From ab077d5787c3b80d3c8e35c9998847107ae03aa0 Mon Sep 17 00:00:00 2001
From: "Mark J. Titorenko" <mark@titorenko.net>
Date: Mon, 13 Jun 2011 02:14:18 +0100
Subject: [PATCH] use thread locals and an instance variable within
 QueryCache#BodyProxy to maintain appropriate linkage with AR database
 connection across threads

---
 .../connection_adapters/abstract/connection_pool.rb       | 2 +-
 .../abstract/connection_specification.rb                  | 8 ++++++++
 activerecord/lib/active_record/query_cache.rb             | 6 ++++--
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index 6f21cea2886ee..0541eedc26091 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -293,7 +293,7 @@ def new_connection
       end
 
       def current_connection_id #:nodoc:
-        Thread.current.object_id
+        ActiveRecord::Base.connection_id ||= Thread.current.object_id
       end
 
       def checkout_new_connection
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 bcd3abc08d575..cea81b48a5761 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb
@@ -89,6 +89,14 @@ def connection
         retrieve_connection
       end
 
+      def connection_id
+        Thread.current['ActiveRecord::Base.connection_id']
+      end
+
+      def connection_id=(connection_id)
+        Thread.current['ActiveRecord::Base.connection_id'] = connection_id
+      end
+
       # Returns the configuration of the associated connection as a hash:
       #
       #  ActiveRecord::Base.connection_config
diff --git a/activerecord/lib/active_record/query_cache.rb b/activerecord/lib/active_record/query_cache.rb
index 4e6167147334c..99b58e122b34c 100644
--- a/activerecord/lib/active_record/query_cache.rb
+++ b/activerecord/lib/active_record/query_cache.rb
@@ -28,9 +28,10 @@ def initialize(app)
     end
 
     class BodyProxy # :nodoc:
-      def initialize(original_cache_value, target)
+      def initialize(original_cache_value, target, connection_id)
         @original_cache_value = original_cache_value
         @target               = target
+        @connection_id        = connection_id
       end
 
       def each(&block)
@@ -40,6 +41,7 @@ def each(&block)
       def close
         @target.close if @target.respond_to?(:close)
       ensure
+        ActiveRecord::Base.connection_id = @connection_id
         ActiveRecord::Base.connection.clear_query_cache
         unless @original_cache_value
           ActiveRecord::Base.connection.disable_query_cache!
@@ -52,7 +54,7 @@ def call(env)
       ActiveRecord::Base.connection.enable_query_cache!
 
       status, headers, body = @app.call(env)
-      [status, headers, BodyProxy.new(old, body)]
+      [status, headers, BodyProxy.new(old, body, ActiveRecord::Base.connection_id)]
     end
   end
 end