.net core microservices 架构之 分布式

.net core microservices 架构之 分布式

 一：简介                                   

        自动计算都是常驻内存的，没有人机交互。我们经常用到的就是console job和sql job了。sqljob有自己的宿主，与数据库产品有很关联，暂时不提。console job使用quartz.net框架，目前3.x已经支持netcore。

        如果单台服务器运行计算，那就很简单了，quartz很强大了，而且支持故障灾难转移集群，docker做宿主，很容易实现。但是分布式就不可同日而语了。如果你的一个数据处理太慢，需要多进程多主机处理，那么就需要多进程自动协调处理这一数据，比如如果你的订单太多，而一个进程处理延迟是10秒，那用户体验就会非常不好，虽然异步已经提高了你的吞吐量，但是延迟太久，对后续业务还是造成很大的干扰，时不时的会进行停顿。如果两到三台的机器进行处理，那延迟就会大大的减低，但是这两到三台服务器如果分配处理任务？如何分割这个数据，多进程进行处理？就需要到这一篇讲解的知识了。

        在多个job应用之间进行协调的工具，就是zookeeper了，zookeeper官方介绍：一个分布式应用协调服务。其实他也是一个类似文件系统的写一致的数据存储软件，我们可以使用它做分布式锁，对应用进行协调控制。

       目前流行的这一类产品也比较多，但是我是熟悉quartz，至于切片的功能，在quartz之上可以进行封装，因为所要封装的功能不多，所以我还是选择了quartz。

二 zookeeper 服务                                                  

         首先就是zookeeper服务，和前面log日志一样，首先创建构建和配置文件类。

　　首先看看配置类：

ZookeeperConfiguration.cs

using Microsoft.Extensions.Configuration;

namespace Walt.Framework.Configuration
{
    public class ZookeeperConfiguration
    { 
        public IConfiguration Configuration { get; }

        public ZookeeperConfiguration(IConfiguration configuration)
        {
            Configuration = configuration;
        }
    }
    
}

ZookeeperConfigurationExtensioncs.cs

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Options;
using Walt.Framework.Service.Zookeeper;

namespace Walt.Framework.Configuration
{
    public static class ZookeeperConfigurationExtensioncs
    {
          public static IZookeeperBuilder AddConfiguration(this IZookeeperBuilder builder
          ,IConfiguration configuration)
          {
               
                InitService( builder,configuration); 
                return builder;
          }


          public static void InitService(IZookeeperBuilder builder,IConfiguration configuration)
          {
            builder.Services.TryAddSingleton<IConfigureOptions<ZookeeperOptions>>(
                  new ZookeeperConfigurationOptions(configuration));

            builder.Services.TryAddSingleton
            (ServiceDescriptor.Singleton<IOptionsChangeTokenSource<ZookeeperOptions>>(
                  new ConfigurationChangeTokenSource<ZookeeperOptions>(configuration)) );

            builder.Services
            .TryAddEnumerable(ServiceDescriptor.Singleton<IConfigureOptions<ZookeeperOptions>>
            (new ConfigureFromConfigurationOptions<ZookeeperOptions>(configuration)));
            
             builder.Services.AddSingleton(new ZookeeperConfiguration(configuration));
          }
    }
} 

ZookeeperConfigurationOptions.cs

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Options;
using Walt.Framework.Service.Zookeeper;

namespace Walt.Framework.Configuration
{
    public class ZookeeperConfigurationOptions : IConfigureOptions<ZookeeperOptions>
    {

        private readonly IConfiguration _configuration;


        public ZookeeperConfigurationOptions(IConfiguration configuration)
        {
           _configuration=configuration;
        }


        public void Configure(ZookeeperOptions options)
        {
             System.Diagnostics.Debug.WriteLine("zookeeper配置类，适配方法。"
             +Newtonsoft.Json.JsonConvert.SerializeObject(options));
        }
    }
}

