Dynamically set allow_concurrency. Closes #4044.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3862 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Dynamically set allow_concurrency.  #4044 [Stefan Kaes]
+
 * Added Base#to_xml that'll turn the current record into a XML representation [DHH]. Example:
 
     topic.to_xml

activerecord/lib/active_record/base.rb

@@ -310,7 +310,7 @@ module ActiveRecord #:nodoc:
     # Determines whether or not to use a connection for each thread, or a single shared connection for all threads.
     # Defaults to false. Set to true if you're writing a threaded application.
     cattr_accessor :allow_concurrency
-    @@allow_concurrency = true
+    @@allow_concurrency = false
 
     # Determines whether to speed up access by generating optimized reader
     # methods to avoid expensive calls to method_missing when accessing
@@ -1140,15 +1140,22 @@ module ActiveRecord #:nodoc:
           end
         end
 
-        def scoped_methods
-          if allow_concurrency
-            Thread.current[:scoped_methods] ||= {}
-            Thread.current[:scoped_methods][self] ||= []
-          else
-            @scoped_methods ||= []
-          end
+        def thread_safe_scoped_methods #:nodoc:
+          scoped_methods = (Thread.current[:scoped_methods] ||= {})
+          scoped_methods[self] ||= []
         end
-
+        
+        def single_threaded_scoped_methods #:nodoc:
+          @scoped_methods ||= []
+        end
+        
+        # pick up the correct scoped_methods version from @@allow_concurrency
+        if @@allow_concurrency
+          alias_method :scoped_methods, :thread_safe_scoped_methods
+        else
+          alias_method :scoped_methods, :single_threaded_scoped_methods
+        end
+        
         def current_scoped_methods
           scoped_methods.last
         end

activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb

@@ -22,15 +22,35 @@ module ActiveRecord
 
     class << self
       # Retrieve the connection cache.
-      def active_connections
-        if @@allow_concurrency
-          @@active_connections[Thread.current.object_id] ||= {}
-        else
-          @@active_connections
-        end
+      def thread_safe_active_connections #:nodoc:
+        @@active_connections[Thread.current.object_id] ||= {}
       end
-
-      @active_connection_name = nil
+     
+      def single_threaded_active_connections #:nodoc:
+        @@active_connections
+      end
+     
+      # pick up the right active_connection method from @@allow_concurrency
+      if @@allow_concurrency
+        alias_method :active_connections, :thread_safe_active_connections
+      else
+        alias_method :active_connections, :single_threaded_active_connections
+      end
+     
+      # set concurrency support flag (not thread safe, like most of the methods in this file)
+      def allow_concurrency=(threaded)
+        logger.debug "allow_concurrency=#{threaded}" if logger
+        return if @@allow_concurrency == threaded
+        clear_all_cached_connections!
+        @@allow_concurrency = threaded
+        method_prefix = threaded ? "thread_safe" : "single_threaded"
+        sing = (class << self; self; end)
+        [:active_connections, :scoped_methods].each do |method|
+          sing.send(:alias_method, method, "#{method_prefix}_#{method}")
+        end
+        log_connections if logger
+      end
+      
       def active_connection_name
         @active_connection_name ||=
            if active_connections[name] || @@defined_connections[name]
@@ -62,15 +82,19 @@ module ActiveRecord
 
       # Clears the cache which maps classes to connections.
       def clear_active_connections!
-        clear_cache!(@@active_connections)
+        clear_cache!(@@active_connections) do |name, conn|
+          conn.disconnect!
+        end
       end
 
       # Verify active connections.
       def verify_active_connections!
-        remove_stale_cached_threads!(@@active_connections) do |name, conn|
-          conn.disconnect!
+        if @@allow_concurrency
+          remove_stale_cached_threads!(@@active_connections) do |name, conn|
+            conn.disconnect!
+          end
         end
-
+        
         active_connections.each_value do |connection|
           connection.verify!(@@verification_timeout)
         end
@@ -106,6 +130,18 @@ module ActiveRecord
             clear_cache!(cache, thread_id, &block)
           end
         end
+        
+        def clear_all_cached_connections!
+          if @@allow_concurrency
+            @@active_connections.each_value do |connection_hash_for_thread|
+              connection_hash_for_thread.each_value {|conn| conn.disconnect! }
+              connection_hash_for_thread.clear
+            end
+          else
+            @@active_connections.each_value {|conn| conn.disconnect! }
+          end
+          @@active_connections.clear          
+        end
     end
 
     # Returns the connection currently associated with the class. This can
@@ -167,14 +203,6 @@ module ActiveRecord
       end
     end
 
-    def self.active_connections #:nodoc:
-      if @@allow_concurrency
-        Thread.current['active_connections'] ||= {}
-      else
-        @@active_connections ||= {}
-      end
-    end
-
     # Locate the connection of the nearest super class. This can be an
     # active or defined connections: if it is the latter, it will be
     # opened and set as the active connection for the class it was defined

activerecord/test/method_scoping_test.rb

@@ -9,7 +9,7 @@ class MethodScopingTest < Test::Unit::TestCase
   
   def test_set_conditions
     Developer.with_scope(:find => { :conditions => 'just a test...' }) do
-      assert_equal 'just a test...', Thread.current[:scoped_methods][Developer][-1][:find][:conditions]
+      assert_equal 'just a test...', Developer.send(:current_scoped_methods)[:find][:conditions]
     end
   end
 
@@ -64,7 +64,7 @@ class MethodScopingTest < Test::Unit::TestCase
     new_comment = nil
 
     VerySpecialComment.with_scope(:create => { :post_id => 1 }) do
-      assert_equal({ :post_id => 1 }, Thread.current[:scoped_methods][VerySpecialComment][-1][:create])
+      assert_equal({ :post_id => 1 }, VerySpecialComment.send(:current_scoped_methods)[:create])
       new_comment = VerySpecialComment.create :body => "Wonderful world"
     end
 
@@ -123,7 +123,7 @@ class NestedScopingTest < Test::Unit::TestCase
     Developer.with_scope(:find => { :conditions => "name = 'David'" }) do
       Developer.with_exclusive_scope(:find => { :conditions => "name = 'Jamis'" }) do
         assert_equal({:find => { :conditions => "name = 'Jamis'" }}, Developer.instance_eval('current_scoped_methods'))
-        assert_equal({:find => { :conditions => "name = 'Jamis'" }}, Thread.current[:scoped_methods][Developer][-1])
+        assert_equal({:find => { :conditions => "name = 'Jamis'" }}, Developer.send(:scoped_methods)[-1])
       end
     end
   end

activerecord/test/threaded_connections_test.rb

@@ -9,6 +9,16 @@ class ThreadedConnectionsTest < Test::Unit::TestCase
   def setup
     @connection = ActiveRecord::Base.remove_connection
     @connections = []
+    @allow_concurrency = ActiveRecord::Base.allow_concurrency
+  end
+  
+  def teardown
+    # clear the connection cache
+    ActiveRecord::Base.send(:clear_all_cached_connections!)
+    # set allow_concurrency to saved value
+    ActiveRecord::Base.allow_concurrency = @allow_concurrency
+    # reestablish old connection
+    ActiveRecord::Base.establish_connection(@connection)
   end
   
   def gather_connections(use_threaded_connections)