Zookeeper基础教程（六）：.net core使用Zookeeper

　　Demo代码已提交到gitee，感兴趣的更有可以直接克隆使用，地址：https://gitee.com/shanfeng1000/dotnetcore-demo/tree/master/Zookeeper

　　.net core要使用Zookeeper，我们还是推荐使用ZooKeeperNetEx这个插件，先在nuget中搜索安装ZooKeeperNetEx，然后可以在Startup类中直接使用ZooKeeperNetEx连接Zookeeper获取数据，也可以使用前面章节中介绍的ZookeeperHelper辅助类来操作，本文也是以这个Zookeeper辅助类来作为工具，将Zookeeper作为一个配置源，从而将它集成到.net core的Configuration-option配置中。

　　博主使用的是.net core2.2的版本，不过对2.*和3.*区别不大。

　　首先贴出简单的项目文件结构：

　　其中，Configurations目录下的一系列Zookeeper开头的文件是集成Zookeeper所需的类，下面单独介绍，首先从我们前面的文章中得到ZookeeperHelper这个辅助类：Zookeeper基础教程（四）：C#连接使用Zookeeper

　　ZookeeperConfigurationExtensions是一个拓展类，最终使用的是这个类的拓展方法去集成Zookeeper到Configuration配置源中

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace AspNetCore.ZookeeperApi.Configurations
{
    public static class ZookeeperConfigurationExtensions
    {
        /// <summary>
        /// 添加Zookeeper配置
        /// </summary>
        /// <param name="builder"></param>
        /// <param name="zookeeperState"></param>
        public static IConfigurationBuilder AddZookeeper(this IConfigurationBuilder builder, Action<ZookeeperOptions> configure)
        {
            var options = new ZookeeperOptions();
            configure?.Invoke(options);
            return builder.AddZookeeper(options);
        }
        /// <summary>
        /// 添加Zookeeper配置
        /// </summary>
        /// <param name="builder"></param>
        /// <param name="zookeeperState"></param>
        public static IConfigurationBuilder AddZookeeper(this IConfigurationBuilder builder, ZookeeperOptions zookeeperOptions)
        {
            ZookeeperConfigurationSource zookeeperConfigurationSource = new ZookeeperConfigurationSource(zookeeperOptions);
            builder.Add(zookeeperConfigurationSource);
            return builder;
        }
        /// <summary>
        /// 添加Zookeeper配置
        /// </summary>
        /// <param name="builder"></param>
        /// <param name="zookeeperState"></param>
        /// <returns></returns>
        public static IHostBuilder UseZookeeper(this IHostBuilder builder, ZookeeperOptions zookeeperOptions)
        {
            return builder.ConfigureAppConfiguration((_, cbuilder) => cbuilder.AddZookeeper(zookeeperOptions));
        }
        /// <summary>
        /// 添加Zookeeper配置
        /// </summary>
        /// <param name="builder"></param>
        /// <param name="zookeeperState"></param>
        /// <returns></returns>
        public static IWebHostBuilder UseZookeeper(this IWebHostBuilder builder, ZookeeperOptions zookeeperOptions)
        {
            return builder.ConfigureAppConfiguration((_, cbuilder) => cbuilder.AddZookeeper(zookeeperOptions));
        }
    }
}

ZookeeperConfigurationExtensions

　　ZookeeperConfigurationProvider是Zookeeper集成的核心类，主要是保存Zookeeper读取下来的数据　　

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Primitives;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace AspNetCore.ZookeeperApi.Configurations
{
    public class ZookeeperConfigurationProvider : ConfigurationProvider, IDisposable
    {
        ConfigurationReloadToken _reloadToken = new ConfigurationReloadToken();
        IDisposable _changeTokenRegistration;

        /// <summary>
        /// 监控对象
        /// </summary>
        ZookeeperConfigurationWatcher zookeeperConfigurationWatcher;
        public ZookeeperConfigurationSource ZookeeperConfigurationSource { get;private set; }

        public ZookeeperConfigurationProvider(ZookeeperConfigurationSource zookeeperConfigurationSource)
        {
            this.ZookeeperConfigurationSource = zookeeperConfigurationSource;
            this.zookeeperConfigurationWatcher = new ZookeeperConfigurationWatcher(this);

            if (zookeeperConfigurationSource.ZookeeperOptions.ReloadOnChange)
            {
                _changeTokenRegistration = ChangeToken.OnChange(
                    () => GetToken(),
                    () =>
                    {
                        Thread.Sleep(zookeeperConfigurationSource.ZookeeperOptions.ReloadDelay);
                        Load();
                    });
            }
        }

