2.【Spring Cloud Alibaba】实现负载均衡-Ribbon

负载均衡的两种方式

如何实现负载均衡

目前已经实现让A总能找到B，如何实现负载均衡

负载均衡的两种方式

• 服务器端负载均衡
• 客户端负载均衡

使用Ribbo实现负载均衡

Ribbon是什么

==Netflix开源的客户端侧负载均衡器==

引入Ribbon后的架构演进

整合Ribbon实现负载均衡

// 在spring容器中，创建一个对象，类型RestTemplate；名称/ID是：restTemplate
// <bean id="restTemplate" class="xxx.RestTemplate"/>
@Bean
@LoadBalanced
public RestTemplate restTemplate() {
    RestTemplate template = new RestTemplate();
    return template;
}

@Autowired
private RestTemplate restTemplate;

@GetMapping("/test-rest-template-sentinel/{userId}")
public UserDTO test(@PathVariable Integer userId) {
    return this.restTemplate
        .getForObject(
            "http://user-center/users/{userId}",
            UserDTO.class, userId);
}

Ribbon的组成

Ribbon内置的负载均衡规则

细粒度配置自定义

• Java代码配置
• 用配置属性配置
• 最佳实践总结

Java代码配置

@Configuration
@RibbonClient(name = "user-center",configuration = RibbonConfiguration.class)
public class UserCenterRibbonConfiguration {
}

@Configuration
public class RibbonConfiguration {
    @Bean
    public IRule ribbonRule() {
        return new NacosSameClusterWeightedRule();
    }
}

用配置属性配置

user-center:
  ribbon:
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule

两种方式对比

Ribbon全局配置

@Configuration
@RibbonClients(defaultConfiguration = RibbonConfiguration.class)
public class UserCenterRibbonConfiguration {
}

@Configuration
public class RibbonConfiguration {
    @Bean
    public IRule ribbonRule() {
        return new NacosSameClusterWeightedRule();
    }
}

Ribbon饥饿加载配置方式

ribbon:
  eager-load:
    enabled: true
    clients: user-center

扩展Ribbon-支持Nacos权重

import com.alibaba.nacos.api.exception.NacosException;
import com.alibaba.nacos.api.naming.NamingService;
import com.alibaba.nacos.api.naming.pojo.Instance;
import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.*;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.alibaba.nacos.NacosDiscoveryProperties;
import org.springframework.cloud.alibaba.nacos.ribbon.NacosServer;

@Slf4j
public class NacosWeightedRule extends AbstractLoadBalancerRule {
    @Autowired
    private NacosDiscoveryProperties nacosDiscoveryProperties;
    @Override
    public void initWithNiwsConfig(IClientConfig clientConfig) {
        // 读取配置文件，并初始化NacosWeightedRule
    }

    @Override
    public Server choose(Object key) {
        try {
            BaseLoadBalancer loadBalancer = (BaseLoadBalancer) this.getLoadBalancer();
//        log.info("lb = {}", loadBalancer);

            // 想要请求的微服务的名称
            String name = loadBalancer.getName();

            // 拿到服务发现的相关API
            NamingService namingService = nacosDiscoveryProperties.namingServiceInstance();

            // nacos client自动通过基于权重的负载均衡算法，给我们选择一个实例。
            Instance instance = namingService.selectOneHealthyInstance(name);

            log.info("选择的实例是：port = {}, instance = {}", instance.getPort(), instance);
            return new NacosServer(instance);
        } catch (NacosException e) {
            return null;
        }
    }
}

// spring cloud commons --> 定义了标准
// spring cloud loadbalancer --> 没有权重

扩展Ribbon-同一集群优先调用

import com.alibaba.nacos.api.exception.NacosException;
import com.alibaba.nacos.api.naming.NamingService;
import com.alibaba.nacos.api.naming.pojo.Instance;
import com.alibaba.nacos.client.naming.core.Balancer;
import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.AbstractLoadBalancerRule;
import com.netflix.loadbalancer.BaseLoadBalancer;
import com.netflix.loadbalancer.Server;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.alibaba.nacos.NacosDiscoveryProperties;
import org.springframework.cloud.alibaba.nacos.ribbon.NacosServer;
import org.springframework.util.CollectionUtils;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;

@Slf4j
public class NacosSameClusterWeightedRule extends AbstractLoadBalancerRule {
    @Autowired
    private NacosDiscoveryProperties nacosDiscoveryProperties;

    @Override
    public void initWithNiwsConfig(IClientConfig clientConfig) {

    }

    @Override
    public Server choose(Object key) {
        try {
            // 拿到配置文件中的集群名称 BJ
            String clusterName = nacosDiscoveryProperties.getClusterName();

            BaseLoadBalancer loadBalancer = (BaseLoadBalancer) this.getLoadBalancer();
            // 想要请求的微服务的名称
            String name = loadBalancer.getName();