以上这三个类就是配置类，下面是构建类和配置信息类：

ZookeeperBuilder.cs

using Microsoft.Extensions.DependencyInjection;

namespace Walt.Framework.Service.Zookeeper
{
    public class ZookeeperBuilder : IZookeeperBuilder
    {
        public IServiceCollection Services {get;}

        public ZookeeperBuilder(IServiceCollection services)
        {
            Services=services;
        }
    }
}

ZookeeperOptions.cs

using System;
using System.Collections.Generic;

namespace Walt.Framework.Service.Zookeeper
{
    public class ZookeeperOptions
    {
        /// <param name="connectstring">comma separated host:port pairs, each corresponding to a zk server. 
        /// e.g. "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002" If the optional chroot suffix is used the example would look like:
        /// "127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002/app/a" where the client would be rooted at "/app/a" and all paths would 
        /// be relative to this root - ie getting/setting/etc... "/foo/bar" would result in operations being run on "/app/a/foo/bar" 
        /// (from the server perspective).</param>
        public string Connectstring{get;set;}

        public int SessionTimeout{get;set;}
 
        public int SessionId{get;set;}

        public string SessionPwd{get;set;}

        public bool IsReadOnly{get;set;}

    }
}

ZookeeperService.cs 这个类中有两个watch类。

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using org.apache.zookeeper;
using org.apache.zookeeper.data;
using static org.apache.zookeeper.ZooKeeper;
using System.Linq;
using System.Linq.Expressions;
using System.Threading;
using static org.apache.zookeeper.Watcher.Event;
using Newtonsoft.Json;
using System.Collections.Concurrent;

namespace  Walt.Framework.Service.Zookeeper
{

    internal class  WaitLockWatch:Watcher
    {
        private AutoResetEvent _autoResetEvent;
        private ILogger _logger;

        private string _path;

        private ZookeeperService _zookeeperService;

        public string _tempNode;

        public WaitLockWatch(AutoResetEvent autoResetEvent
        ,ZookeeperService zookeeperService
        ,ILogger logger,string path
        ,string tempNode)
        {
            _autoResetEvent=autoResetEvent;
            _zookeeperService=zookeeperService;
            _logger=logger;
            _path=path;
            _tempNode=tempNode;
        }

       public override Task process(WatchedEvent @event)
       {
           _logger.LogDebug("{0}节点下子节点发生改变，激发监视方法。",_path);
            var childList=_zookeeperService.GetChildrenAsync(_path,null,true).Result;
            if(childList==null||childList.Children==null||childList.Children.Count<1)
                   {
                        _logger.LogDebug("获取子序列失败，计数为零.path:{0}",_path);
                        return Task.FromResult(0);
                   }
                   var top=childList.Children.OrderBy(or=>or).First();
                   if(_path+"/"+top==_tempNode)
                   {
                        _logger.LogDebug("释放阻塞");
                        _autoResetEvent.Set();
                   }
           
            return Task.FromResult(0);
       }
    }


    internal class WaitConnWatch : Watcher
    {
        private AutoResetEvent _autoResetEvent;
        private ILogger _logger;

        public WaitConnWatch(AutoResetEvent autoResetEvent
        ,ILogger logger)
        {
            _autoResetEvent=autoResetEvent;
            _logger=logger;
        }

       public override Task process(WatchedEvent @event)
       {
           _logger.LogDebug("watch激发,回掉状态：{0}",@event.getState().ToString());
            if(@event.getState()== KeeperState.SyncConnected
            ||@event.getState()== KeeperState.ConnectedReadOnly)
            {
                _logger.LogDebug("释放阻塞");
                _autoResetEvent.Set();
            }
            return Task.FromResult(0);
       }
    }

    public class ZookeeperService : IZookeeperService
    {

        public List<string> requestLockSequence=new List<string>();
        private object _lock=new object();
        private ZookeeperOptions _zookeeperOptions;
        private ZooKeeper _zookeeper;

         private static readonly byte[] NO_PASSWORD = new byte[0];

         public Watcher Wathcer {get;set;}

         public ILoggerFactory LoggerFac { get; set; }

         private ILogger _logger;

