.NetCore的配置选项建议结合在一起学习,不了解.NetCore 配置Configuration的同学可以看下我的上一篇文章 [.Net Core配置Configuration源码研究]

由代码开始

定义一个用户配置选项

public class UserOptions
{
    private string instanceId;
    private static int index = 0;
    public UserOptions()
    {
        instanceId = (++index).ToString("00");
        Console.WriteLine($"Create UserOptions Instance:{instanceId}");
    }
    public string Name { get; set; }
    public int Age { get; set; }
    public override string ToString() => $"Name:{Name} Age:{Age} Instance:{instanceId} ";
}
public class UserOptions2
{
    public string Name { get; set; }
    public int Age { get; set; }
    public override string ToString() => $" Name:{Name} Age:{Age}";
}

定义json配置文件:myconfig.json

{
  "UserOption": {
    "Name": "ConfigName-zhangsan",
    "Age": 666
  }
}

创建ServiceCollection

services = new ServiceCollection();
var configBuilder = new ConfigurationBuilder().AddInMemoryCollection().AddJsonFile("myconfig.json", true, true);
var iconfiguration = configBuilder.Build();
services.AddSingleton<IConfiguration>(iconfiguration);

示例代码

services.Configure<UserOptions>(x => { x.Name = "张三"; x.Age = new Random().Next(1, 10000); });
services.AddOptions<UserOptions2>().Configure<IConfiguration>((x, config) => { x.Name = config["UserOption:Name"]; x.Age = 100; }); ;
services.PostConfigure<UserOptions>(x => { x.Name = x.Name + "Post"; x.Age = x.Age; });
services.Configure<UserOptions>("default", x => { x.Name = "Default-张三"; x.Age = new Random().Next(1, 10000); });
services.Configure<UserOptions>("config", configuration.GetSection("UserOption"));
using (var provider = services.BuildServiceProvider())
{
    using (var scope1 = provider.CreateScope())
    {
        PrintOptions(scope1, "Scope1");
    }

    //修改配置文件
    Console.WriteLine(string.Empty);
    Console.WriteLine("修改配置文件");
    var filePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "myconfig.json");
    File.WriteAllText(filePath, "{\"UserOption\": { \"Name\": \"ConfigName-lisi\", \"Age\": 777}}");
    //配置文件的change回调事件需要一定时间执行
    Thread.Sleep(300);
    Console.WriteLine(string.Empty);

    using (var scope2 = provider.CreateScope())
    {
        PrintOptions(scope2, "Scope2");
    }

    Console.WriteLine(string.Empty);

    using (var scope3 = provider.CreateScope())
    {
        PrintOptions(scope3, "Scope3");
    }
}

static void PrintOptions(IServiceScope scope, string scopeName)
{
    var options1 = scope.ServiceProvider.GetService<IOptions<UserOptions>>();
    Console.WriteLine($"手动注入读取,IOptions,{scopeName}-----{ options1.Value}");

    var options2 = scope.ServiceProvider.GetService<IOptionsSnapshot<UserOptions>>();
    Console.WriteLine($"配置文件读取,IOptionsSnapshot,{scopeName}-----{ options2.Value}");
    var options3 = scope.ServiceProvider.GetService<IOptionsSnapshot<UserOptions>>();
    Console.WriteLine($"配置文件根据名称读取,IOptionsSnapshot,{scopeName}-----{ options3.Get("config")}");

    var options4 = scope.ServiceProvider.GetService<IOptionsMonitor<UserOptions>>();
    Console.WriteLine($"配置文件读取,IOptionsMonitor,{scopeName}-----{ options4.CurrentValue}");
    var options5 = scope.ServiceProvider.GetService<IOptionsMonitor<UserOptions>>();
    Console.WriteLine($"配置文件根据名称读取,IOptionsMonitor,{scopeName}-----{options5.Get("config")}");

    var options6 = scope.ServiceProvider.GetService<IOptions<UserOptions2>>();
    Console.WriteLine($"Options2-----{options6.Value}");
}

代码运行结果

Create UserOptions Instance:01
手动注入读取,IOptions,Scope1----- Name:张三Post Age:6575 Instance:01
Create UserOptions Instance:02
配置文件读取,IOptionsSnapshot,Scope1----- Name:张三Post Age:835 Instance:02
Create UserOptions Instance:03
配置文件根据名称读取,IOptionsSnapshot,Scope1----- Name:ConfigName-zhangsan Age:666 Instance:03
Create UserOptions Instance:04
配置文件读取,IOptionsMonitor,Scope1----- Name:张三Post Age:1669 Instance:04
Create UserOptions Instance:05
配置文件根据名称读取,IOptionsMonitor,Scope1----- Name:ConfigName-zhangsan Age:666 Instance:05
Options2----- Name:ConfigName-zhangsan Age:100

