Support Rails 6 multiple database connections.

lib/activerecord-refresh_connection/active_record/connection_adapters/refresh_connection_management.rb

@@ -8,6 +8,7 @@ def initialize(app, options = {})
         @options = DEFAULT_OPTIONS.merge(options)
         @mutex = Mutex.new
 
+        resolve_clear_connections
         reset_remain_count
       end
 
@@ -30,6 +31,41 @@ def call(env)
       private
 
       def clear_connections
+        __send__(@clear_connections)
+      end
+
+      def resolve_clear_connections
+        ar_version = ActiveRecord.gem_version.to_s
+
+        @clear_connections =
+          if ar_version >= "6.1"
+            :clear_multi_db_connections
+          elsif ar_version >= "6.0"
+            :clear_legacy_compatible_connections
+          else
+            :clear_legacy_connections
+          end
+      end
+
+      def clear_multi_db_connections
+        if should_clear_all_connections?
+          ActiveRecord::Base.connection_handler.all_connection_pools.each(&:disconnect!)
+        else
+          ActiveRecord::Base.connection_handler.all_connection_pools.each do |pool|
+            pool.release_connection if pool.active_connection? && !pool.connection.transaction_open?
+          end
+        end
+      end
+
+      def clear_legacy_compatible_connections
+        if should_clear_all_connections?
+          ActiveRecord::Base.connection_handlers.each_value(&:clear_all_connections!)
+        else
+          ActiveRecord::Base.connection_handlers.each_value(&:clear_active_connections!)
+        end
+      end
+
+      def clear_legacy_connections
         if should_clear_all_connections?
           ActiveRecord::Base.clear_all_connections!
         else