.net framework 4.5 +steeltoe+ springcloud（三）实现Hystrix断路器

在基于.net framework的服务客户端实现断路器功能，基本项目创建步骤可以参照我的另一篇发现和调用服务的笔记，地址：http://www.cnblogs.com/troytian/p/8621861.html

在客户端能实现服务调用基础上，我们首先需要在appsettings.json中添加Hystrix配置：

 1 "hystrix": {
 2     "command": {
 3       "FortuneService": {
 4         "threadPoolKeyOverride": "FortuneServiceTPool"
 5       }
 6     },
 7     "stream": {
 8       "validate_certificates": false
 9     }
10   },

在程序入口对断路器进行注册：

 1  protected void Application_Start()
 2         {
 3             AreaRegistration.RegisterAllAreas();
 4             FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
 5             RouteConfig.RegisterRoutes(RouteTable.Routes);
 6             BundleConfig.RegisterBundles(BundleTable.Bundles);
 7  
 8             ApplicationConfig.RegisterConfig("development");
 9  
10             var builder = new ContainerBuilder();
11  
12             // Add Microsoft Options to container
13             builder.RegisterOptions();
14  
15             // Add Microsoft Logging to container
16             builder.RegisterLogging(ApplicationConfig.Configuration);
17  
18             // Add Console logger to container
19             builder.RegisterConsoleLogging();
20  
21             // Register all the controllers with Autofac
22             builder.RegisterControllers(typeof(MvcApplication).Assembly);
23  
24             // Register IDiscoveryClient, etc.
25             builder.RegisterDiscoveryClient(ApplicationConfig.Configuration);
26  
27             // Register FortuneService Hystrix command
28             builder.RegisterHystrixCommand<IFetchServise, FetchServise>("fetchServise", ApplicationConfig.Configuration);
29  
30             // Register Hystrix Metrics/Monitoring stream
31             //builder.RegisterHystrixMetricsStream(ApplicationConfig.Configuration);
32  
33             // Create the Autofac container
34             var container = builder.Build();
35             DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
36  
37             // Get a logger from container
38             var logger = container.Resolve<ILogger<MvcApplication>>();
39  
40             logger.LogInformation("Finished container build, starting background services");
41  
42             // Start the Discovery client background thread
43             container.StartDiscoveryClient();
44  
45             // Start the Hystrix Metrics stream 
46             //container.StartHystrixMetricsStream();
47  
48             logger.LogInformation("Finished starting background services");
49         }

然后需要修改服务调用的方式，添加断路器fallback回调功能，FetchServise.cs：

 1 public class FetchServise : HystrixCommand<string>, IFetchServise
 2     {
 3         DiscoveryHttpClientHandler _handler;
 4  
 5         private const string RANDOM_FORTUNE_URL = "http://java-service/hi?name=tian";
 6         private ILogger<FetchServise> _logger;
 7  
 8         public FetchServise(IHystrixCommandOptions options, IDiscoveryClient client, ILoggerFactory logFactory = null) : base(options)
 9         {
10             _handler = new DiscoveryHttpClientHandler(client, logFactory?.CreateLogger<DiscoveryHttpClientHandler>());
11             IsFallbackUserDefined = true;
12             _logger = logFactory?.CreateLogger<FetchServise>();
13         }
14  
15         public async Task<string> RandomFortuneAsync()
16         {
17             _logger?.LogInformation("RandomFortuneAsync");
18             var result = await ExecuteAsync();
19             _logger?.LogInformation("RandomFortuneAsync returning: " + result);
20             return result;
21         }
22  
23  
24         protected override async Task<string> RunAsync()
25         {
26             _logger?.LogInformation("RunAsync");
27             var client = GetClient();
28             var result = await client.GetStringAsync(RANDOM_FORTUNE_URL);
29             _logger?.LogInformation("RunAsync returning: " + result);
30             return result;
31         }
32  
33         protected override async Task<string> RunFallbackAsync()
34         {
35             _logger?.LogInformation("RunFallbackAsync");
36             return await Task.FromResult("服务断开，请稍后重试!");
37         }
38  
39  
40         private HttpClient GetClient()
41         {
42             var client = new HttpClient(_handler, false);
43             return client;
44         }
45     }