我如何在插件之间进行通信？

Question

我有一个插件系统，我在其中使用 MarshalByRefObject 为每个插件创建隔离域，因此用户可以重新加载他们认为合适的新版本，而无需关闭主应用程序。

现在我需要允许插件查看当前有哪些插件运行，也许 start/stop 一个特定的插件。

我知道如何从包装器发出命令，例如下面的代码：

using System;
using System.Linq;
using System.Reflection;
using System.Security.Permissions;

namespace Wrapper
{
    public class RemoteLoader : MarshalByRefObject
    {
        private Assembly _pluginAassembly;
        private object _instance;
        private string _name;

        public RemoteLoader(string assemblyName)
        {
            _name = assemblyName;
            if (_pluginAassembly == null)
            {
                _pluginAassembly = AppDomain.CurrentDomain.Load(assemblyName);
            }

            // Required to identify the types when obfuscated
            Type[] types;
            try
            {
                types = _pluginAassembly.GetTypes();
            }
            catch (ReflectionTypeLoadException e)
            {
                types = e.Types.Where(t => t != null).ToArray();
            }

            var type = types.FirstOrDefault(type => type.GetInterface("IPlugin") != null);
            if (type != null && _instance == null)
            {
                _instance = Activator.CreateInstance(type, null, null);
            }
        }
    
        public void Start()
        {
            if (_instance == null)
            {
                return;
            }
            ((IPlugin)_instance).OnStart();
        }

        public void Stop()
        {
            if (_instance == null)
            {
                return;
            }
            ((IPlugin)_instance).OnStop(close);
        }
    }
}

那么我可以，例如：

var domain = AppDomain.CreateDomain(Name, null, AppSetup);
var assemblyPath = Assembly.GetExecutingAssembly().Location;
var loader = (RemoteLoader)Domain.CreateInstanceFromAndUnwrap(assemblyPath, typeof(RemoteLoader).FullName);
loader.Start();

当然以上只是恢复样本...

然后在我的包装器上我有如下方法：

bool Start(string name);
bool Stop(string name);

这基本上是一个包装器，用于从列表中发布特定插件的 Start/Stop 和一个用于跟踪运行插件的列表：

List<Plugin> Plugins

插件只是一个简单的class，包含Domain、RemoteLoader信息等

我不明白的是，如何从插件内部实现以下内容。能够：

查看运行插件列表
执行特定插件的启动或停止

或者如果 MarshalByRefObject 考虑到插件是隔离的，那么这甚至是可能的，否则我将不得不打开不同的通信路径来实现这一点？

为了赏金，我正在寻找上述内容的可验证工作示例...

Answer 1

您可以让插件请求其宿主执行这些操作。您可以将主机创建的 MarshalByRefObject 派生 class 的实例传递给 RemoteLoader。 RemoteLoader 然后可以使用该实例执行任何操作。

您还可以通过从主机向每个插件传递合适的 MarshalByRefObject 来使插件相互通信。不过，我建议通过主机路由所有操作，因为它是一个更简单的架构。

Answer 2

首先让我们定义几个接口：

// this is your host
public interface IHostController {
    // names of all loaded plugins
    string[] Plugins { get; }
    void StartPlugin(string name);
    void StopPlugin(string name);
}
public interface IPlugin {
    // with this method you will pass plugin a reference to host
    void Init(IHostController host);
    void Start();
    void Stop();                
}
// helper class to combine app domain and loader together
public class PluginInfo {
    public AppDomain Domain { get; set; }
    public RemoteLoader Loader { get; set; }
}

现在稍微重写了 RemoteLoader（对我来说没有用）：

public class RemoteLoader : MarshalByRefObject {
    private Assembly _pluginAassembly;
    private IPlugin _instance;
    private string _name;

    public void Init(IHostController host, string assemblyPath) {
        // note that you pass reference to controller here
        _name = Path.GetFileNameWithoutExtension(assemblyPath);
        if (_pluginAassembly == null) {
            _pluginAassembly = AppDomain.CurrentDomain.Load(File.ReadAllBytes(assemblyPath));
        }

