Merge pull request #34491 from rails/fix-query-cache-on-multiple-connections

Fix query cache for multiple connections

activerecord/lib/active_record/query_cache.rb

@@ -26,17 +26,24 @@ def uncached(&block)
     end
 
     def self.run
-      ActiveRecord::Base.connection_handler.connection_pool_list.
-        reject { |p| p.query_cache_enabled }.each { |p| p.enable_query_cache! }
+      pools = []
+
+      ActiveRecord::Base.connection_handlers.each do |key, handler|
+        pools << handler.connection_pool_list.reject { |p| p.query_cache_enabled }.each { |p| p.enable_query_cache! }
+      end
+
+      pools.flatten
     end
 
     def self.complete(pools)
       pools.each { |pool| pool.disable_query_cache! }
 
-      ActiveRecord::Base.connection_handler.connection_pool_list.each do |pool|
+      ActiveRecord::Base.connection_handlers.each do |_, handler|
+        handler.connection_pool_list.each do |pool|
           pool.release_connection if pool.active_connection? && !pool.connection.transaction_open?
         end
       end
+    end
 
     def self.install_executor_hooks(executor = ActiveSupport::Executor)
       executor.register_hook(self)

activerecord/test/cases/query_cache_test.rb

@@ -55,6 +55,22 @@ def test_exceptional_middleware_clears_and_disables_cache_on_error
     assert_cache :off
   end
 
+  def test_query_cache_is_applied_to_connections_in_all_handlers
+    ActiveRecord::Base.connected_to(role: :reading) do
+      ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations["arunit"])
+    end
+
+    mw = middleware { |env|
+      ro_conn = ActiveRecord::Base.connection_handlers[:reading].connection_pool_list.first.connection
+      assert_predicate ActiveRecord::Base.connection, :query_cache_enabled
+      assert_predicate ro_conn, :query_cache_enabled
+    }
+
+    mw.call({})
+  ensure
+    ActiveRecord::Base.connection_handlers = { writing: ActiveRecord::Base.default_connection_handler }
+  end
+
   def test_query_cache_across_threads
     with_temporary_connection_pool do
       begin