         AutoResetEvent[] autoResetEvent=new AutoResetEvent[2]
         {new AutoResetEvent(false),new AutoResetEvent(false)};

        public ZookeeperService(IOptionsMonitor<ZookeeperOptions>  zookeeperOptions
        ,ILoggerFactory loggerFac)
        {
            LoggerFac=loggerFac;
            _logger=LoggerFac.CreateLogger<ZookeeperService>();
            _zookeeperOptions=zookeeperOptions.CurrentValue; 
            _logger.LogDebug("配置参数：{0}",JsonConvert.SerializeObject(_zookeeperOptions));
             zookeeperOptions.OnChange((zookopt,s)=>{
                _zookeeperOptions=zookopt; 
            });
            _logger.LogDebug("开始连接");
            Conn(_zookeeperOptions); 
        }

       

        private void Conn(ZookeeperOptions zookeeperOptions)
        {
            bool isReadOnly=default(Boolean);
            Wathcer=new WaitConnWatch(autoResetEvent[0],_logger);
            if(isReadOnly!=zookeeperOptions.IsReadOnly)
            {
                isReadOnly=zookeeperOptions.IsReadOnly;
            }

            
            byte[] pwd=new byte[0];
            //如果没有密码和sessionId
            if(string.IsNullOrEmpty(zookeeperOptions.SessionPwd)
            &&_zookeeperOptions.SessionId==default(int))
            {
             _zookeeper=new ZooKeeper(zookeeperOptions.Connectstring,zookeeperOptions.SessionTimeout,Wathcer,isReadOnly);
            }
            else if (!string.IsNullOrEmpty(zookeeperOptions.SessionPwd))
            {
                pwd=System.Text.Encoding.Default.GetBytes(zookeeperOptions.SessionPwd);
                 _zookeeper=new ZooKeeper(zookeeperOptions.Connectstring,zookeeperOptions.SessionTimeout,Wathcer,0,pwd,isReadOnly);
            }
            else
            {
                 _zookeeper=new ZooKeeper(zookeeperOptions.Connectstring
                 ,zookeeperOptions.SessionTimeout,Wathcer,zookeeperOptions.SessionId,pwd,isReadOnly);
            }
             if(_zookeeper.getState()==States.CONNECTING)
            {
                _logger.LogDebug("当前状态：CONNECTING。阻塞等待");
                autoResetEvent[0].WaitOne();
            }
        }

        public Task<string> CreateZNode(string path,string data,CreateMode createMode,List<ACL> aclList)
        {
            ReConn();
            if(string.IsNullOrEmpty(path)||!path.StartsWith('/'))
            {
                _logger.LogDebug("path路径非法，参数：path：{0}",path);
                return null;
            }
            byte[] dat=new byte[0];
            if(string.IsNullOrEmpty(data))
            { 
                dat=System.Text.Encoding.Default.GetBytes(data);
            }
            if(createMode==null)
            {
                 _logger.LogDebug("createMode为null,默认使用CreateMode.PERSISTENT");
                createMode=CreateMode.PERSISTENT;
            }
            return _zookeeper.createAsync(path,dat,aclList,createMode);
        }

        public Task<DataResult> GetDataAsync(string path,Watcher watcher,bool isSync)
        {
            ReConn();
            if(_zookeeper.existsAsync(path).Result==null )
            {
                _logger.LogDebug("path不存在");
                return null;
            }
            if(isSync)
            {
                 _logger.LogDebug("即将进行同步。"); 
                 var task=Task.Run(async ()=>{
                    await _zookeeper.sync(path);  
                 }); 
                task.Wait();
            }
           