        /// <summary>
        /// 加载配置
        /// </summary>
        public override void Load()
        {
            Data = zookeeperConfigurationWatcher.Process();
        }
        /// <summary>
        /// 获取Token
        /// </summary>
        /// <returns></returns>
        private IChangeToken GetToken()
        {
            return _reloadToken;
        }
        /// <summary>
        /// 重置
        /// </summary>
        public void Reload()
        {
            var previousToken = Interlocked.Exchange(ref _reloadToken, new ConfigurationReloadToken());
            previousToken.OnReload();//如果使用Onreload将会出问题，执行时间会越来越长，原因未找到
        }
        /// <summary>
        /// 释放
        /// </summary>
        public void Dispose()
        {
            _changeTokenRegistration?.Dispose();
        }
    }
}

ZookeeperConfigurationProvider

　　ZookeeperConfigurationSource类表示一个配置源　　

using Microsoft.Extensions.Configuration;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace AspNetCore.ZookeeperApi.Configurations
{
    public class ZookeeperConfigurationSource : IConfigurationSource
    {
        /// <summary>
        /// 源状态信息
        /// </summary>
        public ZookeeperOptions ZookeeperOptions { get; private set; }

        public ZookeeperConfigurationSource(ZookeeperOptions zookeeperOptions)
        {
            this.ZookeeperOptions = zookeeperOptions;
        }

        /// <summary>
        /// 获取配置提供者
        /// </summary>
        /// <param name="builder"></param>
        /// <returns></returns>
        public IConfigurationProvider Build(IConfigurationBuilder builder)
        {
            return new ZookeeperConfigurationProvider(this);
        }
    }
}

ZookeeperConfigurationSource

　　ZookeeperConfigurationWatcher是Zookeeper数据读取的核心类，ZookeeperHelper这个辅助类就是在这个类中连接Zookeeper去读取数据　　　　　

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace AspNetCore.ZookeeperApi.Configurations
{
    public class ZookeeperConfigurationWatcher : IDisposable
    {
        ZookeeperConfigurationProvider zookeeperConfigurationProvider;

        /// <summary>
        /// Zookeeper辅助操作类
        /// </summary>
        ZookeeperHelper zookeeperHelper;

        public ZookeeperConfigurationWatcher(ZookeeperConfigurationProvider zookeeperConfigurationProvider)
        {
            this.zookeeperConfigurationProvider = zookeeperConfigurationProvider;
            var options = zookeeperConfigurationProvider.ZookeeperConfigurationSource.ZookeeperOptions;
            zookeeperHelper = new ZookeeperHelper(options.Address, options.RootPath);
            //初次连接后，立即
            zookeeperHelper.OnConnected += () =>
            {
                if (options.Scheme != AuthScheme.World)
                {
                    zookeeperHelper.Authorize(options.Scheme, options.Auth);
                }
                zookeeperConfigurationProvider.Reload();
            };
            zookeeperHelper.Connect();
            int timeOut = 10;
            while (!zookeeperHelper.Connected && timeOut-- > 0)
            {
                Thread.Sleep(1000); //停一秒，等待连接完成
            }
            if (!zookeeperHelper.Connected)
            {
                throw new TimeoutException($"connect to zookeeper [{options.Address}] timeout");
            }

            if (options.ReloadOnChange)
            {
                //监听根节点下所有的znode节点，当任意节点发生改变后，即立刻重新加载
                zookeeperHelper.WatchAllAsync(ze =>
                {
                    if (ze.Type != ZookeeperEvent.EventType.None)
                    {
                        //使用一个异步去完成，同步会造成死锁
                        Task.Run(() =>
                        {
                            zookeeperConfigurationProvider.Reload();
                        });
                    }
                }).Wait();
            }
        }

        /// <summary>
        /// 获取Zookeeper中的数据
        /// </summary>
        /// <returns></returns>
        public IDictionary<string, string> Process()
        {
            return zookeeperHelper.GetDictionaryAsync().GetAwaiter().GetResult();
        }
        /// <summary>
        /// 声明状态已改变
        /// </summary>
        public void OnChange()
        {
            zookeeperConfigurationProvider.Reload();
        }
        /// <summary>
        /// 释放资源
        /// </summary>
        public virtual void Dispose()
        {
            zookeeperHelper.Dispose();
            zookeeperConfigurationProvider.Dispose();
        }
    }
}

ZookeeperConfigurationWatcher

　　ZookeeperOptions是相关配置信息　　

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace AspNetCore.ZookeeperApi.Configurations
{
    public class ZookeeperOptions
    {
        /// <summary>
        /// 是否监控源数据变化
        /// </summary>
        public bool ReloadOnChange { get; set; } = true;
        /// <summary>
        /// 加载延迟
        /// </summary>
        public int ReloadDelay { get; set; } = 250;
        /// <summary>
        /// Zookeeper集群地址
        /// </summary>
        public string[] Address { get; set; }
        /// <summary>
        /// Zookeeper初始路径
        /// </summary>
        public string RootPath { get; set; }
        /// <summary>
        /// 认证主题
        /// </summary>
        public AuthScheme Scheme { get; set; }
        /// <summary>
        /// 认证信息
        /// </summary>
        public string Auth { get; set; }
    }
}

