Steeltoe OSS整合了Netflix用java編寫的Circuit Breaker - Hystrix Netflix
https://github.com/Netflix/hystrix/wiki
為服務加了一層保護 提高強健度，本身還提供了精美的Dashboard
https://github.com/Netflix/Hystrix/wiki/Dashboard

Run Run Samples Run

跑Sample code之前請注意你電腦有安裝RabbitMQ, 官網沒有寫，
接下來的步驟會follow這個官方的文件
http://steeltoe.io/docs/steeltoe-circuitbreaker/#1-1-quick-start

啟動Eureka

先啟動Eureka, Eureka本身與Hystrix無關只是提供Sample code跑起來需要服務註冊與發現

git clone https://github.com/spring-cloud-samples/eureka.git
cd eureka
mvnw spring-boot:run

啟動Hystrix

接著啟動Hystrix Dashboard, 由於沒有提供mvnw所以Steeltoe OSS文件用的mvnw spring-boot:run是沒辦法跑的，直接使用jar

git clone https://github.com/spring-cloud-samples/hystrix-dashboard.git
mvn install
java -jar target/hystrix-dashboard-0.0.1.BUILD-SNAPSHOT.jar

打開 http://localhost:7979/ 會看到下面畫面

Sample code都在Samples\CircuitBreaker底下

啟動Fortune-Teller-Service

cd Samples/CircuitBreaker/src/AspDotNetCore/Fortune-Teller/Fortune-Teller-Service
dotnet restore --configfile nuget.config
dotnet run -f netcoreapp2.0  --server.urls http://*:5000

啟動Fortune-Teller-UI

SET BUILD=LOCAL or export BUILD=LOCAL
cd Samples/CircuitBreaker/src/AspDotNetCore/Fortune-Teller/Fortune-Teller-UI
dotnet restore --configfile nuget.config
dotnet run -f netcoreapp2.0  --server.urls http://*:5555

會看到連結到Hystrix Metrics connected! 就是成功了

info: Steeltoe.CircuitBreaker.Hystrix.MetricsStream.HystrixMetricsStreamPublisher[0]
      Hystrix Metrics starting
Hosting environment: Development
Content root path: C:\Users\ychu\Documents\Visual Studio 2017\Projects\Samples\CircuitBreaker\src\AspDotNetCore\FortuneTeller\Fortune-Teller-UI
Now listening on: http://*:5555
Application started. Press Ctrl+C to shut down.
info: Steeltoe.CircuitBreaker.Hystrix.MetricsStream.HystrixMetricsStreamPublisher[0]
      Hystrix Metrics connected!

打開Dashboard Monitor

打開Dashboard，在第一個欄位輸入 http://localhost:5555(服務位置)/hystrix/hystrix.stream
點Monitor Stream， 我期待我會看到

實際上我是看到....

人生總是不如想像....出現錯誤了

查log的可能性有:

• client端接到RabbitMQ有問題

  fail: Steeltoe.CircuitBreaker.Hystrix.MetricsStream.HystrixMetricsStreamPublisher[0]
      Error sending metrics to Hystrix dashboard, metrics streaming disabled: RabbitMQ.Client.Exceptions.AlreadyClosedException: Already closed: The AMQP operation was interrupted: AMQP close-reason, initiated by Peer, code=404, text="NOT_FOUND - no exchange 'spring.cloud.hystrix.stream' in vhost '/'", classId=60, methodId=40, cause=
         at RabbitMQ.Client.Impl.SessionBase.Transmit(Command cmd)
         at RabbitMQ.Client.Impl.ModelBase.ModelSend(MethodBase method, ContentHeaderBase header, Byte[] body)
         at RabbitMQ.Client.Impl.ModelBase.BasicPublish(String exchange, String routingKey, Boolean mandatory, IBasicProperties basicProperties, Byte[] body)
         at Steeltoe.CircuitBreaker.Hystrix.MetricsStream.HystrixMetricsStreamPublisher.<StartMetricsPublishing>b__11_0(List`1 jsonList)
  

• 應該要輸入的Url並非是官網所寫的http://localhost:5555/hystrix/hystrix.stream

  info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET http://localhost:5555/hystrix/hystrix.stream
  info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 16.6917ms 404
  

  所以404找不到對外的端口。

  結果猜測都是錯的，請見下篇Day22