            return _zookeeper.getDataAsync(path,watcher);
        }

         public Task<Stat> SetDataAsync(string path,string data,bool isSync)
        {
            ReConn();
            if(_zookeeper.existsAsync(path).Result==null )
            {
                 _logger.LogDebug("path不存在");
                return null;
            }
            byte[] dat=new byte[0];
            if(!string.IsNullOrEmpty(data))
            { 
                dat=System.Text.Encoding.Default.GetBytes(data);
            }
            return _zookeeper.setDataAsync(path,dat);
        }

         public async Task<ChildrenResult> GetChildrenAsync(string path,Watcher watcher,bool isSync) 
         {
             ReConn();
              if(_zookeeper.existsAsync(path).Result==null )
            {
                 _logger.LogDebug("path不存在");
                return null;
            }
             if(isSync)
            {
                 _logger.LogDebug("即将进行同步。");
                 var task=Task.Run(async  ()=>{
                      _logger.LogDebug("开始同步");
                      await _zookeeper.sync(path);  
                 });
                task.Wait();
            }
             return await _zookeeper.getChildrenAsync(path,watcher);
         }

         public void DeleteNode(string path,String tempNode)
         {
             if(!string.IsNullOrEmpty(tempNode))
             {
                requestLockSequence.Remove(tempNode); 
             }
             ReConn();
              if(_zookeeper.existsAsync(path).Result==null )
            {
                 _logger.LogDebug("path不存在");
                return;
            }
            var  task=Task.Run(async ()=>{
                 _logger.LogDebug("删除node：{0}",path);
                  await _zookeeper.deleteAsync(path);
            });
            task.Wait();
            var sequencePath=requestLockSequence.Where(w=>path==w).FirstOrDefault();
            if(sequencePath!=null)
            {
                requestLockSequence.Remove(sequencePath);
            }
         }

         public  string GetDataByLockNode(string path,string sequenceName,List<ACL> aclList,out string tempNodeOut)
         {
             _logger.LogInformation("获取分布式锁开始。");
             ReConn();
             string tempNode=string.Empty;
             tempNodeOut=string.Empty;

              if(_zookeeper.existsAsync(path).Result==null )
            {
                 _logger.LogDebug("path不存在");
                return null;
            }

            
            try
            {
                _logger.LogDebug("开始锁定语句块");
                lock(_lock)
                {
                     _logger.LogDebug("锁定，访问requestLockSequence的代码应该同步。");
                    tempNode=requestLockSequence
                    .Where(w=>w.StartsWith(path+"/"+sequenceName)).FirstOrDefault();
                   
                    if(tempNode==null)
                    {
                        tempNode=CreateZNode(path+"/"+sequenceName,"",CreateMode.EPHEMERAL_SEQUENTIAL,aclList).Result;
                        _logger.LogDebug("创建节点：{0}",tempNode);
                        if(tempNode==null)
                        {
                            _logger.LogDebug("创建临时序列节点失败。详细参数:path:{0},data:{1},CreateMode:{2}"
                            ,path+"/squence","",CreateMode.EPHEMERAL_SEQUENTIAL);
                            return null;
                        }
                         _logger.LogInformation("创建成功，加入requestLockSequence列表。");
                        requestLockSequence.Add(tempNode);
                    }
                    else
                    {
                        _logger.LogDebug("已经存在的锁节点，返回null");
                        return null;
                    }
                }