修改配置文件
Create UserOptions Instance:06

手动注入读取,IOptions,Scope2----- Name:张三Post Age:6575 Instance:01
Create UserOptions Instance:07
配置文件读取,IOptionsSnapshot,Scope2----- Name:张三Post Age:5460 Instance:07
Create UserOptions Instance:08
配置文件根据名称读取,IOptionsSnapshot,Scope2----- Name:ConfigName-lisi Age:777 Instance:08
配置文件读取,IOptionsMonitor,Scope2----- Name:张三Post Age:1669 Instance:04
配置文件根据名称读取,IOptionsMonitor,Scope2----- Name:ConfigName-lisi Age:777 Instance:06
Options2----- Name:ConfigName-zhangsan Age:100

手动注入读取,IOptions,Scope3----- Name:张三Post Age:6575 Instance:01
Create UserOptions Instance:09
配置文件读取,IOptionsSnapshot,Scope3----- Name:张三Post Age:5038 Instance:09
Create UserOptions Instance:10
配置文件根据名称读取,IOptionsSnapshot,Scope3----- Name:ConfigName-lisi Age:777 Instance:10
配置文件读取,IOptionsMonitor,Scope3----- Name:张三Post Age:1669 Instance:04
配置文件根据名称读取,IOptionsMonitor,Scope3----- Name:ConfigName-lisi Age:777 Instance:06
Options2----- Name:ConfigName-zhangsan Age:100

通过运行代码得到的结论

  • Options可通过手动初始化配置项配置(可在配置时读取依赖注入的对象)、或通过IConfiguration绑定配置
  • PostConfiger可在Configer基础上继续配置
  • 可通过IOptionsSnapshot或IOptionsMonitor根据配置名称读取配置项,未指定名称读取第一个注入的配置
  • IOptions和IOptionsMonitor生命周期为Singleton,IOptionsSnapshot生命周期为Scope
  • IOptionsMonitor可监听到配置文件变动去动态更新配置项

问题

  • IOptions,IOptionsSnapshot,IOptionsMonitor 如何/何时注入、初始化
  • Options指定名称时内部是如何设置的
  • Options如何绑定的IConfiguration
  • IOptionsMonitor是如何同步配置文件变动的


配合源码解决疑惑

Configure注入

public static IServiceCollection Configure<TOptions>(this IServiceCollection services, Action<TOptions> configureOptions) where TOptions : class
{
    return services.Configure(Microsoft.Extensions.Options.Options.DefaultName, configureOptions);
}

public static IServiceCollection Configure<TOptions>(this IServiceCollection services, string name, Action<TOptions> configureOptions) where TOptions : class
{
	services.AddOptions();
	services.AddSingleton((IConfigureOptions<TOptions>)new ConfigureNamedOptions<TOptions>(name, configureOptions));
	return services;
}

public static IServiceCollection AddOptions(this IServiceCollection services)
{
	services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptions<>), typeof(OptionsManager<>)));
	services.TryAdd(ServiceDescriptor.Scoped(typeof(IOptionsSnapshot<>), typeof(OptionsManager<>)));
	services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitor<>), typeof(OptionsMonitor<>)));
	services.TryAdd(ServiceDescriptor.Transient(typeof(IOptionsFactory<>), typeof(OptionsFactory<>)));
	services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitorCache<>), typeof(OptionsCache<>)));
	return services;
}

通过上面的源码可以发现,Options相关类是在AddOptions中注入的,具体的配置项在Configure中注入。

如果不指定Configure的Name,也会有个默认的Name=Microsoft.Extensions.Options.Options.DefaultName

那么我们具体的配置项存到哪里去了呢,在ConfigureNamedOptions这个类中,在Configer函数调用时,只是把相关的配置委托存了起来:

public ConfigureNamedOptions(string name, Action<TOptions> action)
{
	Name = name;
	Action = action;
}

OptionsManager

private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(StringComparer.Ordinal);

public TOptions Value => Get(Options.DefaultName);

public virtual TOptions Get(string name)
{
	name = name ?? Options.DefaultName;
	return _cache.GetOrAdd(name, () => _factory.Create(name));
}

OptionsManager实现相对较简单,在查询时需要执行Name,如果为空就用默认的Name,如果缓存没有,就用Factory创建一个,否则就读缓存中的选项。

IOptionsIOptionsSnapshot的实现类都是OptionsManager,只是生命周期不同。


OptionsFactory

那么OptionsFactory又是如何创建Options的呢?我们看一下他的构造函数,构造函数将所有ConfigurePostConfigure的初始化委托都通过构造函数保存在内部变量中

public OptionsFactory(IEnumerable<IConfigureOptions<TOptions>> setups, IEnumerable<IPostConfigureOptions<TOptions>> postConfigures)
	{
        _setups = setups;
        _postConfigures = postConfigures;
	}

