Expose connections available in the connection pool.

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

@@ -56,7 +56,7 @@ module ActiveRecord
     # * +wait_timeout+: number of seconds to block and wait for a connection
     #   before giving up and raising a timeout error (default 5 seconds).
     class ConnectionPool
-      attr_reader :spec
+      attr_reader :spec, :connections
 
       # Creates a new ConnectionPool object. +spec+ is a ConnectionSpecification
       # object which describes database connection information (e.g. adapter,

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -579,6 +579,8 @@ module ActiveRecord
       protected
 
         def translate_exception(exception, message)
+          return super unless exception.respond_to?(:errno)
+
           case exception.errno
           when 1062
             RecordNotUnique.new(message, exception)

activerecord/test/cases/pooled_connections_test.rb

@@ -61,12 +61,14 @@ class PooledConnectionsTest < ActiveRecord::TestCase
     checkout_checkin_connections 1, 2
     assert_equal 2, @connection_count
     assert_equal 0, @timed_out
+    assert_equal 1, ActiveRecord::Base.connection_pool.connections.size
   end
 
   def test_pooled_connection_checkin_two
     checkout_checkin_connections 2, 3
     assert_equal 3, @connection_count
     assert_equal 0, @timed_out
+    assert_equal 1, ActiveRecord::Base.connection_pool.connections.size
   end
 
   def test_pooled_connection_checkout_existing_first