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 7cbf01ec6511f1beeaefb0e47061826e005bdc22..06b9bc576514c8724ec0b60917f829d37360da81 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -334,7 +334,7 @@ def initialize(pools = Hash.new { |h,k| h[k] = {} })
       end
 
       def connection_pools
-        @connection_pools[$$]
+        @connection_pools[Process.pid]
       end
 
       def establish_connection(name, spec)
@@ -409,20 +409,20 @@ def retrieve_connection_pool(klass)
       private
 
       def class_to_pool
-        @class_to_pool[$$]
+        @class_to_pool[Process.pid]
       end
 
       def set_pool_for_spec(spec, pool)
-        @connection_pools[$$][spec] = pool
+        @connection_pools[Process.pid][spec] = pool
       end
 
       def set_class_to_pool(name, pool)
-        @class_to_pool[$$][name] = pool
+        @class_to_pool[Process.pid][name] = pool
         pool
       end
 
       def get_pool_for_class(klass)
-        @class_to_pool[$$].fetch(klass) {
+        @class_to_pool[Process.pid].fetch(klass) {
           c_to_p = @class_to_pool.values.find { |class_to_pool|
             class_to_pool[klass]
           }
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index 5905242747dea117f8d3c4ecccc6aba009d5cc8b..724dbff1f0740db49ad22cf6420e15653fc9e0fa 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -119,7 +119,7 @@ def clear
 
         private
         def cache
-          @cache[$$]
+          @cache[Process.pid]
         end
       end
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 7414d38aead1592543221233a7b50dcd678b5fed..d04f04b20179add4c09fe49a0f44ea931b9f1bd3 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -359,7 +359,7 @@ def delete(sql_key)
 
         private
         def cache
-          @cache[$$]
+          @cache[Process.pid]
         end
 
         def dealloc(key)