Handle deadlock victim (1205) exceptions outside of a transactions by retrying the query.

Add SQLServerAdapter.retry_deadlock_victim option to disable this handling.

Author: jrafanie

lib/active_record/connection_adapters/sqlserver/errors.rb

@@ -3,6 +3,9 @@ module ActiveRecord
   class LostConnection < WrappedDatabaseException
   end
 
+  class DeadlockVictim < WrappedDatabaseException
+  end
+  
   module ConnectionAdapters
     module Sqlserver
       module Errors

lib/active_record/connection_adapters/sqlserver_adapter.rb

@@ -179,7 +179,7 @@ class SQLServerAdapter < AbstractAdapter
       attr_reader :database_version, :database_year, :spid
 
       cattr_accessor :native_text_database_type, :native_binary_database_type, :native_string_database_type,
-                     :log_info_schema_queries, :enable_default_unicode_types, :auto_connect,
+                     :log_info_schema_queries, :enable_default_unicode_types, :auto_connect, :retry_deadlock_victim,
                      :cs_equality_operator, :lowercase_schema_reflection, :auto_connect_duration
 
       self.enable_default_unicode_types = true
@@ -347,6 +347,11 @@ def auto_connect_duration
         @@auto_connect_duration ||= 10
       end
 
+      def retry_deadlock_victim
+        @@retry_deadlock_victim.is_a?(FalseClass) ? false : true
+      end
+      alias :retry_deadlock_victim? :retry_deadlock_victim
+      
       def native_string_database_type
         @@native_string_database_type || (enable_default_unicode_types ? 'nvarchar' : 'varchar') 
       end
@@ -381,6 +386,8 @@ def translate_exception(e, message)
           RecordNotUnique.new(message,e)
         when /conflicted with the foreign key constraint/i
           InvalidForeignKey.new(message,e)
+        when /has been chosen as the deadlock victim/i
+          DeadlockVictim.new(message,e)
         when *lost_connection_messages
           LostConnection.new(message,e)
         else
@@ -485,7 +492,10 @@ def with_auto_reconnect
         begin
           yield
         rescue Exception => e
-          retry if translate_exception(e,e.message).is_a?(LostConnection) && auto_reconnected?
+          case translate_exception(e,e.message)
+            when LostConnection; retry if auto_reconnected?
+            when DeadlockVictim; retry if retry_deadlock_victim? && self.open_transactions == 0
+          end
           raise
         end
       end

test/cases/connection_test_sqlserver.rb

@@ -101,6 +101,26 @@ def setup
       assert @connection.spid.nil?
     end
 
+    if connection_mode_dblib?
+      should 'handle deadlock victim exception (1205) outside a transaction by retrying the query' do
+        query = "SELECT 1 as [one]"
+        expected = @connection.execute(query)
+        
+        # Execute the query to get a handle of the expected result, which will
+        # be returned after a simulated deadlock victim (1205).
+        raw_conn = @connection.instance_variable_get(:@connection)
+        stubbed_handle = raw_conn.execute(query)
+        @connection.send(:finish_statement_handle, stubbed_handle)
+        raw_conn.stubs(:execute).raises(deadlock_victim_exception(query)).then.returns(stubbed_handle)
+        
+        result = nil
+        assert_nothing_raised do
+          result = @connection.execute(query)
+        end
+        assert_equal expected, result
+      end
+    end
+    
     should 'be able to disconnect and reconnect at will' do
       @connection.disconnect!
       assert !@connection.active?
@@ -197,6 +217,15 @@ def assert_all_odbc_statements_used_are_closed(&block)
     GC.enable
   end
 
+  def deadlock_victim_exception(sql)
+    require 'tiny_tds/error'
+    error = TinyTds::Error.new("Transaction (Process ID #{Process.pid}) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.: #{sql}")
+    error.severity = 13
+    error.db_error_number = 1205
+    error
+  end
+  
+
   def with_auto_connect(boolean)
     existing = ActiveRecord::ConnectionAdapters::SQLServerAdapter.auto_connect
     ActiveRecord::ConnectionAdapters::SQLServerAdapter.auto_connect = boolean