pythonnet/src/embed_tests/TestDomainReload.cs at net8.0 · pythonnet/pythonnet · GitHub

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using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Reflection;

using System.Runtime.InteropServices;

using NUnit.Framework;

using Python.Runtime;

using PyRuntime = Python.Runtime.Runtime;

// This test case is disabled on .NET Standard because it doesn't have all the

// APIs we use. We could work around that, but .NET Core doesn't implement

// domain creation, so it's not worth it.

// Unfortunately this means no continuous integration testing for this case.

#if NETFRAMEWORK

namespace Python.EmbeddingTest

{

class TestDomainReload

{

abstract class CrossCaller : MarshalByRefObject

{

public abstract ValueType Execute(ValueType arg);

}

/// <summary>

/// Test that the python runtime can survive a C# domain reload without crashing.

///

/// At the time this test was written, there was a very annoying

/// seemingly random crash bug when integrating pythonnet into Unity.

///

/// The repro steps that David Lassonde, Viktoria Kovecses and

/// Benoit Hudson eventually worked out:

/// 1. Write a HelloWorld.cs script that uses Python.Runtime to access

/// some C# data from python: C# calls python, which calls C#.

/// 2. Execute the script (e.g. make it a MenuItem and click it).

/// 3. Touch HelloWorld.cs on disk, forcing Unity to recompile scripts.

/// 4. Wait several seconds for Unity to be done recompiling and

/// reloading the C# domain.

/// 5. Make python run the gc (e.g. by calling gc.collect()).

///

/// The reason:

/// A. In step 2, Python.Runtime registers a bunch of new types with

/// their tp_traverse slot pointing to managed code, and allocates

/// some objects of those types.

/// B. In step 4, Unity unloads the C# domain. That frees the managed

/// code. But at the time of the crash investigation, pythonnet

/// leaked the python side of the objects allocated in step 1.

/// C. In step 5, python sees some pythonnet objects in its gc list of

/// potentially-leaked objects. It calls tp_traverse on those objects.

/// But tp_traverse was freed in step 3 => CRASH.

///

/// This test distills what's going on without needing Unity around (we'd see

/// similar behaviour if we were using pythonnet on a .NET web server that did

/// a hot reload).

/// </summary>

[Test]

public static void DomainReloadAndGC()

{

Assert.IsFalse(PythonEngine.IsInitialized);

RunAssemblyAndUnload("test1");

Assert.That(PyRuntime.Py_IsInitialized() != 0,

"On soft-shutdown mode, Python runtime should still running");

RunAssemblyAndUnload("test2");

Assert.That(PyRuntime.Py_IsInitialized() != 0,

"On soft-shutdown mode, Python runtime should still running");

}

#region CrossDomainObject

class CrossDomainObjectStep1 : CrossCaller

{

public override ValueType Execute(ValueType arg)

{

try

{

// Create a C# user-defined object in Python. Asssing some values.

Type type = typeof(Python.EmbeddingTest.Domain.MyClass);

string code = string.Format(@"

import clr

clr.AddReference('{0}')

from Python.EmbeddingTest.Domain import MyClass

obj = MyClass()

obj.Method()

obj.StaticMethod()

obj.Property = 1

obj.Field = 10

", Assembly.GetExecutingAssembly().FullName);

using (Py.GIL())

using (var scope = Py.CreateScope())

{

scope.Exec(code);

using (PyObject obj = scope.Get("obj"))

{

Debug.Assert(obj.AsManagedObject(type).GetType() == type);

// We only needs its Python handle

return new NewReference(obj).DangerousMoveToPointer();

}

catch (Exception e)

{

Debug.WriteLine(e);

throw;

}

class CrossDomainObjectStep2 : CrossCaller

{

public override ValueType Execute(ValueType arg)

{

// handle refering a clr object created in previous domain,

// it should had been deserialized and became callable agian.

using var handle = NewReference.DangerousFromPointer((IntPtr)arg);

try

{

using (Py.GIL())