                var childList= GetChildrenAsync(path,null,true).Result;
                   if(childList==null||childList.Children==null||childList.Children.Count<1)
                   {
                        _logger.LogDebug("获取子序列失败，计数为零.path:{0}",path);
                        return null;
                   }
                   _logger.LogDebug("获取path:{0}的子节点：{1}",path,Newtonsoft.Json.JsonConvert.SerializeObject(childList.Children));
                   var top=childList.Children.OrderBy(or=>or).First();
                   byte[] da=null;
                   if(path+"/"+top==tempNode)
                   {
                       tempNodeOut =tempNode;
                       da= GetDataAsync(path,null,true).Result.Data;
                        if(da==null||da.Length<1)
                        {
                            return string.Empty;
                        } 
                        return System.Text.Encoding.Default.GetString(da);
                   }
                   else
                   {
                    childList= GetChildrenAsync(path,new WaitLockWatch(autoResetEvent[1],this,_logger,path,tempNode),true).Result;
                    autoResetEvent[1].WaitOne();
                   }
                    _logger.LogDebug("继续执行。");
                    tempNodeOut =tempNode;
                    da= GetDataAsync(path,null,true).Result.Data;
                    if(da==null||da.Length<1)
                    {
                         return string.Empty;
                    }
                    return System.Text.Encoding.Default.GetString(da);
            }
            catch(Exception ep)
            {
                 _logger.LogError(ep,"获取同步锁出现错误。");
                if(!string.IsNullOrEmpty(tempNode))
                {
                    DeleteNode(tempNode,tempNode);  
                }
            }
            return null;
         }

         private void ReConn()
         {
             _logger.LogInformation("检查连接状态");
             if(_zookeeper.getState()==States.CLOSED
             ||_zookeeper.getState()== States.NOT_CONNECTED)
             {
                 _logger.LogInformation("连接为关闭，开始重新连接。");
                Conn(_zookeeperOptions);
             }
         }

         public void Close(string tempNode)
         {
             var task=Task.Run(async ()=>{ 
             requestLockSequence.Remove(tempNode); 
              await _zookeeper.closeAsync();
             });
             task.Wait(); 
         }
 
    }
}

前面的类如果了解了netcore的扩展服务和配置机制，就很简单理解了，我们主要是讲解这个服务类的功能。

首先看服务类其中的一段代码：

 private void Conn(ZookeeperOptions zookeeperOptions)
        {
            bool isReadOnly=default(Boolean);
            Wathcer=new WaitConnWatch(autoResetEvent[0],_logger); //监控连接是否连接成功
            if(isReadOnly!=zookeeperOptions.IsReadOnly)
            {
                isReadOnly=zookeeperOptions.IsReadOnly;
            }

            
            byte[] pwd=new byte[0];
            //如果没有密码和sessionId
            if(string.IsNullOrEmpty(zookeeperOptions.SessionPwd)
            &&_zookeeperOptions.SessionId==default(int))
            {
             _zookeeper=new ZooKeeper(zookeeperOptions.Connectstring,zookeeperOptions.SessionTimeout,Wathcer,isReadOnly);
            }
            else if (!string.IsNullOrEmpty(zookeeperOptions.SessionPwd))
            {
                pwd=System.Text.Encoding.Default.GetBytes(zookeeperOptions.SessionPwd);
                 _zookeeper=new ZooKeeper(zookeeperOptions.Connectstring,zookeeperOptions.SessionTimeout,Wathcer,0,pwd,isReadOnly);
            }
            else
            {
                 _zookeeper=new ZooKeeper(zookeeperOptions.Connectstring
                 ,zookeeperOptions.SessionTimeout,Wathcer,zookeeperOptions.SessionId,pwd,isReadOnly);
            }
             if(_zookeeper.getState()==States.CONNECTING)
            {
                _logger.LogDebug("当前状态：CONNECTING。阻塞等待");
                autoResetEvent[0].WaitOne();
            }
        }

这个方法是连接zookeeper，我们在构造函数中调用它，注意，zookeeper是异步，所以需要watcher类监控和AutoResetEvent阻塞当前线程，因为如果不阻塞，在连接还没建立的时候，后面调用，

