of the backends
+  property backends : Array(String) = [] of String
+
   # Materialious redirects
   property materialious_domain : String?
 

src/invidious/routes/switch_backend.cr

@@ -0,0 +1,18 @@
+{% skip_file if flag?(:api_only) %}
+
+module Invidious::Routes::BackendSwitcher
+  def self.switch(env)
+    referer = get_referer(env)
+    backend_id = env.params.query["backend_id"]
+
+    # Checks if there is any alternative domain, like a second domain name,
+    # TOR or I2P address
+    if alt = CONFIG.alternative_domains.index(env.request.headers["Host"])
+      env.response.cookies["SERVER_ID"] = Invidious::User::Cookies.server_id(CONFIG.alternative_domains[alt], backend_id)
+    else
+      env.response.cookies["SERVER_ID"] = Invidious::User::Cookies.server_id(CONFIG.domain, backend_id)
+    end
+
+    env.redirect referer
+  end
+end

src/invidious/routing.cr

@@ -21,6 +21,7 @@ module Invidious::Routing
       get "/privacy", Routes::Misc, :privacy
       get "/licenses", Routes::Misc, :licenses
       get "/redirect", Routes::Misc, :cross_instance_redirect
+      get "/switchbackend", Routes::BackendSwitcher, :switch
 
       self.register_channel_routes
       self.register_watch_routes

src/invidious/user/cookies.cr

@@ -45,5 +45,18 @@ struct Invidious::User
         samesite: HTTP::Cookie::SameSite::Lax
       )
     end
+
+    # Server ID (SERVER_ID) cookie used for Sticky Sessions
+    # Parameter "domain" comes from the global config
+    def server_id(domain : String?, server_id) : HTTP::Cookie
+      return HTTP::Cookie.new(
+        name: "SERVER_ID",
+        domain: domain,
+        value: server_id,
+        secure: false,
+        http_only: true,
+        samesite: HTTP::Cookie::SameSite::Lax
+      )
+    end
   end
 end

src/invidious/views/template.ecr

@@ -104,6 +104,15 @@
 					</div>
 				</div>
 
+				<% if CONFIG.backends %>
+				<div class="h-box">
+					Change backend:
+					<% CONFIG.backends.each do | backend | %>
+						<a href="/switchbackend?backend_id=<%= backend %>">Backend<%= backend %></a>
+                    <% end %>
+				</div>
+				<% end %>
+
 				<% if CONFIG.banner %>
 					<div class="h-box">
 						<h3><%= CONFIG.banner %></h3>