接下来看Create(有删改,与本次研究无关的代码没有贴出来):

	public TOptions Create(string name)
	{
        //首先创建对应Options的实例
		TOptions val = Activator.CreateInstance<TOptions>();
        //循环所有的配置项,依次执行,如果对同一个Options配置了多次,最后一次的赋值生效
		foreach (IConfigureOptions<TOptions> setup in _setups)
		{
			var configureNamedOptions = setup as IConfigureNamedOptions<TOptions>;
			if (configureNamedOptions != null)
			{
                //Configure中会判断传入Name的值与本身的Name值是否相同,不同则不执行Action
                //这解释了我们一开始的示例中,注入了三个UserOptions,但是在IOptionsSnapshot.Value中获取到的是第一个没有名字的
                //因为Value会调用OptionsManager.Get(Options.DefaultName),进而调用Factory的Create(Options.DefaultName)
				configureNamedOptions.Configure(name, val);
			}
			else if (name == Options.DefaultName)
			{
				setup.Configure(val);
			}
		}
        
        //PostConfigure没啥可多说了,名字判断逻辑与Configure一样
		foreach (var postConfigure in _postConfigures)
		{
			postConfigure.PostConfigure(name, val);
		}
		
		return val;
	}

NamedConfigureFromConfigurationOptions

IConfiguration配置Options的方式略有不同

对应Configure扩展方法最终调用的代码在Microsoft.Extensions.DependencyInjection.OptionsConfigurationServiceCollectionExtensions这个类中

public static IServiceCollection Configure<TOptions>(this IServiceCollection services, string name, IConfiguration config, Action<BinderOptions> configureBinder) where TOptions : class
{
	services.AddOptions();
	services.AddSingleton((IOptionsChangeTokenSource<TOptions>)new ConfigurationChangeTokenSource<TOptions>(name, config));
	return services.AddSingleton((IConfigureOptions<TOptions>)new NamedConfigureFromConfigurationOptions<TOptions>(name, config, configureBinder));
}

扩展方法里又注入了一个IOptionsChangeTokenSource,这个类的作用是提供一个配置文件变动监听的Token

同时将IConfigureOptions实现类注册成了NamedConfigureFromConfigurationOptions

NamedConfigureFromConfigurationOptions继承了ConfigureNamedOptions,在构造函数中用IConfiguration.Bind实现了生成Options的委托

	public NamedConfigureFromConfigurationOptions(string name, IConfiguration config, Action<BinderOptions> configureBinder)
		: base(name, (Action<TOptions>)delegate(TOptions options)
		{
			config.Bind(options, configureBinder);
		})

所以在Factory的Create函数中,会调用IConfigurationBind函数

由于IOptionsSnapshot生命周期是Scope,在配置文件变动后新的Scope中会获取最新的Options


ValidateOptions

OptionsBuilder还包含了一个Validate函数,该函数要求传入一个Func<TOptions,bool>的委托,会注入一个单例的ValidateOptions对象。

OptionsFactory构建Options的时候会验证Options的有效性,验证失败会抛出OptionsValidationException异常

对于ValidateOptionsPostConfigureOptions都是构建Options实例时需要用到的主要模块,不过使用和内部实现都较为简单,应用场景也不是很多,本文就不对这两个类多做介绍了


结论

Configure扩展函数中会首先调用AddOptions函数

IOptions,IOptionsSnapshot,IOptionsMonitor都是在AddOptions函数中注入的

Configure配置的选项配置委托最终会保存到ConfigureNamedOptionsNamedConfigureFromConfigurationOptions

IOptionsIOptionsSnapshot的实现类为OptionsManager

OptionsManager通过OptionsFactory创建Options的实例,并会以Name作为键存到字典中缓存实例

OptionsFactory会通过反射创建Options的实例,并调用ConfigureNamedOptions中的委托给实例赋值

现在只剩下最后一个问题了,OptionsMonitor是如何动态更新选项的呢?

其实前面的讲解中已经提到了一个关键的接口IOptionsChangeTokenSource,这个接口提供一个IChangeToken,通过ChangeToken监听这个Token就可以监听到文件的变动,我们来看下OptionsMonitor是否是这样做的吧!

//构造函数
public OptionsMonitor(IOptionsFactory<TOptions> factory, IEnumerable<IOptionsChangeTokenSource<TOptions>> sources, IOptionsMonitorCache<TOptions> cache)
{
    _factory = factory;
    _sources = sources;
    _cache = cache;
    //循环属于TOptions的所有IChangeToken
    foreach (IOptionsChangeTokenSource<TOptions> source in _sources)
    {
        ChangeToken.OnChange(() => source.GetChangeToken(), delegate(string name)
                             {

                                //清除缓存 
                                name = name ?? Options.DefaultName;
								_cache.TryRemove(name);
                             }, source.Name);
    }
}



public virtual TOptions Get(string name)
{
    name = name ?? Options.DefaultName;
    return _cache.GetOrAdd(name, () => _factory.Create(name));
}

果然是这样的吧!