ZookeeperOptions

　　然后是Program类：　　

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using AspNetCore.ZookeeperApi.Configurations;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

namespace AspNetCore.ZookeeperApi
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .UseZookeeper(new ZookeeperOptions()
                {
                    //Auth = "user:123",
                    //Scheme = AuthScheme.Digest,
                    //Address = new string[] { "192.168.209.133:2181", "192.168.209.134:2181", "192.168.209.135:2181" },
                    Address = new string[] { "192.168.209.133:2181" },
                    RootPath = "/Test"
                });
    }
}

　　其中UseZookeeper方法就是ZookeeperConfigurationExtensions的一个拓展方法，调用这个拓展方法之后，Zookeeper读取的配置可以通过IConfiguration这个服务对象读取了。

　　UseZookeeper拓展方法传入了一个参数，Address是Zookeeper连接地址，RootPath是项目配置在Zookeeper中的根节点路径。

　　假如我们在Zookeeper中创建一个znode节点：/Test，然后在/Test节点下创建5个子节点：/Test/Value1、/Test/Value2、/Test/Value3、/Test/Value4、/Test/Value5

　　然后分别将数据保存到这5个节点中：　　

   # Value1表示字符串类型数据 
　　set /Test/Value1 'this is string values'
　　# Value2表示整形类型数据
　　set /Test/Value2 1
　　# Value3表示浮点型数据
　　set /Test/Value3 3.14
　　# Value4表示布尔类型数据
　　set /Test/Value4 false
　　# Value5表示日期类型数据
　　set /Test/Value5 '2020-06-02'

　　上面说了，Zookeeper读取的配置可以通过IConfiguration这个服务对象读取，IConfiguration是.net core提供的配置服务，我们可以直接使用读取，但是推荐使用Option方式读取，比如为读取/Test节点下的5个节点数据，我们可以创建一个TestOptions类：　　

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace AspNetCore.ZookeeperApi
{
    public class TestOptions
    {
        /// <summary>
        /// 字符数据
        /// </summary>
        public string Value1 { get; set; }
        /// <summary>
        /// 整形数据
        /// </summary>
        public int Value2 { get; set; }
        /// <summary>
        /// 浮点型数据
        /// </summary>
        public decimal Value3 { get; set; }
        /// <summary>
        /// 布尔型数据
        /// </summary>
        public bool Value4 { get; set; }
        /// <summary>
        /// 日期数据
        /// </summary>
        public DateTime Value5 { get; set; }
    }
}

　　然后在Startup的ConfigureServices方法中注册　　

   public void ConfigureServices(IServiceCollection services)
   {
       services.Configure<TestOptions>(Configuration.GetSection("Test"));

       services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
   }

　　之后我们就可以直接使用Option注入的形式去访问了，比如我们创建一个TestController的控制器：　　

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;
using Microsoft.Extensions.DependencyInjection;

namespace AspNetCore.ZookeeperApi.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class TestController : ControllerBase
    {
        /// <summary>
        /// 输出
        /// </summary>
        /// <returns></returns>
        public TestOptions Get()
        {
            //这里不要使用IOptionsMonitor<>，IOption<>等，因为IOptions<>不能改变数据，而IOptionsMonitor<>有缓存IOptionsMonitorCache<>
            //推荐使用IOptionsSnapshot<>
            var options = HttpContext.RequestServices.GetService<IOptionsSnapshot<TestOptions>>();
            return options.Get("");
        }
    }
}

　　然后运行项目，访问http://localhost:5000/api/test就能得到：

　　可以看到Zookeeper中的数据成功被读取到，现在我们可以修改Zookeeper中/Test节点下的任意节点数据，如：　　

    set /Test/Value2 2

　　由于Zookeeper的监听机制，刷新页面，你会看到Value2的值也成功刷新了

　　注意：上面的TestController中使用的是如下代码获取Option

　　var options = HttpContext.RequestServices.GetService<IOptionsSnapshot<TestOptions>>();

　　使用的IOptionsSnapshot<>，但是使用IOptionsMonitor<>，IOptions<>等可以的得到Zookeeper的数据，但是因为IOptions<>不能改变数据，而IOptionsMonitor<>有缓存IOptionsMonitorCache<>，因此当修改Zookeeper数据更新后，虽然程序会重新从Zookeeper中获取数据，但是获取的Option是不会被更新的，也就是说，如果使用下面两个方法获取Option，option的值是不会更新的，当然，如果使用IOptionsMonitor<>读取前，先清理IOptionsMonitorCache<>缓存，也是可以正确读取到更新的

　　var options = HttpContext.RequestServices.GetService<IOptionsMonitor<TestOptions>>();

　　var options = HttpContext.RequestServices.GetService<IOptions<TestOptions>>();

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原文地址：https://www.cnblogs.com/shanfeng1000/p/12718304.html