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loadbalancer目前在springcloudcommons下

簡單的說就是將用戶的請求平攤的分配到多個服務上，從而達到系統的HA（高可用），常見的負載均衡有軟件Nginx，LVS，硬件 F5等

Spring Cloud LoadBalancer是由SpringCloud官方提供的一個開源的、簡單易用的 客戶端負載均衡器，它包含在SpringCloud-commons中用它來替換了以前的Ribbon組件。相比較于Ribbon，SpringCloud LoadBalancer不僅能夠支持RestTemplate，還支持WebClient（WeClient是Spring Web Flux中提供的功能，可以實現響應式異步請求）

看到兩個service已注冊成功， 但是consul的key/value之前配置未進行持久化保存，已經不存在

• 新建mydata文件夾
• 新建文件consul start.bat后綴為.bat

@echo.服務啟動......  
@echo off  
@sc create Consul binpath= "D:\devSoft\consul_1.17.0_windows_386\consul.exe agent -server -ui -bind=127.0.0.1 -client=0.0.0.0 -bootstrap-expect  1  -data-dir D:\devSoft\consul_1.17.0_windows_386\mydata   "
@net start Consul
@sc config Consul start= AUTO  
@echo.Consul start is OK......success
@pause

consul agent -server -config-dir=E:/consul/config -data-dir=E:/consul/data -bind=127.0.0.1 -bootstrap-expect=1 -ui

• cloud-payment-service-8001:http://localhost:8001/pay/get/info
• cloud-payment-service-8002:http://localhost:8002/pay/get/info

<!--loadbalancer-->
<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

cloud-payment-service 要與consul上注冊名稱一致。

@RestController
public class OrderController
{//public static final String PaymentSrv_URL = "http://localhost:8001";//先寫死，硬編碼public static final String PaymentSrv_URL = "http://cloud-payment-service";//服務注冊中心上的微服務名稱@Autowiredprivate RestTemplate restTemplate;/*** 一般情況下，通過瀏覽器的地址欄輸入url，發送的只能是get請求* 我們模擬消費者發送get請求，but底層調用post方法，客戶端消費者參數PayDTO可以不添加@RequestBody* @param payDTO* @return*/@GetMapping("/consumer/pay/add")public ResultData addOrder(PayDTO payDTO){return restTemplate.postForObject(PaymentSrv_URL + "/pay/add",payDTO,ResultData.class);}@GetMapping("/consumer/pay/get/{id}")public ResultData getPayInfo(@PathVariable Integer id){return restTemplate.getForObject(PaymentSrv_URL + "/pay/get/"+id, ResultData.class, id);}@GetMapping(value = "/consumer/pay/get/info")private String getInfoByConsul(){return restTemplate.getForObject(PaymentSrv_URL + "/pay/get/info", String.class);}
}

@Resource
private DiscoveryClient discoveryClient;
@GetMapping("/consumer/discovery")
public String discovery()
{List<String> services = discoveryClient.getServices();for (String element : services) {System.out.println(element);}System.out.println("===================================");List<ServiceInstance> instances = discoveryClient.getInstances("cloud-payment-service");for (ServiceInstance element : instances) {System.out.println(element.getServiceId()+"\t"+element.getHost()+"\t"+element.getPort()+"\t"+element.getUri());}return instances.get(0).getServiceId()+":"+instances.get(0).getPort();
}

默認兩種算法輪詢和隨機

public class RoundRobinLoadBalancer implementsReactorServiceInstanceLoadBalancer

從默認的輪詢，切換為 隨機算法，修改RestTemplateConfig

/*** LoadBalancer默認輪詢算法切換隨機算法* @LoadBalancerClient   @Bean*/
@Configuration
@LoadBalancerClient(//下面的value值大小寫一定要和consul里面的名字一樣，必須一樣value = "cloud-payment-service",configuration = RestTemplateConfig.class)
public class RestTemplateConfig
{@Bean@LoadBalanced //使用@LoadBalanced注解賦予RestTemplate負載均衡的能力public RestTemplate restTemplate(){return new RestTemplate();}@BeanReactorLoadBalancer<ServiceInstance> randomLoadBalancer(Environment environment,LoadBalancerClientFactory loadBalancerClientFactory) {String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);return new RandomLoadBalancer(loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);}
}

@LoadBalancerClient(name = "my-service", configuration = MyServiceLoadBalancerConfig.class)  
public class MyServiceConfiguration {  // 這里可以包含一些針對my-service的特定配置  
}  @Configuration  
public class MyServiceLoadBalancerConfig {  @Bean  public IRule myCustomRule() {  // 返回一個自定義的負載均衡規則  return new MyCustomRule();  }  
}