.NET Core 3.0之创建基于Consul的Configuration扩展组件 - 好文

写在前面

经过前面三篇关于.NET Core
Configuration的文章之后，本篇文章主要讨论如何扩展一个Configuration组件出来。如果前面三篇文章没有看到，可以点击如下地址访问

*
.NET Core 3.0之深入源码理解Configuration(一)
<https://www.cnblogs.com/edison0621/p/10854215.html>

*
.NET Core 3.0之深入源码理解Configuration(二)
<https://www.cnblogs.com/edison0621/p/10889325.html>

*
.NET Core 3.0之深入源码理解Configuration(三)
<https://www.cnblogs.com/edison0621/p/10891365.html>

了解了Configuration的源码后，再去扩展一个组件就会比较简单，接下来我们将在.NET Core
3.0-preview5的基础上创建一个基于Consul的配置组件。

相信大家对Consul已经比较了解了，很多项目都会使用Consul作为配置中心，此处也不做其他阐述了，主要是讲一下，创建Consul配置扩展的一些思路。使用Consul配置功能时，我们可以将信息转成JSON格式后再存储，那么我们在读取的时候，在体验上就像是从读取JSON文件中读取一样。

开发前的准备

初始化Consul

假设你已经安装并启动了Consul，我们打开Key/Value功能界面，创建两组配置选项出来，分别是commonservice和userservice，如下图所示

<https://img2018.cnblogs.com/blog/533598/201905/533598-20190525141703543-181117393.png>

配置值采用JSON格式

<https://img2018.cnblogs.com/blog/533598/201905/533598-20190525141704218-2144717142.png>

实现思路

我们知道在Configuration整个的设计框架里，比较重要的类ConfigurationRoot，内部又有一个IConfigurationProvider集合属性，也就是说我们追加IConfigurationProvider实例最终也会被放到到该集合中，如下图所示

<https://img2018.cnblogs.com/blog/533598/201905/533598-20190525141704760-1220559954.png>

该项目中，我使用到了一个已经封装好的Consul(V0.7.2.6)类库，同时基于.NET Core关于Configuration的设计风格，做如下的框架设计

<https://img2018.cnblogs.com/blog/533598/201905/533598-20190525141705304-1647877483.png>

考虑到我会在该组件内部创建ConsulClient实例，所以对ConsulClient构造函数的一部分参数做了抽象提取，并添加到了IConsulConfigurationSource中，以增强该组件的灵活性。

之前说过，Consul中的配置信息是以JSON格式存储的，所以此处使用到了Microsoft.Extensions.Configuration.Json.JsonConfigurationFileParser，用以将JSON格式的信息转换为Configuration的通用格式Key/Value。

核心代码

IConsulConfigurationSource
1: /// <summary> 2: /// ConsulConfigurationSource 3: /// </summary> 4:
public interface IConsulConfigurationSource : IConfigurationSource 5: { 6:
/// <summary> 7: /// CancellationToken 8: /// </summary> 9:
CancellationToken CancellationToken { get; } 10: 11: /// <summary> 12: ///
Consul构造函数实例，可自定义传入 13: /// </summary> 14: Action<ConsulClientConfiguration>
ConsulClientConfiguration { get; set; } 15: 16: /// <summary> 17: ///
Consul构造函数实例，可自定义传入 18: /// </summary> 19: Action<HttpClient>
ConsulHttpClient { get; set; } 20: 21: /// <summary> 22: ///
Consul构造函数实例，可自定义传入 23: /// </summary> 24: Action<HttpClientHandler>
ConsulHttpClientHandler { get; set; } 25: 26: /// <summary> 27: /// 服务名称
28: /// </summary> 29: string ServiceKey { get; } 30: 31: /// <summary>
32: /// 可选项 33: /// </summary> 34: bool Optional { get; set; } 35: 36:
/// <summary> 37: /// Consul查询选项 38: /// </summary> 39: QueryOptions
QueryOptions { get; set; } 40: 41: /// <summary> 42: /// 重新加载延迟时间，单位是毫秒
43: /// </summary> 44: int ReloadDelay { get; set; } 45: 46: /// <summary>
47: /// 是否在配置改变的时候重新加载 48: /// </summary> 49: bool ReloadOnChange { get;
set; } 50: }
ConsulConfigurationSource

该类提供了一个构造函数，用于接收ServiceKey和CancellationToken实例
1: public ConsulConfigurationSource(string serviceKey, CancellationToken
cancellationToken) 2: { 3: if (string.IsNullOrWhiteSpace(serviceKey)) 4: {
5: throw new ArgumentNullException(nameof(serviceKey)); 6: } 7: 8: this
.ServiceKey = serviceKey; 9: this.CancellationToken = cancellationToken; 10: }
其build()方法也比较简单，主要是初始化ConsulConfigurationParser实例
1: public IConfigurationProvider Build(IConfigurationBuilder builder) 2: {
3: ConsulConfigurationParser consulParser = new ConsulConfigurationParser(this);
4: 5: return new ConsulConfigurationProvider(this, consulParser); 6: }
ConsulConfigurationParser