            // 拿到服务发现的相关API
            NamingService namingService = nacosDiscoveryProperties.namingServiceInstance();

            // 1. 找到指定服务的所有实例 A
            List<Instance> instances = namingService.selectInstances(name, true);

            // 2. 过滤出相同集群下的所有实例 B
            List<Instance> sameClusterInstances = instances.stream()
                .filter(instance -> Objects.equals(instance.getClusterName(), clusterName))
                .collect(Collectors.toList());

            // 3. 如果B是空，就用A
            List<Instance> instancesToBeChosen = new ArrayList<>();
            if (CollectionUtils.isEmpty(sameClusterInstances)) {
                instancesToBeChosen = instances;
                log.warn("发生跨集群的调用, name = {}, clusterName = {}, instances = {}",
                    name,
                    clusterName,
                    instances
                );
            } else {
                instancesToBeChosen = sameClusterInstances;
            }
            // 4. 基于权重的负载均衡算法，返回1个实例
            Instance instance = ExtendBalancer.getHostByRandomWeight2(instancesToBeChosen);
            log.info("选择的实例是 port = {}, instance = {}", instance.getPort(), instance);

            return new NacosServer(instance);
        } catch (NacosException e) {
            log.error("发生异常了", e);
            return null;
        }
    }
}

class ExtendBalancer extends Balancer {
    public static Instance getHostByRandomWeight2(List<Instance> hosts) {
        return getHostByRandomWeight(hosts);
    }
}

扩展Ribbon-基于元数据的版本控制

元数据

元数据就是一堆的描述信息，以map存储。举个例子：

spring:
  cloud:
    nacos:
        metadata: 
          # 自己这个实例的版本
          version: v1
          # 允许调用的提供者版本
          target-version: v1

代码实现

@Slf4j
public class NacosFinalRule extends AbstractLoadBalancerRule {
    @Autowired
    private NacosDiscoveryProperties nacosDiscoveryProperties;

    @Override
    public Server choose(Object key) {
        // 负载均衡规则：优先选择同集群下，符合metadata的实例
        // 如果没有，就选择所有集群下，符合metadata的实例

        // 1. 查询所有实例 A
        // 2. 筛选元数据匹配的实例 B
        // 3. 筛选出同cluster下元数据匹配的实例 C
        // 4. 如果C为空，就用B
        // 5. 随机选择实例
        try {
            String clusterName = this.nacosDiscoveryProperties.getClusterName();
            String targetVersion = this.nacosDiscoveryProperties.getMetadata().get("target-version");

            DynamicServerListLoadBalancer loadBalancer = (DynamicServerListLoadBalancer) getLoadBalancer();
            String name = loadBalancer.getName();

            NamingService namingService = this.nacosDiscoveryProperties.namingServiceInstance();

            // 所有实例
            List<Instance> instances = namingService.selectInstances(name, true);

            List<Instance> metadataMatchInstances = instances;
            // 如果配置了版本映射，那么只调用元数据匹配的实例
            if (StringUtils.isNotBlank(targetVersion)) {
                metadataMatchInstances = instances.stream()
                        .filter(instance -> Objects.equals(targetVersion, instance.getMetadata().get("version")))
                        .collect(Collectors.toList());
                if (CollectionUtils.isEmpty(metadataMatchInstances)) {
                    log.warn("未找到元数据匹配的目标实例！请检查配置。targetVersion = {}, instance = {}", targetVersion, instances);
                    return null;
                }
            }

            List<Instance> clusterMetadataMatchInstances = metadataMatchInstances;
            // 如果配置了集群名称，需筛选同集群下元数据匹配的实例
            if (StringUtils.isNotBlank(clusterName)) {
                clusterMetadataMatchInstances = metadataMatchInstances.stream()
                        .filter(instance -> Objects.equals(clusterName, instance.getClusterName()))
                        .collect(Collectors.toList());
                if (CollectionUtils.isEmpty(clusterMetadataMatchInstances)) {
                    clusterMetadataMatchInstances = metadataMatchInstances;
                    log.warn("发生跨集群调用。clusterName = {}, targetVersion = {}, clusterMetadataMatchInstances = {}", clusterName, targetVersion, clusterMetadataMatchInstances);
                }
            }

            Instance instance = ExtendBalancer.getHostByRandomWeight2(clusterMetadataMatchInstances);
            return new NacosServer(instance);
        } catch (Exception e) {
            log.warn("发生异常", e);
            return null;
        }
    }

    @Override
    public void initWithNiwsConfig(IClientConfig iClientConfig) {
    }
}

public class ExtendBalancer extends Balancer {
    /**
     * 根据权重，随机选择实例
     *
     * @param instances 实例列表
     * @return 选择的实例
     */
    public static Instance getHostByRandomWeight2(List<Instance> instances) {
        return getHostByRandomWeight(instances);
    }
}

深入理解Nacos的Namespace

==服务调用不能跨namespace==