{

BorrowedReference tp = Runtime.Runtime.PyObject_TYPE(handle.Borrow());

IntPtr tp_clear = Util.ReadIntPtr(tp, TypeOffset.tp_clear);

Assert.That(tp_clear, Is.Not.Null);

using (PyObject obj = new PyObject(handle.Steal()))

{

obj.InvokeMethod("Method");

obj.InvokeMethod("StaticMethod");

using (var scope = Py.CreateScope())

{

scope.Set("obj", obj);

scope.Exec(@"

obj.Method()

obj.StaticMethod()

obj.Property += 1

obj.Field += 10

");

}

var clrObj = obj.As<Domain.MyClass>();

Assert.AreEqual(clrObj.Property, 2);

Assert.AreEqual(clrObj.Field, 20);

}

catch (Exception e)

{

Debug.WriteLine(e);

throw;

}

return 0;

}

/// <summary>

/// Create a C# custom object in a domain, in python code.

/// Unload the domain, create a new domain.

/// Make sure the C# custom object created in the previous domain has been re-created

/// </summary>

[Test]

public static void CrossDomainObject()

{

RunDomainReloadSteps<CrossDomainObjectStep1, CrossDomainObjectStep2>();

}

#endregion

/// <summary>

/// This is a magic incantation required to run code in an application

/// domain other than the current one.

/// </summary>

class Proxy : MarshalByRefObject

{

public void RunPython()

{

Console.WriteLine("[Proxy] Entering RunPython");

PythonRunner.RunPython();

Console.WriteLine("[Proxy] Leaving RunPython");

}

public object Call(string methodName, params object[] args)

{

var pythonrunner = typeof(PythonRunner);

var method = pythonrunner.GetMethod(methodName);

return method.Invoke(null, args);

}

static T CreateInstanceInstanceAndUnwrap<T>(AppDomain domain)

{

Type type = typeof(T);

var theProxy = (T)domain.CreateInstanceAndUnwrap(

type.Assembly.FullName,

type.FullName);

return theProxy;

}

/// <summary>

/// Create a domain, run the assembly in it (the RunPython function),

/// and unload the domain.

/// </summary>

static void RunAssemblyAndUnload(string domainName)

{

Console.WriteLine($"[Program.Main] === creating domain {domainName}");

AppDomain domain = CreateDomain(domainName);

// Create a Proxy object in the new domain, where we want the

// assembly (and Python .NET) to reside

var theProxy = CreateInstanceInstanceAndUnwrap<Proxy>(domain);

theProxy.Call(nameof(PythonRunner.InitPython), PyRuntime.PythonDLL);

// From now on use the Proxy to call into the new assembly

theProxy.RunPython();

theProxy.Call("ShutdownPython");

Console.WriteLine($"[Program.Main] Before Domain Unload on {domainName}");

AppDomain.Unload(domain);

Console.WriteLine($"[Program.Main] After Domain Unload on {domainName}");

// Validate that the assembly does not exist anymore

try

{

Console.WriteLine($"[Program.Main] The Proxy object is valid ({theProxy}). Unexpected domain unload behavior");

Assert.Fail($"{theProxy} should be invlaid now");

}

catch (AppDomainUnloadedException)

{

Console.WriteLine("[Program.Main] The Proxy object is not valid anymore, domain unload complete.");

}

private static AppDomain CreateDomain(string name)

{

// Create the domain. Make sure to set PrivateBinPath to a relative

// path from the CWD (namely, 'bin').

// See https://stackoverflow.com/questions/24760543/createinstanceandunwrap-in-another-domain

var currentDomain = AppDomain.CurrentDomain;

var domainsetup = new AppDomainSetup()

{

ApplicationBase = currentDomain.SetupInformation.ApplicationBase,

ConfigurationFile = currentDomain.SetupInformation.ConfigurationFile,

LoaderOptimization = LoaderOptimization.SingleDomain,

PrivateBinPath = "."

