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RoundRobinRule.java  源码剖析

/* * * Copyright 2013 Netflix, Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * */package com.netflix.loadbalancer;import com.netflix.client.config.IClientConfig;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import java.util.List;import java.util.concurrent.atomic.AtomicInteger;/** * The most well known and basic load balancing strategy, i.e. Round Robin Rule. * * @author stonse * @author Nikos Michalakis 
   
     * */public class RoundRobinRule extends AbstractLoadBalancerRule {    private AtomicInteger nextServerCyclicCounter;    private static final boolean AVAILABLE_ONLY_SERVERS = true;    private static final boolean ALL_SERVERS = false;    private static Logger log = LoggerFactory.getLogger(RoundRobinRule.class);    public RoundRobinRule() {        nextServerCyclicCounter = new AtomicInteger(0);    }    public RoundRobinRule(ILoadBalancer lb) {        this();        setLoadBalancer(lb);    }    public Server choose(ILoadBalancer lb, Object key) {        if (lb == null) {            log.warn("no load balancer");            return null;        }        Server server = null;        int count = 0;        while (server == null && count++ < 10) {            List
    
      reachableServers = lb.getReachableServers();            List
     
       allServers = lb.getAllServers();            int upCount = reachableServers.size();            int serverCount = allServers.size();            if ((upCount == 0) || (serverCount == 0)) {                log.warn("No up servers available from load balancer: " + lb);                return null;            }            int nextServerIndex = incrementAndGetModulo(serverCount);            server = allServers.get(nextServerIndex);            if (server == null) {                /* Transient. */                Thread.yield();                continue;            }            if (server.isAlive() && (server.isReadyToServe())) {                return (server);            }            // Next.            server = null;        }        if (count >= 10) {            log.warn("No available alive servers after 10 tries from load balancer: "                    + lb);        }        return server;    }    /**     * Inspired by the implementation of {@link AtomicInteger#incrementAndGet()}.     *     * @param modulo The modulo to bound the value of the counter.     * @return The next value.     */    private int incrementAndGetModulo(int modulo) {        for (;;) {            int current = nextServerCyclicCounter.get();            int next = (current + 1) % modulo;            if (nextServerCyclicCounter.compareAndSet(current, next))                return next;        }    }    @Override    public Server choose(Object key) {        return choose(getLoadBalancer(), key);    }    @Override    public void initWithNiwsConfig(IClientConfig clientConfig) {    }}
     
    
   

LoadBalancer.java

package com.dym.springcloud.lb;import org.springframework.cloud.client.ServiceInstance;import java.util.List;public interface LoadBalancer{    ServiceInstance instances(List
   
     serviceInstances);}
   

MyLB.java

package com.dym.springcloud.lb;import org.springframework.cloud.client.ServiceInstance;import org.springframework.stereotype.Component;import java.util.List;import java.util.concurrent.atomic.AtomicInteger;@Componentpublic class MyLB implements LoadBalancer{    private AtomicInteger atomicInteger = new AtomicInteger(0);    public final int getAndIncrement()    {        int current;        int next;        do {            current = this.atomicInteger.get();            next = current >= 2147483647 ? 0 : current + 1;        }while(!this.atomicInteger.compareAndSet(current,next));        System.out.println("*****第几次访问，次数next: "+next);        return next;    }    //负载均衡算法：rest接口第几次请求数 % 服务器集群总数量 = 实际调用服务器位置下标  ，每次服务重启动后rest接口计数从1开始。    @Override    public ServiceInstance instances(List
   
     serviceInstances)    {        int index = getAndIncrement() % serviceInstances.size();        return serviceInstances.get(index);    }}
   

OrderController.java

package com.dym.springcloud.controller;import com.dym.springcloud.entities.CommonResult;import com.dym.springcloud.entities.Payment;import com.dym.springcloud.lb.LoadBalancer;import lombok.extern.slf4j.Slf4j;import org.springframework.cloud.client.ServiceInstance;import org.springframework.cloud.client.discovery.DiscoveryClient;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RestController;import org.springframework.web.client.RestTemplate;import javax.annotation.Resource;import java.net.URI;import java.util.List;@RestController@Slf4jpublic class OrderController{    //public static final String PAYMENT_URL = "http://localhost:8001";    public static final String PAYMENT_URL = "http://CLOUD-PAYMENT-SERVICE";    @Resource    private RestTemplate restTemplate;    @Resource    private LoadBalancer loadBalancer;    @Resource    private DiscoveryClient discoveryClient;    @GetMapping("/consumer/payment/create")    public CommonResult
   
     create(Payment payment)    {        return restTemplate.postForObject(PAYMENT_URL +"/payment/create",payment,CommonResult.class);    }    @GetMapping("/consumer/payment/get/{id}")    public CommonResult
    
      getPayment(@PathVariable("id") Long id)    {        return restTemplate.getForObject(PAYMENT_URL+"/payment/get/"+id,CommonResult.class);    }    @GetMapping("/consumer/payment/getForEntity/{id}")    public CommonResult
     
       getPayment2(@PathVariable("id") Long id)    {        ResponseEntity
      
        entity = restTemplate.getForEntity(PAYMENT_URL+"/payment/get/"+id,CommonResult.class);        if(entity.getStatusCode().is2xxSuccessful()){            return entity.getBody();        }else{            return new CommonResult<>(444,"操作失败");        }    }    @GetMapping(value = "/consumer/payment/lb")    public String getPaymentLB()    {        List
       
         instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");        if(instances == null || instances.size() <= 0)        {            return null;        }        ServiceInstance serviceInstance = loadBalancer.instances(instances);        URI uri = serviceInstance.getUri();        return restTemplate.getForObject(uri+"/payment/lb",String.class);    }}
       
      
     
    
   

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