In the microservices built by Spring Cloud, Ribbon, as a load balancer for service consumers, can be used in two ways: one is combined with RestTemplate, and the other is combined with feign (now closed source and not updated, replaced by OpenFeign officially provided by Spring Cloud, and the enhanced version of feign). Feign has integrated Ribbon by default.

RibbonRuleConfig, load balancing configuration class

/**
 * Method 1: configure load balancing policy
 * RibbonRuleConfig It cannot be scanned by @ ComponentScan of @ SpringBootApplication, otherwise it is the effect of global configuration
 */
@Configuration
public class RibbonRuleConfig {
    /**
     * Global configuration, specifying load balancing policy
     * @return
     */
    @Bean
    public IRule iRule(){//The method name must be iRule，Compliance is greater than configuration
        return new RandomRule();//Using random load balancing strategy
        //return new NacosRule();//Specify use Nacos Load balancing strategy provided (give priority to calling instances of the unified cluster based on random weight)
    }
}

Startup class:

@SpringBootApplication
@EnableDiscoveryClient//Can add or not, depending on the version, from Spring Cloud Edgware Start,@EnableDiscoveryClient Can be omitted. Just add relevant dependencies and configure them accordingly to register the microservice to the service discovery component.
//Multiple can be configured  RibbonRuleConfig Cannot be@SpringBootApplication of@ComponentScan Scan to, so put it to the next level, otherwise it will be the effect of global configuration
@RibbonClients(value = {
        @RibbonClient(name = "service-stock",configuration = RibbonRuleConfig.class)
})
public class ServiceOrderApplication {

    public static void main(String[] args) {
        SpringApplication.run(ServiceOrderApplication.class, args);
    }
}

Method 2: configuration file

application.properties

# apply name
spring.application.name=service-order
# Application service WEB access port
server.port=8040
# Nacos help document: https://nacos.io/zh-cn/docs/concepts.html
# Nacos certification information
spring.cloud.nacos.discovery.username=nacos
spring.cloud.nacos.discovery.password=nacos
# Nacos service discovery and registration configuration, where the sub attribute is server-addr appoint Nacos Server host and port
spring.cloud.nacos.discovery.server-addr=127.0.0.1:8848
# Register with the specified namespace of nacos. The default is public
spring.cloud.nacos.discovery.namespace=public

#Mode 2: load balancing profile
#Specify to use the load balancing policy provided by Nacos (call the same cluster instance first, based on random and weight)
service-stock.ribbon.NFLoadBalancerRuleClassName=com.alibaba.cloud.nacos.ribbon.NacosRule

5. Custom load balancing policy

Modify method 2. Do not use the official load balancing policy, and customize the load balancing configuration file

Custom load balancing policy rule CustomRule class:

/**
 * Method 2: Customize load balancing policy rules
 */
public class CustomRule extends AbstractLoadBalancerRule {

    /**
     * Initialize configuration information
     * @param iClientConfig
     */
    @Override
    public void initWithNiwsConfig(IClientConfig iClientConfig) { }

    /**
     * Load balancing policy rules. Take random numbers as an example here. You can write other rules or create new rules yourself
     * @param o
     * @return
     */
    @Override
    public Server choose(Object o) {
        ILoadBalancer  iLoadBalancer = this.getLoadBalancer();
        //Gets the currently requested service instance
        List<Server> reachableServers = iLoadBalancer.getReachableServers();
        //Generate random numbers based on service instances
        int random = ThreadLocalRandom.current().nextInt(reachableServers.size());
        //Get the service under this random number
        Server server = reachableServers.get(random);
        return server;
    }
}

application.properties

# apply name
spring.application.name=service-order
# Application service WEB access port
server.port=8040
# Nacos help document: https://nacos.io/zh-cn/docs/concepts.html
# Nacos certification information
spring.cloud.nacos.discovery.username=nacos
spring.cloud.nacos.discovery.password=nacos
# Nacos service discovery and registration configuration, where the sub attribute is server-addr appoint Nacos Server host and port
spring.cloud.nacos.discovery.server-addr=127.0.0.1:8848
# Register with the specified namespace of nacos. The default is public
spring.cloud.nacos.discovery.namespace=public

#Mode 2: load balancing profile
#Specify to use the load balancing policy provided by Nacos (call the same cluster instance first, based on random and weight)
#service-stock.ribbon.NFLoadBalancerRuleClassName=com.alibaba.cloud.nacos.ribbon.NacosRule
#Specify custom load balancing policy rule CustomRule class and use self-defined rules
service-stock.ribbon.NFLoadBalancerRuleClassName=com.qt.ribbon.rule.CustomRule

6. Replace the Ribbon with LoadBalancer

Currently, LoadBalancer only provides polling load policy.

Remove ribbon from nacos

Method 1, modify POM XML (recommended to prevent duplicate names of some classes):

<!-- nacos Service registration discovery (client) dependency -->
<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
    <!--remove ribbon support-->
    <exclusions>
        <exclusion>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </exclusion>
    </exclusions>
</dependency>

Method 2: modify the configuration file application properties:

# apply name
spring.application.name=service-order
# Application service WEB access port
server.port=8040
# Nacos help documentation: https://nacos.io/zh-cn/docs/concepts.html
# Nacos certification information
spring.cloud.nacos.discovery.username=nacos
spring.cloud.nacos.discovery.password=nacos
# Nacos service discovery and registration configuration, where the sub attribute server addr specifies the Nacos server host and port
spring.cloud.nacos.discovery.server-addr=127.0.0.1:8848
# Register with the specified namespace of nacos. The default is public
spring.cloud.nacos.discovery.namespace=public

#Do not use ribbon
spring.cloud.loadbalancer.ribbon.enabled=false

Add loadbalancer dependency

<!-- add to loadbalancer rely on-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

RestTemplateConfig class

/**
 * SpringBoot-RestTemplate Implementation calls third-party API s
 */
@Configuration
@Component
public class RestTemplateConfig {
    @Bean
    @LoadBalanced //Enable load balancing so that RestTemplate Request support for load balancing
    public RestTemplate restTemplate(RestTemplateBuilder builder){
        RestTemplate restTemplate = builder.build();
        return restTemplate;
    }
}

Access address: http://localhost:8040/order/addOrder