第一个Hystrix程序

一实际问题

数据查询失败怎么办？

二传统解决方式

1 添加超时机制

2 人肉运维

三容错框架Hystrix

Netflix提供了一个容错框架

四改造集群

五编写会员模块

1 编写控制器

package org.crazyit.cloud;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

    @RequestMapping(value = "/normalHello", method = RequestMethod.GET)
    public String normalHello() {
        return "Hello World";
    }

    @RequestMapping(value = "/errorHello", method = RequestMethod.GET)
    public String errorHello() throws Exception {
        Thread.sleep(10000);
        return "Error Hello World";
    }
}

2 启动会员模块

六编写销售模块

1 添加依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://maven.apache.org/POM/4.0.0http://maven.apache.org/xsd/maven-4.0.0.xsd">
      <modelVersion>4.0.0</modelVersion>
      <groupId>org.crazyit.cloud</groupId>
      <artifactId>first-hy-client</artifactId>
      <version>0.0.1-SNAPSHOT</version>
      
      <dependencies>
            <dependency>
                  <groupId>com.netflix.hystrix</groupId>
                  <artifactId>hystrix-core</artifactId>
                  <version>1.5.12</version>
            </dependency>
            <dependency>
                  <groupId>org.slf4j</groupId>
                  <version>1.7.25</version>
                  <artifactId>slf4j-log4j12</artifactId>
            </dependency>
            <dependency>
                  <groupId>commons-logging</groupId>
                  <artifactId>commons-logging</artifactId>
                  <version>1.2</version>
            </dependency>
            <dependency>
                  <groupId>org.apache.httpcomponents</groupId>
                  <artifactId>httpclient</artifactId>
                  <version>4.5.2</version>
            </dependency>
      </dependencies>
      
</project>

2 编写测试类

package org.crazyit.cloud;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class HttpClientMain {

    public static void main(String[] args) throws Exception {
        String url = "http://localhost:8080/normalHello";
        HttpGet httpget = new HttpGet(url);        
        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpResponse response = httpclient.execute(httpget);
        System.out.println(EntityUtils.toString(response.getEntity()));
    }

}

3 测试结果

Hello World

4 添加HelloCommand类

package org.crazyit.cloud;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommandGroupKey;

public class HelloCommand extends HystrixCommand<String> {

    public HelloCommand() {
        super(HystrixCommandGroupKey.Factory.asKey("TestGroup"));
    }

    protected String run() throws Exception {
        String url = "http://localhost:8080/normalHello";
        HttpGet httpget = new HttpGet(url);        
        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpResponse response = httpclient.execute(httpget);
        return EntityUtils.toString(response.getEntity());
    }

}

5 添加测试类

package org.crazyit.cloud;
public class NormalMain {
      public static void main(String[] args) {
            HelloCommand command = new HelloCommand();
            String result = command.execute();
            System.out.println(result);
      }
}

6 测试输出

Hello World

三添加回退逻辑

1 新增ErrorCommand类

package org.crazyit.cloud.error;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommandGroupKey;

public class ErrorCommand extends HystrixCommand<String> {

    public ErrorCommand() {
        super(HystrixCommandGroupKey.Factory.asKey("TestGroup"));
    }

    protected String run() throws Exception {
        String url = "http://localhost:8080/errorHello";
        HttpGet httpget = new HttpGet(url);        
        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpResponse response = httpclient.execute(httpget);
        return EntityUtils.toString(response.getEntity());
    }

    protected String getFallback() {
        System.out.println("fall back method");
        return "fall back hello";
    }
    
    
}

2 测试类

package org.crazyit.cloud.error;
public class ErrorMain {
      public static void main(String[] args) {
            ErrorCommand command = new ErrorCommand();
            String result = command.execute();
            System.out.println(result);
      }
}

3 测试结果

fall back method

fall back hello

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