会出现错误。在监控类被触发的时候，执行取消阻塞。

 internal class WaitConnWatch : Watcher
    {
        private AutoResetEvent _autoResetEvent;
        private ILogger _logger;

        public WaitConnWatch(AutoResetEvent autoResetEvent
        ,ILogger logger)
        {
            _autoResetEvent=autoResetEvent;
            _logger=logger;
        }

       public override Task process(WatchedEvent @event)
       {
           _logger.LogDebug("watch激发,回掉状态：{0}",@event.getState().ToString());
            if(@event.getState()== KeeperState.SyncConnected
            ||@event.getState()== KeeperState.ConnectedReadOnly)
            {
                _logger.LogDebug("释放阻塞");
                _autoResetEvent.Set();  //取消阻塞当前线程。
            }
            return Task.FromResult(0);
       }
    }

大家看zookeeper服务类，里面很多方法在执行前需要执行conn方法，这只是一种失败重连的机制，因为一般没有线程池的，我都会给这个服务单例。哪有人会问，如果失败重连，会不会阻塞当前应用，

这个不会，因为netcore是多线程的，但是会降低这个应用的生产力。我前面翻译过一篇net的关于线程的知识，后面也会单独一篇讲解netcore的线程模型。还有代码中我很少用异常去处理容错性，尽量抛出原生的异常，使用日志去记录，然后为这个类返回个null，异常对性能也有一定的消耗，当然看自己习惯了，目的都是为了应用的健壮性。

其他方法是操作zookeeper的类，大家可以看我贴出来的代码。因为zookeeper最出名的估计就是分布式锁了，所以就把这个功能加进来。

 public  string GetDataByLockNode(string path,string sequenceName,List<ACL> aclList,out string tempNodeOut)
         {
             _logger.LogInformation("获取分布式锁开始。");
             ReConn();
             string tempNode=string.Empty;
             tempNodeOut=string.Empty;

              if(_zookeeper.existsAsync(path).Result==null )
            {
                 _logger.LogDebug("path不存在");
                return null;
            }

            
            try
            {
                _logger.LogDebug("开始锁定语句块");
                lock(_lock)  //这是我为了防止重复提交做的防止并发，当然实际用的地方是协调应用之间的功能，而肯定不会用人机交互。你可以把这个看作多此一举。
                {
                     _logger.LogDebug("锁定，访问requestLockSequence的代码应该同步。");
                    tempNode=requestLockSequence
                    .Where(w=>w.StartsWith(path+"/"+sequenceName)).FirstOrDefault();
                   
                    if(tempNode==null)
                    {
                        tempNode=CreateZNode(path+"/"+sequenceName,"",CreateMode.EPHEMERAL_SEQUENTIAL,aclList).Result;
                        _logger.LogDebug("创建节点：{0}",tempNode);
                        if(tempNode==null)
                        {
                            _logger.LogDebug("创建临时序列节点失败。详细参数:path:{0},data:{1},CreateMode:{2}"
                            ,path+"/squence","",CreateMode.EPHEMERAL_SEQUENTIAL);
                            return null;
                        }
                         _logger.LogInformation("创建成功，加入requestLockSequence列表。");
                        requestLockSequence.Add(tempNode);
                    }
                    else
                    {
                        _logger.LogDebug("已经存在的锁节点，返回null");
                        return null;
                    }
                }

                var childList= GetChildrenAsync(path,null,true).Result;  //首先获取lock子节点。
                   if(childList==null||childList.Children==null||childList.Children.Count<1)
                   {
                        _logger.LogDebug("获取子序列失败，计数为零.path:{0}",path);
                        return null;
                   }
                   _logger.LogDebug("获取path:{0}的子节点：{1}",path,Newtonsoft.Json.JsonConvert.SerializeObject(childList.Children));
                   var top=childList.Children.OrderBy(or=>or).First();
                   byte[] da=null;
                   if(path+"/"+top==tempNode) //判断是否是当前自己的节点在队列顶端。
                   {
                       tempNodeOut =tempNode;
                       da= GetDataAsync(path,null,true).Result.Data;
                        if(da==null||da.Length<1)
                        {
                            return string.Empty;
                        } 
                        return System.Text.Encoding.Default.GetString(da);
                   }
                   else
                   {
                    childList= GetChildrenAsync(path,new WaitLockWatch(autoResetEvent[1],this,_logger,path,tempNode),true).Result; //如果自己不再队列顶端，则加监听等待这个节点有更改。
                    autoResetEvent[1].WaitOne();
                   }
                    _logger.LogDebug("继续执行。");
                    tempNodeOut =tempNode;
                    da= GetDataAsync(path,null,true).Result.Data;
                    if(da==null||da.Length<1)
                    {
                         return string.Empty;
                    }
                    return System.Text.Encoding.Default.GetString(da);
            }
            catch(Exception ep)
            {
                 _logger.LogError(ep,"获取同步锁出现错误。");
                if(!string.IsNullOrEmpty(tempNode))
                {
                    DeleteNode(tempNode,tempNode);  
                }
            }
            return null;
         }

