Dynamically set allow_concurrency. Closes #4044.

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

2 files changed, 63 insertions, 28 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 70d88e561b..9e3c54c7d4 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/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
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb
index fe581a14b5..8b70b2f047 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb
+++ b/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
+      def thread_safe_active_connections #:nodoc:
+        @@active_connections[Thread.current.object_id] ||= {}
+      end
+     
+      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
-
-      @active_connection_name = nil
+      
       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