该类比较复杂，主要实现Consul配置的获取、监控以及容错处理，公共方法源码如下
1: /// <summary> 2: /// 获取并转换Consul配置信息 3: /// </summary> 4: /// <param
name="reloading"></param> 5: /// <param name="source"></param> 6: ///
<returns></returns> 7: public async Task<IDictionary<string, string>>
GetConfig(bool reloading, IConsulConfigurationSource source) 8: { 9: try 10:
{ 11: QueryResult<KVPair> kvPair = await this.GetKvPairs(source.ServiceKey,
source.QueryOptions, source.CancellationToken).ConfigureAwait(false); 12: if
((kvPair?.Response ==null) && !source.Optional) 13: { 14: if (!reloading)
15: { 16: throw new
FormatException(Resources.Error_InvalidService(source.ServiceKey)); 17: } 18:
19: return new Dictionary<string, string>(); 20: } 21: 22: if
(kvPair?.Response ==null) 23: { 24: throw new
FormatException(Resources.Error_ValueNotExist(source.ServiceKey)); 25: } 26:
27: this.UpdateLastIndex(kvPair); 28: 29: return
JsonConfigurationFileParser.Parse(source.ServiceKey,new
MemoryStream(kvPair.Response.Value)); 30: } 31: catch (Exception exception)
32: { 33: throw exception; 34: } 35: } 36: 37: /// <summary> 38: ///
Consul配置信息监控 39: /// </summary> 40: /// <param name="key"></param> 41: ///
<param name="cancellationToken"></param> 42: /// <returns></returns> 43:
public IChangeToken Watch(string key, CancellationToken cancellationToken) 44:
{ 45: Task.Run(() => this.RefreshForChanges(key, cancellationToken),
cancellationToken); 46: 47: return this.reloadToken; 48: }

另外，关于Consul的监控主要利用了QueryResult.LastIndex属性，该类缓存了该属性的值，并与实获取的值进行比较，以判断是否需要重新加载内存中的缓存配置

ConsulConfigurationProvider

该类除了实现Load方法外，还会根据ReloadOnChange属性，在构造函数中注册OnChange事件，用于重新加载配置信息，源码如下：
1: public sealed class ConsulConfigurationProvider : ConfigurationProvider 2:
{ 3: private readonly ConsulConfigurationParser configurationParser; 4:
private readonly IConsulConfigurationSource source; 5: 6: public
ConsulConfigurationProvider(IConsulConfigurationSource source,
ConsulConfigurationParser configurationParser) 7: { 8: this
.configurationParser = configurationParser; 9: this.source = source; 10:
11: if (source.ReloadOnChange) 12: { 13: ChangeToken.OnChange( 14: () =>
this.configurationParser.Watch(this.source.ServiceKey, this
.source.CancellationToken), 15: async () => 16: { 17: await this
.configurationParser.GetConfig(true, source).ConfigureAwait(false); 18: 19:
Thread.Sleep(source.ReloadDelay); 20: 21: this.OnReload(); 22: }); 23:
} 24: } 25: 26: public override void Load() 27: { 28: try 29: { 30:
this.Data = this.configurationParser.GetConfig(false, this
.source).ConfigureAwait(false).GetAwaiter().GetResult(); 31: } 32: catch
(AggregateException aggregateException) 33: { 34: throw
aggregateException.InnerException; 35: } 36: } 37: }
调用及运行结果

此处调用在Program中实现
1: public class Program 2: { 3: public static void Main(string[] args) 4:
{ 5: CancellationTokenSource cancellationTokenSource = new
CancellationTokenSource(); 6: 7:
WebHost.CreateDefaultBuilder(args).ConfigureAppConfiguration( 8:
(hostingContext, builder) => 9: { 10: builder.AddConsul("userservice",
cancellationTokenSource.Token, source => 11: { 12:
source.ConsulClientConfiguration = cco => cco.Address =new Uri(
"http://localhost:8500"); 13: source.Optional = true; 14:
source.ReloadOnChange =true; 15: source.ReloadDelay = 300; 16:
source.QueryOptions =new QueryOptions 17: { 18: WaitIndex = 0 19: }; 20:
}); 21: 22: builder.AddConsul("commonservice",
cancellationTokenSource.Token, source => 23: { 24:
source.ConsulClientConfiguration = cco => cco.Address =new Uri(
"http://localhost:8500"); 25: source.Optional = true; 26:
source.ReloadOnChange =true; 27: source.ReloadDelay = 300; 28:
source.QueryOptions =new QueryOptions 29: { 30: WaitIndex = 0 31: }; 32:
}); 33: }).UseStartup<Startup>().Build().Run(); 34: } 35: }

运行结果，如下图所示，我们已经加载到了两个ConsulProvider实例，这与我们在Program中添加的两个Consul配置一致，其中所加载到的值也和.NET
Core Configuration的Key/Value风格相一致，所加载到的值也会Consul中所存储的相一致

<https://img2018.cnblogs.com/blog/533598/201905/533598-20190525142159337-171469605.png>

<https://img2018.cnblogs.com/blog/533598/201905/533598-20190525142200441-1807114625.png>

<https://img2018.cnblogs.com/blog/533598/201905/533598-20190525142338191-155181235.png>

总结

基于源码扩展一个配置组件出来，还是比较简单的，另外需要说明的是，该组件关于JSON的处理主要基于.NET
Core原生组件，位于命名空间内的System.Text.Json中，所以该组件无法在.NET Core
3.0之前的版本中运行，需要引入额外的JSON组件辅助处理。

源码已经托管于GitHub，地址：
https://github.com/littlehorse8/Navyblue.Extensions.Configuration.Consul
<https://github.com/littlehorse8/Navyblue.Extensions.Configuration.Consul>
，记得点个小星星哦

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