        // Required to identify the types when obfuscated
        Type[] types;
        try {
            types = _pluginAassembly.GetTypes();
        }
        catch (ReflectionTypeLoadException e) {
            types = e.Types.Where(t => t != null).ToArray();
        }

        var type = types.FirstOrDefault(t => t.GetInterface("IPlugin") != null);
        if (type != null && _instance == null) {
            _instance = (IPlugin) Activator.CreateInstance(type, null, null);
            // propagate reference to controller futher
            _instance.Init(host);
        }
    }

    public string Name => _name;
    public bool IsStarted { get; private set; }

    public void Start() {
        if (_instance == null) {
            return;
        }
        _instance.Start();
        IsStarted = true;
    }

    public void Stop() {
        if (_instance == null) {
            return;
        }
        _instance.Stop();
        IsStarted = false;
    }
}

和主持人：

// note : inherits from MarshalByRefObject and implements interface
public class HostController : MarshalByRefObject, IHostController {        
    private readonly Dictionary<string, PluginInfo> _plugins = new Dictionary<string, PluginInfo>();

    public void ScanAssemblies(params string[] paths) {
        foreach (var path in paths) {
            var setup = new AppDomainSetup();                
            var domain = AppDomain.CreateDomain(Path.GetFileNameWithoutExtension(path), null, setup);
            var assemblyPath = Assembly.GetExecutingAssembly().Location;
            var loader = (RemoteLoader) domain.CreateInstanceFromAndUnwrap(assemblyPath, typeof (RemoteLoader).FullName);
            // you are passing "this" (which is IHostController) to your plugin here
            loader.Init(this, path);                          
            _plugins.Add(loader.Name, new PluginInfo {
                Domain = domain,
                Loader = loader
            });
        }
    }

    public string[] Plugins => _plugins.Keys.ToArray();

    public void StartPlugin(string name) {
        if (_plugins.ContainsKey(name)) {
            var p = _plugins[name].Loader;
            if (!p.IsStarted) {
                p.Start();
            }
        }
    }

    public void StopPlugin(string name) {
        if (_plugins.ContainsKey(name)) {
            var p = _plugins[name].Loader;
            if (p.IsStarted) {
                p.Stop();
            }
        }
    }
}

现在让我们创建两个不同的程序集。他们每个人只需要引用 interfaces IPlugin 和 IHostController。在第一个程序集中定义插件：

public class FirstPlugin : IPlugin {
    const string Name = "First Plugin";

    public void Init(IHostController host) {
        Console.WriteLine(Name + " initialized");
    }

    public void Start() {
        Console.WriteLine(Name + " started");
    }

    public void Stop() {
        Console.WriteLine(Name + " stopped");
    }
}

在第二个程序集中定义另一个插件：

public class FirstPlugin : IPlugin {
    const string Name = "Second Plugin";
    private Timer _timer;
    private IHostController _host;

    public void Init(IHostController host) {
        Console.WriteLine(Name + " initialized");
        _host = host;
    }

    public void Start() {
        Console.WriteLine(Name + " started");
        Console.WriteLine("Will try to restart first plugin every 5 seconds");
        _timer = new Timer(RestartFirst, null, 5000, 5000);
    }

    int _iteration = 0;
    private void RestartFirst(object state) {
        // here we talk with a host and request list of all plugins
        foreach (var plugin in _host.Plugins) {
            Console.WriteLine("Found plugin " + plugin);
        }
        if (_iteration%2 == 0) {
            Console.WriteLine("Trying to start first plugin");
            // start another plugin from inside this one
            _host.StartPlugin("Plugin1");
        }
        else {
            Console.WriteLine("Trying to stop first plugin");
            // stop another plugin from inside this one
            _host.StopPlugin("Plugin1");
        }
        _iteration++;
    }

    public void Stop() {
        Console.WriteLine(Name + " stopped");
        _timer?.Dispose();
        _timer = null;
    }
}

现在在托管所有插件的主 .exe 中：

static void Main(string[] args) {
    var host = new HostController();
    host.ScanAssemblies(@"path to your first Plugin1.dll", @"path to your second Plugin2.dll");                  
    host.StartPlugin("Plugin2");
    Console.ReadKey();
}

输出为：

First Plugin initialized
Second Plugin initialized
Second Plugin started
Will try to restart first plugin every 5 seconds
Found plugin Plugin1
Found plugin Plugin2
Trying to start first plugin
First Plugin started
Found plugin Plugin1
Found plugin Plugin1
Found plugin Plugin2
Trying to stop first plugin
Found plugin Plugin2
Trying to stop first plugin
First Plugin stopped
First Plugin stopped
Found plugin Plugin1
Found plugin Plugin2
Trying to stop first plugin

我如何在插件之间进行通信？

How can I communicate between plugins?

c#

marshalbyrefobject

为了赏金，我正在寻找上述内容的可验证工作示例...