当前位置 博文首页 > .Net core 的热插拔机制的深入探索及卸载问题求救指南
依赖文件内容如下.一般位于编译生成目录中
{
"runtimeTarget": {
"name": ".NETCoreApp,Version=v3.1",
"signature": ""
},
"compilationOptions": {},
"targets": {
".NETCoreApp,Version=v3.1": {
"PluginSample/1.0.0": {
"dependencies": {
"Microsoft.Extensions.Hosting.Abstractions": "5.0.0-rc.2.20475.5"
},
"runtime": {
"PluginSample.dll": {}
}
},
"Microsoft.Extensions.Configuration.Abstractions/5.0.0-rc.2.20475.5": {
"dependencies": {
"Microsoft.Extensions.Primitives": "5.0.0-rc.2.20475.5"
},
"runtime": {
"lib/netstandard2.0/Microsoft.Extensions.Configuration.Abstractions.dll": {
"assemblyVersion": "5.0.0.0",
"fileVersion": "5.0.20.47505"
}
}
...
使用DependencyContextJsonReader加载依赖配置文件源码查看
using (var dependencyFileStream = File.OpenRead("Sample.deps.json"))
{
using (DependencyContextJsonReader dependencyContextJsonReader = new DependencyContextJsonReader())
{
//得到对应的实体文件
var dependencyContext =
dependencyContextJsonReader.Read(dependencyFileStream);
//定义的运行环境,没有,则为全平台运行.
string currentRuntimeIdentifier= dependencyContext.Target.Runtime;
//运行时所需要的dll文件
var assemblyNames= dependencyContext.RuntimeLibraries;
}
}
安装 Microsoft.NETCore.Platforms包,并找到runtime.json运行时定义文件.
{
"runtimes": {
"win-arm64": {
"#import": [
"win"
]
},
"win-arm64-aot": {
"#import": [
"win-aot",
"win-arm64"
]
},
"win-x64": {
"#import": [
"win"
]
},
"win-x64-aot": {
"#import": [
"win-aot",
"win-x64"
]
},
}
NET Core RID依赖关系示意图
win7-x64 win7-x86 | \ / | | win7 | | | | win-x64 | win-x86 \ | / win | any
.Net core常用发布平台RID如下
win-x64
win-x32
win-arm
osx-x64
linux-x64
linux-arm
1. .net core的runtime.json文件由微软提供:查看runtime.json.
2. runtime.json的runeims节点下,定义了所有的RID字典表以及RID树关系.
3. 根据*.deps.json依赖文件中的程序集定义RID标识,就可以判断出依赖文件中指向的dll是否能在某一平台运行.
4. 当程序发布为兼容模式时,我们出可以使用runtime.json文件选择性的加载平台dll并运行.
public class PluginLoadContext : AssemblyLoadContext
{
private AssemblyDependencyResolver _resolver;
public PluginLoadContext(string pluginFolder, params string[] commonAssemblyFolders) : base(isCollectible: true)
{
this.ResolvingUnmanagedDll += PluginLoadContext_ResolvingUnmanagedDll;
this.Resolving += PluginLoadContext_Resolving;
//第1步,解析des.json文件,并调用Load和LoadUnmanagedDll函数
_resolver = new AssemblyDependencyResolver(pluginFolder);
//第6步,通过第4,5步,解析仍失败的dll会自动尝试调用主程序中的程序集,
//如果失败,则直接抛出程序集无法加载的错误
}
private Assembly PluginLoadContext_Resolving(AssemblyLoadContext assemblyLoadContext, AssemblyName assemblyName)
{
//第4步,Load函数加载程序集失败后,执行的事件
}
private IntPtr PluginLoadContext_ResolvingUnmanagedDll(Assembly assembly, string unmanagedDllName)
{
//第5步,LoadUnmanagedDll加载native dll失败后执行的事件
}
protected override Assembly Load(AssemblyName assemblyName)
{
//第2步,先执行程序集的加载函数
}
protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
{
//第3步,先执行的native dll加载逻辑
}
}
微软官方示例代码如下:示例具体内容
class PluginLoadContext : AssemblyLoadContext
{
private AssemblyDependencyResolver _resolver;
public PluginLoadContext(string pluginPath)
{
_resolver = new AssemblyDependencyResolver(pluginPath);
}
protected override Assembly Load(AssemblyName assemblyName)
{
string assemblyPath = _resolver.ResolveAssemblyToPath(assemblyName);
if (assemblyPath != null)
{
//加载程序集
return LoadFromAssemblyPath(assemblyPath);
}
//返回null,则直接加载主项目程序集
return null;
}
protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
{
string libraryPath = _resolver.ResolveUnmanagedDllToPath(unmanagedDllName);
if (libraryPath != null)
{
//加载native dll文件
return LoadUnmanagedDllFromPath(libraryPath);
}
//返回IntPtr.Zero,即null指针.将会加载主项中runtimes文件夹下的dll
return IntPtr.Zero;
}
}
1. 官方这个示例是有问题的.LoadFromAssemblyPath()函数有bug,
该函数并不会加载依赖的程序集.正确用法是LoadFormStream()
2. Load和LoadUnmanagedDll函数实际上是给开发者手动加载程序集使用的,
自动加载应放到Resolving和ResolvingUnmanagedDll事件中
原因是,这样的加载顺序不会导致项目的程序集覆盖插件的程序集,造成程序集加载失败.
