dubbo 负载均衡

官网：https://dubbo.apache.org/zh/docs/advanced/loadbalance/

负载均衡：消费端调用服务时，在路由过滤后的服务列表中使用负载均衡算法选择一个服务调用

负载均衡策略

# RandomLoadBalance：随机负载均衡
This class select one provider from multiple providers randomly.
 * You can define weights for each provider
随机选取一个可用服务，可以给服务设置权重
 
# RoundRobinLoadBalance：轮询
按照列表顺序选取服务，可对服务设置权重
 
# LeastActiveLoadBalance：最少连接数
Filter the number of invokers with the least number of active calls 
and count the weights and quantities of these invokers.
选取最少连接的服务，可对服务设置权重
 
# ConsistentHashLoadBalance：一致性hash
构建hash环，将请求放置在hash环上，
对请求hash，沿顺时针方向查找第一个服务节点，
参数相同的请求由相同的服务器处理，如果服务下线，请求会由原服务顺时针方向第一个可用的服务器处理；
同时添加虚拟节点，使得请求分散的更均匀
 
# ShortestResponseLoadbalance：最短响应时间
Filter the number of invokers with the shortest response time ofsuccess calls 
and count the weights and quantities of these invokers in last slide window.
选取最短响应时间的服务，并可设置权重

LoadBalance：负载均衡接口

@SPI(RandomLoadBalance.NAME)    //默认为RandomLoadBalance，随机选取
public interface LoadBalance {
 
    
    @Adaptive("loadbalance")
     Invoker select(List> invokers, URL url, Invocation invocation) throws RpcException;
 
}

@DubboReference：消费端服务调用注解

@documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.ANNOTATION_TYPE})
public @interface DubboReference {
 
    
    Class interfaceClass() default void.class;
 
    
    String interfaceName() default "";
 
    String group() default "";    //服务分组
    String version() default "";  //服务版本
 
    
    String url() default "";      //直连服务提供端（如果配置了，则不使用注册中心）
 
    
    String client() default "";   //客户端传输方式，默认为netty
 
    
    @Deprecated
    boolean generic() default false;   //已禁用
 
    
    @Deprecated
    boolean injvm() default true;      //已禁用
 
    
    boolean check() default true;
 
    
    boolean init() default true;
 
    
    boolean lazy() default false;
 
    
    boolean stubevent() default false;
 
    
    String reconnect() default "";
 
    
    boolean sticky() default false;
 
    
    String proxy() default "";
 
    
    String stub() default "";
 
    
    String cluster() default ClusterRules.EMPTY;
 
    
    int connections() default -1;
 
    
    int callbacks() default -1;
 
    
    String onconnect() default "";
 
    
    String ondisconnect() default "";
 
    
    String owner() default "";
 
    
    String layer() default "";
 
    
    int retries() default -1;
 
    
    String loadbalance() default LoadbalanceRules.EMPTY;    //负载均衡策略
 
    
    boolean async() default false;
 
    
    int actives() default -1;
 
    
    boolean sent() default false;
 
    
    String mock() default "";
 
    
    String validation() default "";
 
    
    int timeout() default -1;
 
    
    String cache() default "";
 
    
    String[] filter() default {};
 
    
    String[] listener() default {};
 
    
    String[] parameters() default {};
 
    
    @Deprecated
    String application() default "";
 
    
    String module() default "";
 
    
    String consumer() default "";
 
    
    String monitor() default "";
 
    
    String[] registry() default {};
 
    
    String protocol() default "";
 
    
    String tag() default "";
 
    
    String merger() default "";
 
    
    Method[] methods() default {};
 
    
    String id() default "";
 
    
    @Deprecated
    String[] services() default {};
 
    
    String[] providedBy() default {};
 
    
    String scope() default "";
 
    
    boolean referAsync() default false;
}

LoadBalancerRules：负载均衡枚举

public interface LoadbalanceRules {

    
    String RANDOM = "random";

    
    String ROUND_ROBIN = "roundrobin";

    
    String LEAST_ACTIVE = "leastactive";

    
    String CONSISTENT_HASH = "consistenthash";

    
    String SHORTEST_RESPonSE = "shortestresponse";

    String EMPTY = "";

}

HelloController

@RestController
public class HelloController {

    @DubboReference(loadbalance = LoadbalanceRules.ROUND_ROBIN)  //使用轮询负载均衡
    private HelloService helloService;

    @RequestMapping("/hello")
    public String hello(){
        helloService.hello().forEach(System.out::print);

        return "hello consumer 2";
    }
}