接下来看监听类：

 internal class  WaitLockWatch:Watcher
    {
        private AutoResetEvent _autoResetEvent;
        private ILogger _logger;

        private string _path;

        private ZookeeperService _zookeeperService;

        public string _tempNode;

        public WaitLockWatch(AutoResetEvent autoResetEvent
        ,ZookeeperService zookeeperService
        ,ILogger logger,string path
        ,string tempNode)
        {
            _autoResetEvent=autoResetEvent;
            _zookeeperService=zookeeperService;
            _logger=logger;
            _path=path;
            _tempNode=tempNode;
        }

       public override Task process(WatchedEvent @event)
       {
           _logger.LogDebug("{0}节点下子节点发生改变，激发监视方法。",_path);
            var childList=_zookeeperService.GetChildrenAsync(_path,null,true).Result;
            if(childList==null||childList.Children==null||childList.Children.Count<1)
                   {
                        _logger.LogDebug("获取子序列失败，计数为零.path:{0}",_path);
                        return Task.FromResult(0);
                   }
                   var top=childList.Children.OrderBy(or=>or).First();
                   if(_path+"/"+top==_tempNode)   //判断当前节点是否队列顶端
                   {
                        _logger.LogDebug("释放阻塞");
                        _autoResetEvent.Set();
                   }
           
            return Task.FromResult(0);
       }
    }

这个类，在path节点每次更改或者子节点更改的时候都会激发，仅仅是判断当前节点是不是列表的顶端，再执行 _autoResetEvent.Set();释放阻塞让继续执行。

编译提交nuget，然后集成到测试程序看效果。

首先看zookeeper：

目前节点下没有一个子节点，再看看这个节点的值：

首先新建一个看看：

create -s -e /testzookeeper/sequence "" 

然后启动程序，当程序提交一个子节点，他是排序的：

我们删除我们刚刚用命令行创建的节点：

 delete /testzookeeper/sequence0000000072

然后再看值：

我们的客户端就是获取到锁后更改这个值，增加了一段字符串，客户端调用如下：

 [HttpGet("{id}")]
        public ActionResult<string> Get(int id)
        { 
            string sequenceNode=string.Empty;
            string nodename=_zookeeperService.GetDataByLockNode("/testzookeeper","sequence",ZooDefs.Ids.OPEN_ACL_UNSAFE,out  sequenceNode);
            if(sequenceNode==null)
            {
                return "获取分布式锁失败，请查看日志。";
            }
            
            _zookeeperService.SetDataAsync("/testzookeeper",nodename+"执行了"+DateTime.Now.ToString("yyyyMMddhhmmss"),false);
            if(!string.IsNullOrEmpty(sequenceNode))
            {
                _zookeeperService.DeleteNode(sequenceNode,sequenceNode);
                return "取得锁并且成功处理数据，释放锁成功。";
            }

            return "出现错误，请查日志。";
        }

当然这个是我做测试用的，实际开发，web就是用来做他的数据库存取的，尽量不要去做一些额外的功能，因为i守护进程或者后台服务和job有它自己的任务。