Asp.net core可以監視json、xml等配置文件的變化, 自動刷新內存中的配置內容, 但如果想每隔1秒從zookeeper、consul獲取最新的配置信息, 需要自己實現.

閱讀了 Asp.net core Document的Custom configuration provider, 得知只需要實現自己的IConfigurationSource和對應ConfigurationProvider即可

在這個示例中, 我建立了一個簡單的option, 只包含一個不斷變化的計數器變量.

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

實現IConfigurationSource和對應ConfigurationProvider, 內部有一個timer模擬從外部獲取了最新的數據, 這里為簡單起見, 采用硬編碼的方式指定了option的路徑

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;    // 這里采用硬編碼指定option的路徑    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實例, 有參數發生了改變      isChanged = false;    }  }  //判斷兩個Idictionary是否有不同的幫助方法  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;  }}

實現擴展方法

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

使用方法

新建一個WebApi項目, 在Program.CreateWebHostBuilder中增加黃色部分