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Net Core 中有一个被.Net 基金会认可的库 Polly，可以用来简化熔断降级的处理。主要功能：重试（Retry）；断路器（Circuit-breaker）；超时检测（Timeout）；缓存（Cache）；降级（FallBack）；
官网：https://github.com/App-vNext/Polly
介绍文章：https://www.cnblogs.com/CreateMyself/p/7589397.html
Nuget安装指令：Install-Package Polly -Version 6.0.1
using System.Threading;using System.Threading.Tasks;using Daocfg;using Daocfg.Models.Account;using IBatisNet.DataMapper;using IBatisNet.DataMapper.Exceptions;using Polly;using Polly.CircuitBreaker;using Polly.Timeout;class PolicyTest ???{ ???????/// <summary> ???????/// mapper ???????/// </summary> ???????private static readonly ISqlMapper mapper; ???????private static readonly Dictionary<int, string> SqlErrorNumbers = new Dictionary<int, string> ???????????{ ???????????????{ -2, "超时时间已到。 超时时间在操作完成或服务器没有响应之前已过。" }, ???????????????{ -1, "在建立与服务器的连接时出错。 ?服务器不支持请求的协议 " }, ???????????????{ 2, "在建立与服务器的连接时出错。无法打开到 SQL Server 的连接" }, ???????????????{ 53, "在建立与服务器的连接时出错。无法打开到 SQL Server 的连接" ?}, ???????????}; ???????//触发熔断的连续错误阈值 ???????private static readonly int ExceptionsAllowedBeforeBreaking = 3; ???????//熔断的时间窗口 ???????private static readonly int DurationOfBreak = 5; ???????private static readonly Policy PolicyInstance; ???????static PolicyTest() ???????{ ???????????mapper = NewSqlMapper.Instance(); ???????????Policy mainPolicy = Policy.Handle<TimeoutException>() ???????????????????.Or<TimeoutRejectedException>(ex => true) ???????????????????.Or<WebException>(ex => ex.Status == WebExceptionStatus.Timeout) ???????????????????.Or<SqlException>(ex => SqlErrorNumbers.Keys.Contains(ex.Number)) ???????????????????.Or<DataMapperException>(ex => ex.Message.StartsWith("Unable to open connection", StringComparison.OrdinalIgnoreCase)) ???????????????????.CircuitBreaker(ExceptionsAllowedBeforeBreaking, TimeSpan.FromSeconds(DurationOfBreak), (exception, span, ???????????????????????arg3) => ???????????????????{ ???????????????????}, (context) => ???????????????????{ ???????????????????}); ???????????Policy policytimeout = Policy.Timeout(1, TimeoutStrategy.Pessimistic); ???????????PolicyInstance = mainPolicy.Wrap(policytimeout); ???????} ???????public static void Excute() ???????{ ???????????for (int i = 1; i <= 20; i++) ???????????{ ???????????????Console.WriteLine("当前为第" + i.ToString() + "次请求..."); ???????????????try ???????????????{ ???????????????????PolicyInstance.Execute(() => ???????????????????{ ???????????????????????Console.WriteLine("开始任务!"); ???????????????????????Thread.Sleep(1100); ???????????????????????var list = mapper.QueryForList<AccountDao>("qryAccount", new AccountFilter() ???????????????????????{ ???????????????????????????CustomerId = 1357, ???????????????????????}); ???????????????????????Console.WriteLine("完成任务!帐号信息:" + String.Join(",", list)); ???????????????????}); ???????????????} ???????????????catch (BrokenCircuitException ex) ???????????????{ ???????????????????Console.Write("触发熔断!"); ???????????????} ???????????????catch (Exception ex) ???????????????{ ???????????????????Console.WriteLine("execute出错" + ex.GetType().FullName); ???????????????} ???????????????Thread.Sleep(100); ???????????} ???????} ???}.NET熔断之Polly
原文地址：https://www.cnblogs.com/zhshlimi/p/10283710.html