3. 手动加载时可以根据deps.json文件定义的runtime加载当前平台下的unmanaged dll文件.
这些平台相关的dll文件,一般位于发布目录中的runtimes文件夹中.
当你调用AssemblyLoadContext.UnLoad()卸载完插件以为相关程序集已经释放,那你可能就错了.官方文档表明卸载执行失败会抛出InvalidOperationException,不允许卸载官方说明。
但实际测试中,卸载失败,但并未报错.
插件
namespace PluginSample
{
public class SimpleService
{
public void Run(string name)
{
Console.WriteLine($"Hello World!");
}
}
}
加载插件
namespace Test
{
public class PluginLoader
{
pubilc AssemblyLoadContext assemblyLoadContext;
public Assembly assembly;
public Type type;
public MethodInfo method;
public void Load()
{
assemblyLoadContext = new PluginLoadContext("插件文件夹");
assembly = alc.Load(new AssemblyName("PluginSample"));
type = assembly.GetType("PluginSample.SimpleService");
method=type.GetMethod()
}
}
}
1. 在主项目程序中.AssemblyLoadContext,Assembly,Type,MethodInfo等不能直接定义在任何类中.
否则在插件卸载时会失败.当时为了测试是否卸载成功,采用手动加载,执行,卸载了1000次,
发现内存一直上涨,则表示卸载失败.
2. 参照官方文档后了解了WeakReferece类.使用该类与AssemblyLoadContext关联,当手动GC清理时,
AssemblyLoadContext就会变为null值,如果没有变为null值则表示卸载失败.
3. 使用WeakReference关联AssemblyLoadContext并判断是否卸载成功
public void Load(out WeakReference weakReference)
{
var assemblyLoadContext = new PluginLoadContext("插件文件夹");
weakReference = new WeakReference(pluginLoadContext, true);
assemblyLoadContext.UnLoad();
}
public void Check()
{
WeakReference weakReference=null;
Load(out weakReference);
//一般第二次,IsAlive就会变为False,即AssemblyLoadContext卸载失败.
for (int i = 0; weakReference.IsAlive && (i < 10); i++)
{
GC.Collect();
GC.WaitForPendingFinalizers();
}
}
4. 为了解决以上问题.可以把需要的变量放到静态字典中.在Unload之前把对应的Key值删除掉,即可.
public class SimpleService
{
//同步执行,插件卸载成功
public void Run(string name)
{
Console.WriteLine($"Hello {name}!");
}
//异步执行,卸载成功
public Task RunAsync(string name)
{
Console.WriteLine($"Hello {name}!");
return Task.CompletedTask;
}
//异步执行,卸载成功
public Task RunTask(string name)
{
return Task.Run(() => {
Console.WriteLine($"Hello {name}!");
});
}
//异步执行,卸载成功
public Task RunWaitTask(string name)
{
return Task.Run( async ()=> {
while (true)
{
if (CancellationTokenSource.IsCancellationRequested)
{
break;
}
await Task.Delay(1000);
Console.WriteLine($"Hello {name}!");
}
});
}
//异步执行,卸载成功
public Task RunWaitTaskForCancel(string name, CancellationToken cancellation)
{
return Task.Run(async () => {
while (true)
{
if (cancellation.IsCancellationRequested)
{
break;
}
await Task.Delay(1000);
Console.WriteLine($"Hello {name}!");
}
});
}
//异步执行,卸载失败
public async Task RunWait(string name)
{
while (true)
{
if (CancellationTokenSource.IsCancellationRequested)
{
break;
}
await Task.Delay(1000);
Console.WriteLine($"Hello {name}!");
}
}
//异步执行,卸载失败
public Task RunWaitNewTask(string name)
{
return Task.Factory.StartNew(async ()=> {
while (true)
{
if (CancellationTokenSource.IsCancellationRequested)
{
break;
}
await Task.Delay(1000);
Console.WriteLine($"Hello {name}!");
}
},TaskCreationOptions.DenyChildAttach);
}
}
1. 以上测试可以看出,如果插件调用的是一个常规带wait的async异步函数,则插件一定会卸载失败.
原因推测是返回的结果是编译器自动生成的状态机实现的,而状态机是在插件中定义的.
2. 如果在插件中使用Task.Factory.StartNew函数也会调用失败,原因不明.
官方文档说和Task.Run函数是Task.Factory.StartNew的简单形式,只是参数不同.官方说明
按照官方提供的默认参数测试,卸载仍然失败.说明这两种方式实现底层应该是不同的.
NFinal2开源框架。https://git.oschina.net/LucasDot/NFinal2/tree/master
jsjbwy