[Ironpython-users] SerializationException from IronPython.Runtime.Types.PythonType

[Alan Macdonald]

Hello,

I am experiencing an exception when tracing and would appreciate some
guidance.

I am hosting IronPython 2.7.1 in a .Net 4 C# host.  The host creates a new
app domain to run IronPython scripts in.  At the moment due to some
security exceptions I've given the new app domain unrestricted permissions
(I will try and reduce this later).  When the python script is executed it
runs via an asynchronous delegate and when complete catches any exceptions
during the running of the script.  This was all working fine and if the
python script has an error in it then the exception is caught in the async
callback method.

However I have since added tracing via a call to
ScriptEngine.SetTrace(myDelegate) so I can allow stepping through the
script one line at a time (based on http://devhawk.net/tag/debugger/).
When the script has no errors it executes fine with tracing enabled or
disabled.  However if the script has an error in it and tracing is enabled
then trying to catch and format the exception in the async delegate
callback causes a SerializationException on
IronPython.Runtime.Types.PythonType.  When tracing is not enabled the
exception is caught and formatted successfully.

I tried to disable tracing in the catch block before formatting the
exception but this makes no difference.  I understand that this is related
to sending the exception information from one app domain to another but I'm
not sure what I can do to get round it and what extra information it is
trying to send when tracing is enabled.  My tracing delegate does nothing
with exceptions.

Code that creates the new app domain and starts the async call to execute
the method for the object in the new app domain:
public void Run()
        {
            if (newDomainInstance == null)
                NewAppDomain();

            Execute method = newDomainInstance.ExecuteCode;
            method.BeginInvoke(RunComplete, method);

        }


The async callback is the following code:

 private void RunComplete(IAsyncResult cookie)
        {
            Complete = true;

            Execute method = (Execute)cookie.AsyncState;


            try
            {
                method.EndInvoke(cookie);
                OnExecutionSuccess();
            }
            catch (AppDomainUnloadedException adue)
            {
                //Do nothing because we've deliberately pulled the app
domain out from under it.
            }
            catch (Exception ex)
            {
                engine.Value.SetTrace(null);
                String extractedMessage =
engine.Value.GetService<ExceptionOperations>().FormatException(ex);
                OnExecutionError(new Exception(extractedMessage));
            }

        }

The exception occurs on String extractedMessage =
engine.Value.GetService<ExceptionOperations>().FormatException(ex);

Exception stacktrace:
System.Runtime.Serialization.SerializationException was unhandled
  Message=Type 'IronPython.Runtime.Types.PythonType' in Assembly
'IronPython, Version=2.7.0.40, Culture=neutral,
PublicKeyToken=7f709c5b713576e1' is not marked as serializable.
  Source=mscorlib
  StackTrace:
    Server stack trace:
       at
System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers(RuntimeType
type)
       at
System.Runtime.Serialization.FormatterServices.GetSerializableMembers(Type
type, StreamingContext context)
       at
System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitMemberInfo()
       at
System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object
obj, ISurrogateSelector surrogateSelector, StreamingContext context,
SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter,
ObjectWriter objectWriter, SerializationBinder binder)
       at
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Write(WriteObjectInfo
objectInfo, NameInfo memberNameInfo, NameInfo typeNameInfo)
       at
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object
graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck)
       at
System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream
serializationStream, Object graph, Header[] headers, Boolean fCheck)
       at
System.Runtime.Remoting.Channels.CrossAppDomainSerializer.SerializeMessageParts(ArrayList
argsToSerialize)
       at
System.Runtime.Remoting.Messaging.SmuggledMethodReturnMessage..ctor(IMethodReturnMessage
mrm)
       at
System.Runtime.Remoting.Messaging.SmuggledMethodReturnMessage.SmuggleIfPossible(IMessage
msg)
       at
System.Runtime.Remoting.Channels.CrossAppDomainSink.DoDispatch(Byte[]
reqStmBuff, SmuggledMethodCallMessage smuggledMcm,
SmuggledMethodReturnMessage& smuggledMrm)
       at
System.Runtime.Remoting.Channels.CrossAppDomainSink.DoTransitionDispatchCallback(Object[]
args)
    Exception rethrown at [0]:
       at System.Threading.Thread.InternalCrossContextCallback(Context ctx,
IntPtr ctxID, Int32 appDomainID, InternalCrossContextDelegate ftnToCall,
Object[] args)
       at
System.Runtime.Remoting.Messaging.AsyncReplySink.SyncProcessMessage(IMessage
reqMsg)
       at
System.Runtime.Remoting.Channels.ADAsyncWorkItem.FinishAsyncWork(Object
stateIgnored)
       at
System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(Object
state)
       at System.Threading.ExecutionContext.Run(ExecutionContext
executionContext, ContextCallback callback, Object state, Boolean
ignoreSyncCtx)
       at
System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
       at System.Threading.ThreadPoolWorkQueue.Dispatch()
       at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
  InnerException:


Any help would be appreciated.  If it helps I can show more code or if
anything is unclear please let me know. I didn't want to make it too long
and include unneccessary details.

Thanks for your time.

Alan
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