Asp.net core可以监视json、xml等配置文件的变化, 自动刷新内存中的配置内容, 但如果想每隔1秒从zookeeper、consul获取最新的配置信息, 需要自己实现.

阅读了 Asp.net core Document的Custom configuration provider, 得知只需要实现自己的IConfigurationSource和对应ConfigurationProvider即可

在这个示例中, 我建立了一个简单的option, 只包含一个不断变化的计数器变量.

public class RefreshableOptions
{
 public int IncreasementCount { get; set; }
}

实现IConfigurationSource和对应ConfigurationProvider, 内部有一个timer模拟从外部获取了最新的数据, 这里为简单起见, 采用硬编码的方式指定了option的路径

public class AutoRefreshConfigurationSource : IConfigurationSource
{
 public IConfigurationProvider Build(IConfigurationBuilder builder)
 {
 return new AutoRefreshConfigurationProvider();
 }
}

public class AutoRefreshConfigurationProvider : ConfigurationProvider
{
 private int count = 0;
 private bool isChanged;

 public AutoRefreshConfigurationProvider() : base()
 {
 Timer timer = new Timer(TimerCallback);
 timer.Change(1000, 3000);
 }

 public override void Load()
 {
 var beforeData = Data;
 // 这里采用硬编码指定option的路径
 Data = new Dictionary<string, string>() { { "AutoRefreshOptions:IncreasementCount", count.ToString() } };
 isChanged = IsDictionaryChanged(beforeData, Data);
 }

 private void TimerCallback(object state)
 {
 count++;
 this.Load();
 if (isChanged)
 {
 base.OnReload();//通知IConfiguration实例, 有参数发生了改变
 isChanged = false;
 }
 }
 //判断两个Idictionary是否有不同的帮助方法
 private static bool IsDictionaryChanged(IDictionary<string, string> before, IDictionary<string, string> after)
 {
 if (before == null && after == null)
 {
 return false;
 }
 if ((before == null) != (after == null))
 {
 return true;
 }
 if (before.Count != after.Count)
 {
 return true;
 }
 var ignoreCaseBefore = new Dictionary<string, string>(before, StringComparer.OrdinalIgnoreCase);
 foreach (var afterItemKey in after.Keys)
 {
 if (!ignoreCaseBefore.TryGetValue(afterItemKey, out var beforeItemValue))
 {
 return true;
 }
 if (beforeItemValue != after[afterItemKey])
 {
 return true;
 }
 ignoreCaseBefore.Remove(afterItemKey);
 }
 if (ignoreCaseBefore.Count > 0)
 {
 return true;
 }
 return false;
 }
}

实现扩展方法

public static class AutoRereshConfigurationExtensions
{
 public static IConfigurationBuilder AddAutoRereshConfiguration(this IConfigurationBuilder builder)
 {
 return builder.Add(new AutoRefreshConfigurationSource());
 }
}

使用方法

新建一个WebApi项目, 在Program.CreateWebHostBuilder中增加黄色部分

WebHost.CreateDefaultBuilder(args)
 .ConfigureAppConfiguration(config =>
 {
 config.AddAutoRereshConfiguration();
 })
 .UseStartup<Startup>();

在Startup. ConfigureServices中配置

services.Configure<RefreshableOptions>(Configuration.GetSection("AutoRefreshOptions"));

修改ValuesController

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
 private RefreshableOptions refreshableOptions;
 public ValuesController(IOptionsSnapshot<RefreshableOptions> refreshableOptions)
 {
 this.refreshableOptions = refreshableOptions.Value;
 }

 [HttpGet]
 public ActionResult<IEnumerable<string>> Get()
 {
 return new string[] { "value1", "value2", refreshableOptions.IncreasementCount.ToString() };
 }
}

启动后不停的刷新http://localhost:5000/api/values可以看到返回内容的变化

本文代码