};

var domain = AppDomain.CreateDomain(

$"My Domain {name}",

currentDomain.Evidence,

domainsetup);

return domain;

}

/// <summary>

/// Resolves the assembly. Why doesn't this just work normally?

/// </summary>

static Assembly ResolveAssembly(object sender, ResolveEventArgs args)

{

var loadedAssemblies = AppDomain.CurrentDomain.GetAssemblies();

foreach (var assembly in loadedAssemblies)

{

if (assembly.FullName == args.Name)

{

return assembly;

}

return null;

}

static void RunDomainReloadSteps<T1, T2>() where T1 : CrossCaller where T2 : CrossCaller

{

ValueType arg = null;

Type type = typeof(Proxy);

{

AppDomain domain = CreateDomain("test_domain_reload_1");

try

{

var theProxy = CreateInstanceInstanceAndUnwrap<Proxy>(domain);

theProxy.Call(nameof(PythonRunner.InitPython), PyRuntime.PythonDLL);

var caller = CreateInstanceInstanceAndUnwrap<T1>(domain);

arg = caller.Execute(arg);

theProxy.Call("ShutdownPython");

}

finally

{

AppDomain.Unload(domain);

}

{

AppDomain domain = CreateDomain("test_domain_reload_2");

try

{

var theProxy = CreateInstanceInstanceAndUnwrap<Proxy>(domain);

theProxy.Call(nameof(PythonRunner.InitPython), PyRuntime.PythonDLL);

var caller = CreateInstanceInstanceAndUnwrap<T2>(domain);

caller.Execute(arg);

theProxy.Call("ShutdownPythonCompletely");

}

finally

{

AppDomain.Unload(domain);

}

Assert.IsTrue(PyRuntime.Py_IsInitialized() != 0);

}

// The code we'll test. All that really matters is

// using GIL { Python.Exec(pyScript); }

// but the rest is useful for debugging.

// What matters in the python code is gc.collect and clr.AddReference.

// Note that the language version is 2.0, so no $"foo{bar}" syntax.

static class PythonRunner

{

public static void RunPython()

{

AppDomain.CurrentDomain.DomainUnload += OnDomainUnload;

string name = AppDomain.CurrentDomain.FriendlyName;

Console.WriteLine("[{0} in .NET] In PythonRunner.RunPython", name);

using (Py.GIL())

{

try

{

var pyScript = string.Format("import clr\n"

+ "print('[{0} in python] imported clr')\n"

+ "clr.AddReference('System')\n"

+ "print('[{0} in python] allocated a clr object')\n"

+ "import gc\n"

+ "gc.collect()\n"

+ "print('[{0} in python] collected garbage')\n",

name);

PythonEngine.Exec(pyScript);

}

catch (Exception e)

{

Console.WriteLine(string.Format("[{0} in .NET] Caught exception: {1}", name, e));

throw;

}

private static IntPtr _state;

public static void InitPython(string dllName)

{

PyRuntime.PythonDLL = dllName;

PythonEngine.Initialize();

_state = PythonEngine.BeginAllowThreads();

}

public static void ShutdownPython()

{

PythonEngine.EndAllowThreads(_state);

PythonEngine.Shutdown();

}

public static void ShutdownPythonCompletely()

{

PythonEngine.EndAllowThreads(_state);

PythonEngine.Shutdown();

}

static void OnDomainUnload(object sender, EventArgs e)

{

Console.WriteLine(string.Format("[{0} in .NET] unloading", AppDomain.CurrentDomain.FriendlyName));

}

namespace Python.EmbeddingTest.Domain

{

[Serializable]

public class MyClass

{

public int Property { get; set; }

public int Field;

public void Method() { }

public static void StaticMethod() { }

}

#endif

pythonnet/src/embed_tests/TestDomainReload.cs at net8.0 · pythonnet/pythonnet · GitHub

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