Mailman 3 Re: [Python.NET] .NET 2 and hang with AcquireLock - Python.NET

6 Jun 2006

      Thanks for the info. Looking at this, an idea came to mind 
that might be worth looking into:

Is GenerateReport() called on a per-request basis as a web 
service? If so, you might try initializing the python engine 
once at startup rather than per-request. I'm actually not sure 
that reinitializing the engine in the same process will 
work in any reliable way (there are allegations on the 
python lists that this is a grey area in regard to the 
C python runtime). 

If nothing else, it could be causing two instances of Reporting
to try to initialize the engine at the same time. Since they 
are both essentially initializing a single C runtime, I could 
imagine the GIL getting balled up in that case pretty easily.

-Brian
...
-----Original Message-----
From: Matthew Pontefract [mailto:MP@credaris.com] 
Sent: Tuesday, June 06, 2006 11:37 AM
To: Brian Lloyd; pythondotnet@python.org
Subject: RE: [Python.NET] .NET 2 and hang with AcquireLock
Thanks for your reply Brian - I have been playing around with 
this a fair bit. I checked out the source code from 
Subversion; the revision from 2nd June built with no problems 
and so I now have a .NET 2 build which appears to work well 
from the console etc.
Using this from my C# web service exhibits the same behaviour 
as before however! The problem is really quite tricky because 
in fact it is wider than I previously suspected: the web 
service will successfully acquire the lock once or twice in a 
row, but will then hang at the AcquireLock call regardless of 
whether a Python exception had been raised in code or not.
I don't think any of the C# code would have been called again 
(and I kept tabs on calls to acquire and drop the lock), nor 
is there any re-entrant code.
This prompted me to change my approach to a rather more 
satisfactory one
anyway: I use ZSI to create a separate web service from 
python directly and call that web service from my C# app. I 
use PythonNet because I want to use business code available 
in .NET assemblies. Thanks to PythonNet it's been a breeze to 
use Python in what is otherwise a very C# environment - I'm 
really pleased.
Even though I've changed tack, when I have time I'll get a 
debugger onto the PythonNet code and try and trace this 
further - I'll post back if I get anywhere. It would be 
interesting to know if it's something peculiar to me!
For your information, as requested, the code where the 
problem occurred is as follows (it's all a touch noddy - 
various permutations of this were tried, so that's why the gs 
lock object rather bizarrely ended up static etc...):
public class Reporting
  {
      private static IntPtr gs;
      public static void GenerateReport(String report)
      {
      	if (!PythonEngine.IsInitialized)
      	{
      		PythonEngine.Initialize();
      		gs = PythonEngine.AcquireLock();
      		try
      		{
PythonEngine.RunSimpleString("import sys");
PythonEngine.RunSimpleString("sys.path.append('g:/pyccolo')");
PythonEngine.RunSimpleString("from report.server_init import *");
PythonEngine.RunSimpleString("print(sys.path)");
PythonEngine.RunSimpleString("o.flush()");
      		}
      		finally
      		{
      			PythonEngine.ReleaseLock(gs);
      		}
      	}
gs = PythonEngine.AcquireLock();
      	try
      	{
PythonEngine.RunSimpleString("runReport('"+report+"')");
PythonEngine.RunSimpleString("o.flush()");
      	}
      	finally
      	{
      		PythonEngine.ReleaseLock(gs);
      	}
      }	
  }
Regards
Matthew
-----Original Message-----
From: Brian Lloyd [mailto:Brian.Lloyd@revolution.com]
Sent: 06 June 2006 14:24
To: Matthew Pontefract; pythondotnet@python.org
Subject: RE: [Python.NET] .NET 2 and hang with AcquireLock
Hi Matthew -
This is a tough kind of problem to debug through email ;)
Is there any chance that the exceptions you raise cause any 
of your C# to be called again?
If not, if there is any way you can distill your code to a 
relatively small example that demonstrates the problem, send 
it to me and I'll take a look.
-Brian
...
-----Original Message-----
From: pythondotnet-bounces@python.org 
[mailto:pythondotnet-bounces@python.org] On Behalf Of Matthew 
Pontefract
Sent: Tuesday, June 06, 2006 6:08 AM
To: pythondotnet@python.org
Subject: [Python.NET] .NET 2 and hang with AcquireLock
Hello
I have a question pertaining to running Python NET under 
.NET version 
2 which, admittedly, is not the version for which the packages are 
built.
All works just fine - I am using the PythonEngine inside a web 
service, acquiring the GIL before operations, releasing it in a 
'finally' block afterwards. This is fine provided no python 
exceptions 
are raised in the Python code. Even though the GIL is 
released in the 
C#, a subsequent call to AcquireLock will hang as if 
waiting for it to 
be released. No calls to acquirelock have been made between 
the last 
call to release the GIL and the call that hangs.
Has anyone else had this problem?
I am using Python 2.4
Regards
Matthew
Dr Matthew Pontefract
Credaris Portfolio Management
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Re: [Python.NET] .NET 2 and hang with AcquireLock

Brian Lloyd

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